What causes diabetes?

During the digestive process, much of the food that is eaten is converted into glucose, commonly known as blood sugar. Glucose circulates in the bloodstream and is used as food for the body's cells. But the cells cannot absorb glucose alone. A hormone called insulin, which is produced in the pancreas, must first bind to the cell surface. When this occurs, cells of the body are activated and are able to absorb the glucose. This process returns the body's blood sugar to a normal level. Diabetes mellitus is a disorder that affects the body's ability to efficiently utilize blood glucose. In type 1 diabetes, the pancreas does not produce enough insulin, so glucose cannot be absorbed to refuel the cells. In type 2 diabetes, insulin is produced, but it does not work properly and the glucose is not absorbed consistently by the cells. Both types of diabetes have the same results: glucose is not absorbed by the cells. That is why people with diabetes have high blood sugar levels. Without proper absorption of glucose from the bloodstream, the cells are starving for food. Regardless of which type of diabetes a person may have, people with diabetes must monitor their blood sugar levels. Depending on the type and severity of the disease, diabetes can be managed with diet or with medication.

Where can I get more information about diabetes?

American Diabetes Association : Support tools and direction regarding diabetes and its management

Quick Facts: Diabetes - Merck Manuals Consumer Version

Q: What are the symptoms of diabetes?

Type 1 diabetes symptoms often start suddenly. You may:

Diabetes is a disease in which your blood sugar (glucose) levels are too high.

You get diabetes if your body's normal way of controlling blood sugar isn't working right.

There are 2 types of diabetes, type 1 and type 2
People with type 1 diabetes have to take insulin (type 1 is sometimes called insulin-dependent diabetes)
Some people with type 2 diabetes have to take insulin, but many can just take pills and change their diet
Both types of diabetes can cause serious long-term problems, like heart attacks Heart Attack A heart attack is when blood flow to part of your heart is suddenly blocked and some of your heart muscle dies. Doctors use the term myocardial infarction to refer to a heart attack. Myocardium... read more and strokes Stroke A stroke is a sudden brain problem that happens when a blood vessel in your brain either gets blocked or breaks open and bleeds. Part of your brain stops getting blood. Brain tissue that doesn't... read more
There is no cure for diabetes, but you can manage it by taking insulin or other medicine and changing what you eat

Blood sugar is:

Your body’s main source of energy

Blood sugar isn't just from sugar that's in your drinks or that you put on food. Blood sugar comes from all sorts of food, like:

Bread
Fruit
Pasta
Potatoes

These and many other foods contain carbohydrates. Your body turns carbohydrates into blood sugar.

Your body controls how much sugar gets from your blood into your body’s cells by using:

Insulin

Insulin is a hormone your body makes in the pancreas. The pancreas is an organ in your belly behind your stomach.

After you eat, your body absorbs food and your blood sugar increases. Your pancreas senses the higher blood sugar and starts putting out insulin. The insulin tells your body's cells to take in sugar from the blood. When the blood sugar is at the right level, your pancreas stops putting out insulin.

Diabetes involves a problem with insulin.

There are 2 main types of diabetes:

In type 1 diabetes, your pancreas doesn't make insulin because the cells that make it were destroyed
In type 2 diabetes, your pancreas makes plenty of insulin but your body’s cells don’t respond to the insulin the way they should

Eating sugary foods doesn't give you diabetes. However, eating so much that you get very overweight can give you type 2 diabetes.

Type 1 diabetes usually develops before age 30, typically in children and adolescents.

Type 2 diabetes can develop at any age but is more common in people who:

Are overweight or obese
Are age 30 or older
Have certain racial or ethnic backgrounds (in the United States: people who are Black, Asian, American Indian, or Hispanic get diabetes at a higher rate than other people)
Have family members who have type 2 diabetes

Some women get type 2 diabetes during pregnancy. This is called gestational diabetes Diabetes During Pregnancy Diabetes is a disease in which your blood sugar (glucose) levels are too high. Blood sugar is your body’s main source of energy. Your body breaks down all types of foods, including bread, fruit... read more .

Type 1 diabetes symptoms often start suddenly. You may:

Urinate (pee) a lot
Be very thirsty and drink a lot
Have belly pain (especially for children)
Eat more than you usually do but still lose weight
Have blurry vision
Feel sleepy or sick to your stomach

Sometimes a dangerous problem called diabetic ketoacidosis Diabetic Ketoacidosis Diabetes is a disease in which your blood sugar (glucose) levels are too high. Diabetic ketoacidosis is a serious complication of diabetes. It's often called DKA. With DKA, your blood sugar... read more happens. It starts suddenly and can be the first sign of diabetes in children. If you have diabetic ketoacidosis, you may:

Have breath that smells fruity and like nail polish remover
Breathe deeply and very fast
Feel sick to your stomach and throw up
Feel weak and tired all over

