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Diabetes Mellitus +dI-u-!bE-tEz-!me-lu-tus

by Preeti Kishore, MD

Diabetes mellitus is a disorder in which blood sugar (glucose) levels are abnormally high because the body does not produce enough insulin to meet its needs.

  • Urination and thirst are increased, and people lose weight when they are not trying to.

  • Diabetes damages the nerves and causes problems with sensation.

  • Diabetes damages blood vessels and increases the risk of heart attack, stroke, and kidney failure.

  • Doctors diagnose diabetes by measuring blood sugar levels.

  • People with diabetes need to follow a diet that is low in carbohydrates and fat, exercise, and usually take drugs to lower blood sugar levels.

Diabetes is a disorder that affects the amount of sugar in the blood. There are many types of sugar. Some sugars are simple, and others are more complex. Table sugar (sucrose) is made of two simpler sugars called glucose and fructose. Milk sugar (lactose) is made of glucose and a simple sugar called galactose. The carbohydrates in bread, pasta, rice, and similar foods are long chains of different simple sugar molecules. Sucrose, lactose, carbohydrates, and other complex sugars must be broken down into their component simple sugars by enzymes in the digestive tract before the body can absorb them. Once the body absorbs simple sugars, it usually converts them all into glucose, which is the main source of fuel for the body. Glucose is the sugar that is transported through the bloodstream and taken up by cells. Blood "sugar" really means blood glucose.

Insulin , a hormone released from the pancreas, controls the amount of glucose in the blood. Glucose in the bloodstream stimulates the pancreas to produce insulin . Insulin allows glucose to move from the blood into the cells. Once inside the cells, glucose is converted to energy, which is used immediately, or the glucose is stored as fat or glycogen until it is needed.

The levels of glucose in the blood vary normally throughout the day. They rise after a meal and return to normal within about 2 hours after eating. Once the levels of glucose in the blood return to normal, insulin production decreases. The variation in blood glucose levels is usually within a narrow range, about 70 to 110 milligrams per deciliter (mg/dL) of blood in healthy people. If people eat a large amount of carbohydrates, the levels may increase more. People older than 65 years tend to have slightly higher levels, especially after eating.

If the body does not produce enough insulin to move the glucose into the cells, or if the cells stop responding normally to insulin , the resulting high levels of glucose in the blood and the inadequate amount of glucose in the cells together produce the symptoms and complications of diabetes.

Doctors often use the full name diabetes mellitus, rather than diabetes alone, to distinguish this disorder from diabetes insipidus, a relatively rare disorder that does not affect blood glucose levels but also causes increased urination (see Central Diabetes Insipidus).



Prediabetes is a condition in which blood glucose levels are too high to be considered normal but not high enough to be labeled diabetes. People have prediabetes if their fasting blood glucose level is between 101 mg/dL and 126 mg/dL or if their blood glucose level 2 hours after a glucose tolerance test is between 140 mg/dL and 200 mg/dL. Identifying people with prediabetes is important because the condition carries a higher risk for future diabetes as well as heart disease. Decreasing body weight by 5 to 10% through diet and exercise can significantly reduce the risk of developing future diabetes.

Type 1

In type 1 diabetes (formerly called insulin -dependent diabetes or juvenile-onset diabetes), more than 90% of the insulin -producing cells of the pancreas are permanently destroyed. The pancreas, therefore, produces little or no insulin . Only about 10% of all people with diabetes have type 1 disease. Most people who have type 1 diabetes develop the disease before age 30, although it can develop later in life.

Scientists believe that an environmental factor—possibly a viral infection or a nutritional factor during childhood or early adulthood—causes the immune system to destroy the insulin -producing cells of the pancreas. A genetic predisposition may make some people more susceptible to the environmental factor.

Type 2

In type 2 diabetes (formerly called non- insulin -dependent diabetes or adult-onset diabetes), the pancreas continues to produce insulin , sometimes even at higher-than-normal levels. However, the body develops resistance to the effects of insulin , so there is not enough insulin to meet the body’s needs.

Type 2 diabetes was once rare in children and adolescents but has recently become more common. However, it usually begins in people older than 30 and becomes progressively more common with age. About 27% of people older than 65 have type 2 diabetes. People of certain racial and ethnic backgrounds are at increased risk of developing type 2 diabetes: blacks, American Indians, and Hispanics who live in the United States have a twofold to threefold increased risk. Type 2 diabetes also tends to run in families.