Type 2 diabetes symptoms may start slowly. You may not have symptoms for many years. When you do, you may notice you’re:

Urinating more often and in larger amounts
Drinking a lot more water

These symptoms get worse over weeks or months. You may also:

Feel very weak and tired all over
Have blurry vision
Get dehydrated (not have enough water in your body)

If your blood sugar stays high for a long time, it can cause many problems. Most of the problems happen because diabetes causes blood vessels to clog up. Clogged blood vessels don't let enough blood get to your organs. So, you may have:

Doctors will test your blood to check your:

Blood sugar levels

Usually doctors measure your blood sugar level first thing in the morning before you've eaten anything. That is called a fasting blood sugar. Doctors need to measure fasting blood sugar because the rest of the day your blood sugar goes up and down depending on how much you eat.

Fasting blood sugar levels:

Less than 100 is normal
100 to 125, you're at risk of diabetes
126 or higher, you have diabetes

Another test doctors might do is:

Hemoglobin A1C

Hemoglobin is a substance inside your red blood cells. It carries oxygen in your blood. Sugar in your blood attaches to hemoglobin and forms hemoglobin A1C.

The higher your blood sugar, the more hemoglobin A1C there is

Because hemoglobin A1C lasts a long time, the amount of it in your blood changes slowly. So your hemoglobin A1C level tells your doctor about your blood sugar levels over the past 2 to 3 months. People with a hemoglobin A1C level higher than 6.5% have diabetes.

There is no cure for diabetes. The goal of treatment is to keep blood sugar levels close to normal.

The better you control your blood sugar levels, the less likely you are to have complications

Treatment of diabetes involves:

A proper diet
Exercise
Losing weight if you're overweight
Medicines
Checking your blood sugar regularly

If you have diabetes, learn as much about it as you can. Talk to a nurse trained in diabetes education. The nurse can help you understand what to eat, how active to be, how to check your blood sugar levels, and how to adjust your insulin (if needed).

Your body can't respond to changes in your blood sugar level, so it's important to:

Eat meals and snacks at about the same time each day
Eat about the same amount each day
Limit carbohydrates (like bread) and fatty foods at each meal
Eat more vegetables and carbohydrates that break down slowly, like those in fruits, whole grains, and high-fiber foods
Limit processed foods, like candy, cookies, donuts, and pastries
Avoid sugary drinks, including soda, sweet iced tea, lemonade, fruit punch, and sports drinks
Limit alcoholic drinks to 1 per day if you’re female and 2 per day if you’re male

You should try to exercise some every day.

Working out can help you get to or stay at a healthy weight and control your sugar levels
Talk to your doctor or nurse to figure out how much you should work out and what kinds of activities are best for you
Because your blood sugar level goes down when you exercise, you may need to eat a snack or give yourself less insulin before a long workout

If you have type 2 diabetes, it's very important to try to lose weight if you're overweight.

Losing weight will help control your blood sugar

Sometimes, if you lose enough weight you may not need to take medicine.

If you have type 1 diabetes, losing weight doesn't help with your blood sugar levels. But excess weight isn't healthy for anyone.

You need to check your blood sugar level because your blood sugar level changes all the time based on:

What you eat
How active you are
Your stress level
If you have an infection
Medicines you’re taking
The time of day

If your blood sugar levels change significantly, you may need to change your diet or the medicine you take.

Your doctor will tell you when and how often to check your blood sugar. If you have type 1 diabetes, you usually need to check your blood sugar several times a day. If you have type 2 diabetes, you can check it less often.

Most often you'll check your blood sugar by:

Sticking your fingertip with a small, sharp tool called a lancet to get a drop of blood
Putting the drop of blood on a small plastic test strip
Putting the test strip in a small machine that reads blood sugar levels

Write down your blood sugar levels each time you check them so you can share the numbers with your doctor. Your doctor will use the numbers to tell you whether to change your medicines or your diet. If you don't check your blood sugar, it can get too high and no one will know.

Some people use a continuous glucose monitoring device—this uses a small sensor placed under your skin that shows the results of your blood sugar levels every few minutes on the screen of a small belt device worn like a cell phone.

Doctors can also check the amount of hemoglobin A1C in your blood every 3 to 6 months. This lets them see how well your blood sugar levels have been controlled over time.

If you have type 1 diabetes, you’ll need insulin (shots or inhaler)—you can learn how to change the amount of insulin based on checking your blood sugar levels
If you have type 2 diabetes, you’ll need to take medicine by mouth, but you may also need insulin

American Diabetes Association: Support tools and direction regarding diabetes and its management
JDRF: Global organization funding type 1 diabetes research
National Institute of Diabetes and Digestive and Kidney Diseases: Detailed information about diabetes and its complications