Obesity is the chief risk factor for developing type 2 diabetes, and 80 to 90% of people with this disorder are overweight or obese. Because obesity causes insulin resistance, obese people need very large amounts of insulin to maintain normal blood glucose levels.

Certain disorders and drugs can affect the way the body uses insulin and can lead to type 2 diabetes. High levels of corticosteroids (due to Cushing disease or taking corticosteroid drugs) and pregnancy (gestational diabetes—see see Gestational diabetes) are the most common causes of altered insulin use. Diabetes also may occur in people with excess production of growth hormone (acromegaly) and in people with certain hormone-secreting tumors. Severe or recurring pancreatitis and other disorders that directly damage the pancreas can lead to diabetes.


The two types of diabetes have very similar symptoms. The first symptoms are related to the direct effects of high blood glucose levels. When the blood glucose level rises above 160 to 180 mg/dL, glucose spills into the urine. When the level of glucose in the urine rises even higher, the kidneys excrete additional water to dilute the large amount of glucose. Because the kidneys produce excessive urine, people with diabetes urinate large volumes frequently (polyuria). The excessive urination creates abnormal thirst (polydipsia). Because excessive calories are lost in the urine, people may lose weight. To compensate, people often feel excessively hungry. Other symptoms include blurred vision, drowsiness, nausea, and decreased endurance during exercise.

Type 1

In people with type 1 diabetes, the symptoms often begin abruptly and dramatically. A condition called diabetic ketoacidosis may quickly develop. Without insulin , most cells cannot use the glucose that is in the blood. Cells still need energy to survive, and they switch to a back-up mechanism to obtain energy. Fat cells begin breaking down, producing compounds called ketones. Ketones provide some energy to cells but also make the blood too acidic (ketoacidosis). The initial symptoms of diabetic ketoacidosis include excessive thirst and urination, weight loss, nausea, vomiting, fatigue, and—particularly in children—abdominal pain. Breathing tends to become deep and rapid as the body attempts to correct the blood’s acidity (see Acidosis). The breath smells like nail polish remover because of the smell of the ketones escaping into the breath. Without treatment, diabetic ketoacidosis can progress to coma and death, sometimes very quickly.

Type 2

People with type 2 diabetes may not have any symptoms for years or decades before they are diagnosed. Symptoms may be subtle. Increased urination and thirst are mild at first and gradually worsen over weeks or months. Eventually, people feel extremely fatigued, are likely to develop blurred vision, and may become dehydrated.

Sometimes during the early stages of diabetes, the blood glucose level is abnormally low at times, a condition called hypoglycemia (see Hypoglycemia).

Because people with type 2 diabetes produce some insulin , ketoacidosis does not usually develop even when type 2 diabetes is untreated for a long time. However, the blood glucose levels can become extremely high (often exceeding 1,000 mg/dL). Such high levels often happen as the result of some superimposed stress, such as an infection or drug use. When the blood glucose levels get very high, people may develop severe dehydration, which may lead to mental confusion, drowsiness, and seizures, a condition called nonketotic hyperglycemic-hyperosmolar syndrome . Currently, many people with type 2 diabetes are diagnosed by routine blood glucose testing before they develop such severely high blood glucose levels.


People with diabetes may experience many serious, long-term complications. Some of these complications begin within months of the onset of diabetes, although most tend to develop after a few years. Most of the complications gradually worsen. In people with diabetes, strictly controlling the levels of glucose in the blood makes these complications less likely to develop or worsen.

Most complications are the result of problems with blood vessels. Glucose levels that remain high over a long time cause both the small and large blood vessels to narrow. The narrowing reduces blood flow to many parts of the body, leading to problems. There are several causes of blood vessel narrowing. Complex sugar-based substances build up in the walls of small blood vessels, causing them to thicken and leak. Poor control of blood glucose levels also tends to cause the levels of fatty substances in the blood to rise, resulting in atherosclerosis (see Atherosclerosis) and decreased blood flow in the larger blood vessels. Atherosclerosis leads to heart attacks and strokes. Atherosclerosis is between 2 and 6 times more common and tends to occur at a younger age in people with diabetes than in people who do not have diabetes.

Over time, elevated levels of glucose in the blood and poor circulation can harm the heart, brain, legs, eyes, kidneys, nerves, and skin, resulting in angina, heart failure, strokes, leg cramps during walking (claudication), poor vision, kidney failure, damage to nerves (neuropathy), and skin breakdown.

Poor circulation to the skin can lead to ulcers and infections and causes wounds to heal slowly. People with diabetes are particularly likely to have ulcers and infections of the feet and legs. Too often, these wounds heal slowly or not at all, and amputation of the foot or part of the leg may be needed.

Did You Know...

  • People who can strictly control their blood glucose levels may be able to minimize or delay diabetes complications.

People with diabetes often develop bacterial and fungal infections, typically of the skin. When the levels of glucose in the blood are high, white blood cells cannot effectively fight infections. Any infection that develops tends to be more severe and takes longer to resolve.

Damage to the blood vessels of the eye can cause loss of vision (diabetic retinopathy—see Diabetic Retinopathy). Laser surgery can seal the leaking blood vessels of the eye and prevent permanent damage to the retina. Therefore, people with diabetes should have yearly eye examinations to check for early signs of damage.

The kidneys can malfunction, resulting in kidney failure that may require dialysis or kidney transplantation. Doctors usually check the urine of people with diabetes for abnormally high levels of protein (albumin), which is an early sign of kidney damage. At the earliest sign of kidney complications, people are often given angiotensin-converting enzyme (ACE) inhibitors, drugs that slow the progression of kidney damage.

Damage to nerves can manifest in several ways. If a single nerve malfunctions, an arm or leg may suddenly become weak. If the nerves to the hands, legs, and feet become damaged (diabetic polyneuropathy), sensation may become abnormal, and tingling or burning pain and weakness in the arms and legs may develop (see Polyneuropathy). Damage to the nerves of the skin makes repeated injuries more likely because people cannot sense changes in pressure or temperature.

Long-Term Complications of Diabetes

Tissue or Organ Affected



Blood vessels

Fatty material (atherosclerotic plaque) builds up and blocks large or medium-sized arteries in the heart, brain, legs, and penis.

The walls of small blood vessels are damaged so that the vessels do not transfer oxygen to tissues normally, and the vessels may leak.

Poor circulation causes wounds to heal poorly and can lead to heart attacks, strokes, gangrene of the feet and hands, erectile dysfunction (impotence), and infections.


The small blood vessels of the retina are damaged, leading to formation of new fragile blood vessels that tend to bleed.

Vision decreases, and ultimately, blindness occurs.


Blood vessels in the kidneys thicken.

Protein leaks into urine.

Blood is not filtered normally.

The kidneys malfunction, and ultimately, kidney failure occurs.


Nerves are damaged because glucose is not used normally and because the blood supply is inadequate.

Legs suddenly or gradually weaken.

People have reduced sensation, tingling, and pain in their hands and feet.

Autonomic nervous system

The nerves that control blood pressure and digestive processes are damaged.

Swings in blood pressure occur.

Swallowing becomes difficult.

Digestive function is altered, and sometimes nausea or bouts of diarrhea occur.

Erectile dysfunction develops.


Blood flow to the skin is reduced, and sensation is decreased, resulting in repeated injury.

Sores and deep infections (diabetic ulcers) develop.

Healing is poor.


White blood cell function is impaired.

People become more susceptible to infections, especially of the urinary tract and skin.

Connective tissue

Glucose is not used normally, causing tissues to thicken or contract.

Carpal tunnel syndrome and Dupuytren contracture develop.


The diagnosis of diabetes is made when people have abnormally high levels of glucose in the blood. Blood glucose levels are often checked during a routine physical examination. Checking the levels of glucose in the blood annually is particularly important in older people, because diabetes is so common in later life. People may have diabetes, particularly type 2 diabetes, and not know it. Doctors may also check blood glucose levels in people who have symptoms of diabetes such as increased thirst, urination, or hunger. Additionally, doctors may check blood glucose levels in people who have disorders that can be complications of diabetes, such as frequent infections, foot ulcers, and yeast infections.

To measure the blood glucose levels, a blood sample is usually taken after people have fasted overnight. However, it is possible to take blood samples after people have eaten. Some elevation of blood glucose levels after eating is normal, but even after a meal the levels should not be very high. Fasting blood glucose levels should never be higher than 126 mg/dL. Even after eating, blood glucose levels should not be higher than 200 mg/dL.

Doctors can also measure the level of a protein in the blood, hemoglobin A 1C (also called glycosylated or glycolated hemoglobin). Hemoglobin is the red, oxygen-carrying substance in red blood cells. When blood is exposed to high blood glucose levels over a period of time, glucose attaches to the hemoglobin and forms glycosylated hemoglobin. The hemoglobin A 1C level (reported as the percentage of hemoglobin that is A 1C ) reflects long-term trends in blood glucose levels rather than rapid changes. Measurements of hemoglobin A 1C can be used to diagnose diabetes when testing is done by a certified laboratory (not by instruments used at home or in a doctor's office). People with a hemoglobin A 1C level of 6.5% or more have diabetes. If the level is between 5.7 and 6.4, they have prediabetes.

Another kind of blood test, an oral glucose tolerance test, may be done in certain situations, such as when screening pregnant women for gestational diabetes (see Gestational diabetes) or when testing older people who have symptoms of diabetes but normal glucose levels when fasting. However, it is not routinely used for testing for diabetes, including in pregnant women at very low risk because the test can be very cumbersome. In this test, people fast, have a blood sample taken to determine the fasting blood glucose level, and then drink a special solution containing a large, standard amount of glucose. More blood samples are then taken over the next 2 to 3 hours and are tested to determine whether the glucose in the blood rises to abnormally high levels.

Did You Know...

  • Many people have type 2 diabetes and are not aware of it.


Diet, exercise, and education are the cornerstones of treatment of diabetes and often the first recommendations for people with mild diabetes. People who have very high blood glucose levels and people with type 1 diabetes (no matter their blood glucose levels) also require drugs. Because complications are less likely to develop if people with diabetes strictly control their blood glucose levels, the goal of diabetes treatment is to keep blood glucose levels within the normal range as much as possible. Treatment of high blood pressure and high cholesterol levels, which can contribute to circulation problems, can help prevent some of the complications of diabetes as well. A low dose of aspirin taken daily is also helpful to reduce the risk of heart attacks.

Experts recommend that people keep their blood glucose levels to between 70 and 130 mg/dL fasting (before meals) and to less than 180 mg/dL 2 hours after meals. Hemoglobin A 1c levels should be less than 7%. Because aggressive treatment to reach these goals increases the risk that blood glucose might go too low (hypoglycemia—see see Hypoglycemia), these goals are adjusted for some people in whom hypoglycemia is not desirable, such as older people. Some other goals are keeping systolic blood pressure less than 140 mm Hg and diastolic blood pressure less than 80 mm Hg. The level of low-density lipoprotein (LDL) cholesterol (the "bad" cholesterol) in the blood should be kept below 100 mg/dL.

People with diabetes benefit greatly from learning about the disorder, understanding how diet and exercise affect their blood glucose levels, and knowing how to avoid complications. A nurse trained in diabetes education can provide information about managing diet, exercising, monitoring blood glucose levels, and taking drugs.

It is helpful for people with diabetes to carry or wear medical identification (such as a bracelet or tag) to alert health care practitioners to the presence of diabetes. This information allows health care practitioners to start life-saving treatment quickly, especially in the case of injury or change in mental status.

Diet management is very important in people with both types of diabetes. Doctors recommend a healthy, balanced diet and efforts to maintain a healthy weight. People with diabetes can benefit from meeting with a dietitian or a diabetes educator to develop an optimal eating plan. Such a plan includes avoiding simple sugars, increasing dietary fiber, limiting portions of carbohydrate-rich and fatty foods (especially saturated fats), and avoiding long periods between meals to prevent hypoglycemia, particularly when the person is taking insulin . Drugs may often be needed to help control the level of cholesterol in the blood.

People with type 1 diabetes who are able to maintain a healthy weight may be able to avoid the need for large doses of insulin . People with type 2 diabetes may be able to avoid the need for all drugs by achieving and maintaining a healthy weight. Some people who have been unsuccessful in losing weight through diet and exercise may take drugs to help them lose weight or may even undergo stomach reduction (bariatric) surgery.

Appropriate amounts of exercise can also help people control their weight and maintain blood glucose levels within the normal range. Because blood glucose levels go down during exercise, people must be alert for symptoms of hypoglycemia. Some people need to eat a small snack during prolonged exercise, decrease their insulin dose, or both. People with diabetes should stop smoking and consume only moderate amounts of alcohol (up to one drink per day for women and two for men).

Diabetic ketoacidosis is a medical emergency because it can cause coma and death. Hospitalization, usually in an intensive care unit, may be necessary. Large amounts of fluids are given intravenously along with electrolytes, such as sodium, potassium, chloride, and phosphate, to replace those fluids and electrolytes lost through excessive urination. Insulin is generally given intravenously so that it works quickly and the dose can be adjusted frequently. Blood levels of glucose, ketones, and electrolytes are measured every few hours. Doctors also measure the blood’s acid level. Sometimes, additional treatments are needed to correct a high acid level. However, controlling the levels of glucose in the blood with insulin and replacing electrolytes usually allow the body to restore the normal acid-base balance.

Nonketotic hyperglycemic-hyperosmolar syndrome is treated much like diabetic ketoacidosis. Fluids and electrolytes must be replaced. The levels of glucose in the blood must be restored to normal levels gradually to avoid sudden shifts of fluid within the brain. The blood glucose levels tend to be more easily controlled than in diabetic ketoacidosis, and blood acidity problems are not severe.

Insulin Replacement Therapy

People with type 1 diabetes almost always require insulin therapy, and many people with type 2 diabetes require it as well. Insulin is injected into the skin. Insulin currently cannot be taken by mouth because insulin is destroyed in the stomach. A nasal spray form of insulin was available but has been discontinued. New forms of insulin , such as forms that can be taken by mouth or applied to the skin, are being tested.

Insulin is injected under the skin into the fat layer, usually in the arm, thigh, or abdominal wall. Small syringes with very thin needles make the injections nearly painless. An air pump device that blows the insulin under the skin is rarely used but can be helpful for people who cannot tolerate needles. An insulin pen, which contains a cartridge that holds the insulin , is a convenient way for many people to carry and use insulin , especially for people who take several injections a day outside the home. Another device is an insulin pump, which pumps insulin continuously from a reservoir through a small needle left in the skin. Additional doses of insulin can be released at programmed times, or release can be triggered as needed. The pump more closely mimics the way the body normally produces insulin . For some people, the pump offers an added degree of control, whereas others find wearing the pump inconvenient or develop sores at the needle site.

Insulin is available in three basic forms, divided by speed of onset and duration of action:

  • Rapid-acting insulin, such as regular insulin , is fast and short acting. Regular insulin reaches its maximum activity in 2 to 4 hours and works for 6 to 8 hours. Lispro, aspart, and glulisine insulins , special types of rapid-acting regular insulin , are the fastest of all, reaching maximum activity in about 1 hour and working for 3 to 5 hours. Rapid-acting insulin is often used by people who take several daily injections and is injected 15 to 20 minutes before meals or just after eating.

  • Intermediate-acting insulin (such as neutral protamine Hagedorn [NPH] or neutral protamine lispro [NPL] insulin ) starts to work in 1 to 3 hours, reaches its maximum activity in 6 to 10 hours, and works for 15 to 26 hours. This type of insulin may be used in the morning to provide coverage for the first part of the day or in the evening to provide coverage during the night.

  • Long-acting insulin (such as insulin glargine or detemir) has very little effect in the first few hours but provides coverage for 20 to 36 hours depending on which of these types is used.

Insulin preparations are stable at room temperature for months, allowing them to be carried, brought to work, or taken on a trip. Insulin should not, however, be exposed to extreme temperatures.

The choice of insulin is complex. The following factors are considered before deciding which insulin is best:

  • How willing and able people are to monitor their blood glucose levels and adjust their insulin dosage

  • How often people are willing to inject insulin

  • How varied daily activity is

  • How adept people are at learning about and understanding the disorder

  • How stable blood glucose levels are during the day and from day to day

The easiest regimen to follow is a single daily injection of an intermediate-acting insulin . However, such a regimen provides the least control over blood glucose levels and is, therefore, rarely the best approach. Stricter control may be achieved by combining two insulins —a rapid-acting and an intermediate-acting insulin —in one morning dose. This combination requires more skill, but it offers people greater opportunity to adjust the blood glucose levels. A second injection of one insulin or both may be taken at dinner or at bedtime. Strictest control is usually achieved by injecting a long-acting insulin in the morning or evening along with several additional injections of rapid-acting insulin during the day. Adjustments can be made as insulin needs change. Measuring blood glucose levels at various times during the day helps determine the adjustment. Although this regimen requires the most knowledge of the disorder and attention to the details of treatment, it is considered the best option for most people who are treated with insulin , especially people with type 1 diabetes.

Some people, especially older people, take the same amount of insulin every day. Other people adjust the insulin dose daily depending on their diet, exercise, and blood glucose patterns. In addition, insulin needs may change if people gain or lose weight or experience emotional stress or illness, especially infection.

Over time, some people develop resistance to insulin . Because the injected insulin is not exactly like the insulin the body manufactures, the body can produce antibodies to the insulin . Although this reaction is less common with newer insulin preparations, these antibodies may interfere with the insulin’s activity, requiring very large doses.

Insulin injections can affect the skin and underlying tissues. An allergic reaction, which occurs rarely, causes pain and burning, followed by redness, itchiness, and swelling around the injection site for several hours. More commonly, the injections either cause fat deposits, making the skin look lumpy, or destroy fat, causing indentation of the skin. Many people rotate the injection sites, for example, using the thigh one day, the stomach another, and an arm the next, to avoid these problems.

Insulin Replacement Therapy

Antihyperglycemic Drugs

Oral antihyperglycemic drugs can often lower blood glucose levels adequately in people with type 2 diabetes. However, they are not effective in type 1 diabetes. There are several types. Sulfonylureas (for example, glyburide) and meglitinides (for example, repaglinide) stimulate the pancreas to produce more insulin ( insulin secretagogues). Biguanides (for example, metformin) and thiazolidinediones (for example, rosiglitazone) do not affect the release of insulin but increase the body’s response to it ( insulin sensitizers). Doctors may prescribe one of these drugs alone or with a sulfonylurea drug. Another class of drug is the glucosidase inhibitors, such as acarbose, which work by delaying absorption of glucose in the intestine.

People with type 2 diabetes are often prescribed oral antihyperglycemic drugs if diet and exercise fail to lower the levels of glucose in the blood adequately. The drugs are sometimes taken only once a day, in the morning, although some people need two or three doses. More than one type of oral drug may be used if one is not adequate. If oral antihyperglycemic drugs cannot control blood glucose levels well enough, injections of insulin or glucagon-like peptide drugs alone or in combination with the oral drugs may be needed.

Antihyperglycemic Drugs


Number of Daily Doses

Some Side Effects



2 to 3


Increased acidity of body fluids (rare)

Liver failure (rare)

Extended-release metformin

1 to 2



1 to 2

Weight gain

Low blood glucose levels



Low sodium in blood



Low blood glucose levels




1 to 2



Low blood glucose levels

Low blood count (anemia)


1 to 2

Low blood glucose levels


Weight gain

Micronized glyburide

1 to 2

Low blood glucose levels


Weight gain


1 to 2

Low blood glucose levels




1 to 2

Low blood glucose levels


Low blood count




Minimal weight gain



Low blood glucose levels




Weight gain

Fluid retention (edema)


1 to 2

Weight gain

Fluid retention

Possible increase in heart attacks

Alpha-glucosidase inhibitors




Abdominal pain





Abdominal pain


Dipeptidyl peptidase-4 inhibitor



Upper respiratory infections


Inflamed pancreas



Upper respiratory infections

Urinary tract infections

Inflamed pancreas





Lung infections

Glucagon-like peptide agonist







Inflamed pancreas

Thyroid tumors




Amylin analog




Low blood glucose levels

Sodium-glucose co-transporter-2 (SGLT2) inhibitor



Increased cholesterol levels in the blood

Urinary tract infections

Genital fungal infections

Monitoring Treatment

Monitoring blood glucose levels is an essential part of diabetes care. People with diabetes must adjust their diet, exercise, and take drugs to control blood glucose levels. Monitoring blood glucose levels provides the information needed to make those adjustments. Waiting until symptoms of low or high blood glucose levels develop is a recipe for disaster.

Many things cause blood glucose levels to change:

  • Diet

  • Exercise

  • Stress

  • Illness

  • Drugs

  • Time of day

The blood glucose levels may jump after people eat foods they did not realize were high in carbohydrates. Emotional stress, an infection, and many drugs tend to increase blood glucose levels. Blood glucose levels increase in many people in the early morning hours because of the normal release of hormones (growth hormone and corticosteroids), a reaction called the dawn phenomenon. And blood glucose may shoot too high if the body releases certain hormones in response to low blood glucose levels (Somogyi effect). Exercise may cause the levels of glucose in the blood to fall low, requiring that additional carbohydrates be consumed.

Blood glucose levels can be measured easily at home or anywhere. Most blood glucose monitoring devices (glucose meters) use a drop of blood obtained by pricking the tip of the finger with a small lancet. The lancet holds a tiny needle that can be jabbed into the finger or placed in a spring-loaded device that easily and quickly pierces the skin. Most people find that the pricking causes only minimal discomfort. Then, a drop of blood is placed on a reagent strip. In response to glucose, the reagent strip undergoes some chemical changes. A machine reads the changes in the test strip and reports the result on a digital display. Most of these machines time the reaction and read the result automatically. Some devices allow the blood sample to be obtained from other sites, such as the palm, forearm, upper arm, thigh, or calf. The machines are smaller than a deck of cards.

Continuous glucose monitoring (CGM) systems use a small glucose sensor placed under the skin. The sensor measures blood glucose levels every few minutes and displays the results on the screen of a small belt monitor worn like a cell phone. It also records results for the doctor to review. Alarms on the CGM can be set to sound when blood glucose levels drop too low or climb too high, so the device can help people quickly identify worrisome changes in blood glucose. Disadvantages of this device are that it must be calibrated several times a day with the results from a fingerstick blood glucose meter, it may irritate the skin, and it is somewhat large. Additionally, because the results are not reliable enough to guide treatment, a fingerstick glucose measurement must still be done before the person takes insulin . CGMs have not been shown to be better than fingerstick glucose meters used alone, Moreover, since fingerstick glucose measurements are still required, this device is not useful for most people with diabetes. However, CGMs are helpful in certain circumstances, such as in people with type 1 diabetes who have frequent, rapid changes in blood glucose (particularly when the glucose levels sometimes go very low), which are difficult to identify with fingerstick testing.

Most people with diabetes should keep a record of their blood glucose levels and report them to their doctor or nurse for advice in adjusting the dose of insulin or the oral antihyperglycemic drug. Many people can learn to adjust the insulin dose on their own as necessary.

Although urine can also be tested for the presence of glucose, checking urine is not a good way to monitor treatment or adjust therapy. Urine testing can be misleading because the amount of glucose in the urine may not reflect the current level of glucose in the blood. Blood glucose levels can get very low or reasonably high without any change in the glucose levels in the urine.

Doctors can monitor treatment using a blood test called hemoglobin A 1C . When the blood glucose levels are high, changes occur in hemoglobin, the protein that carries oxygen in the blood. These changes are in direct proportion to the blood glucose levels over an extended period. Thus, unlike the blood glucose measurement, which reveals the level at a particular moment, the hemoglobin A 1C measurement demonstrates whether the blood glucose levels have been controlled over the previous few months. People with diabetes aim for a hemoglobin A 1C level of less than 7%. Achieving this level is difficult, but the lower the hemoglobin A 1C level, the less likely people are to have complications. Levels above 9% show poor control, and levels above 12% show very poor control. Most doctors who specialize in diabetes care recommend that hemoglobin A 1C be measured every 3 to 6 months. Fructosamine, an amino acid that has bonded with glucose, is also useful for measuring blood glucose control over a period of a few weeks and is generally used when hemoglobin A 1C results are not reliable, such as in people who have abnormal forms of hemoglobin.

Monitoring and Preventing Complications

At the time of diagnosis and then at least yearly, people are monitored for the presence of diabetes complications, such as kidney, eye, and nerve damage. Worsening of complications can be prevented or delayed by strict blood glucose control or by early drug treatment. Risk factors for heart problems, such as increased blood pressure and high cholesterol levels, are evaluated at each doctor visit and are treated with drugs if necessary. Another common problem in people with diabetes is gum disease (gingivitis), and regular visits to the dentist for cleaning and preventive care are important.

Experimental Treatments

Experimental treatments are also showing promise for the treatment of type 1 diabetes. In one such treatment, insulin -producing cells are transplanted into body organs. This procedure is not yet routinely done, however, because immunosuppressant drugs must be given to prevent the body from rejecting the transplanted cells. Newer techniques may make suppression of the immune system unnecessary.

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