Merck Manual

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Andrea D. Thompson

, MD, PhD, University of Michigan;

Michael J. Shea

, MD, Michigan Medicine at the University of Michigan

Reviewed/Revised Aug 2022 | Modified Sep 2022
Topic Resources

Swelling is due to excess fluid in the tissues. The fluid is predominantly water.

Swelling may be widespread or confined to a single limb or part of a limb. Swelling is often in the feet and lower legs. However, people who are required to remain in bed for extended periods (bed rest) sometimes develop swelling in the buttocks, genitals, and back of the thighs. Women who lie on only one side may develop swelling in the breast they lie on. Rarely, a hand or an arm swells.

Sometimes a limb suddenly swells. More often, swelling develops slowly, beginning with weight gain, puffy eyes upon awakening in the morning, and tight shoes at the end of the day. Swelling may develop so gradually that people do not notice until the swelling is considerable. Sometimes people have a feeling of tightness or fullness. Other symptoms may be present depending on the cause of the swelling and may include shortness of breath or pain in the affected limb.

Causes of Swelling

Swelling that occurs throughout the body has different causes than swelling that is confined to a single limb or part of a limb.

Widespread swelling is most commonly caused by

These disorders all cause fluid retention, which is the cause of the swelling.

Another cause of swelling of the lower legs is pooling of blood in the legs. Many obese, middle-aged or older people normally have a small amount of swelling at the end of the day due to blood pooling. This swelling typically goes away by morning. Blood can also pool in the legs if the valves in the veins are widened or damaged (chronic venous insufficiency Chronic Venous Insufficiency and Post-Thrombotic Syndrome Chronic venous insufficiency is damage to leg veins that prevents blood from flowing normally. Post-thrombotic syndrome is chronic venous insufficiency that results from a blood clot in the... read more Chronic Venous Insufficiency and Post-Thrombotic Syndrome ) such as may occur in people who previously had blood clots in the legs. In such people, the swelling usually does not go away overnight.

Many women normally have some swelling during the later stages of pregnancy. However, women who have a large amount of swelling, particularly if swelling also involves the hands and face and is accompanied by high blood pressure, may have preeclampsia Preeclampsia and Eclampsia Preeclampsia is new high blood pressure or worsening of existing high blood pressure that is accompanied by excess protein in the urine and that develops after the 20th week of pregnancy. Eclampsia... read more , which can be dangerous.

Swelling that is confined to a single limb or part of a limb is most commonly caused by

Many disorders increase risk of blood clots in a vein. Most often, these clots develop in a leg vein but sometimes they occur in an arm vein. Blood clots in a vein can be dangerous if the clot breaks off and travels to the lungs, blocking an artery there (called pulmonary embolism Pulmonary Embolism ).

Cellulitis typically causes swelling of the skin over only part of a limb. Much less often, an infection deep under the skin or in the muscles can cause the whole limb to swell.

Sometimes, an allergic reaction causes swelling around areas such as the mouth (angioedema). Angioedema Angioedema Angioedema is swelling of areas of tissue under the skin, sometimes affecting the face and throat. Angioedema can be a reaction to a drug or other substance (trigger), a hereditary disorder... read more Angioedema can also be a hereditary disorder in which swelling comes and goes at irregular intervals.

Evaluation of Swelling

Although swelling may seem like a minor irritation, especially if it does not cause discomfort and goes away while a person is sleeping, it can be a symptom of a serious disorder. The following information can help people decide when a doctor's examination is needed and to know what to expect during the evaluation.

Warning signs

In people with swelling, certain symptoms and characteristics are cause for concern. They include

  • Sudden onset

  • Swelling of only one leg

  • Significant pain or tenderness

  • Shortness of breath

  • Coughing up blood

When to see a doctor

People who have warning signs should see a doctor right away. People without warning signs who have a history of heart, lung, or kidney disease or who are pregnant should see a doctor right away. Other people without warning signs should schedule a doctor's appointment as soon as possible.

What the doctor does

Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the swelling and the tests that may need to be done.

Doctors ask about the location and duration of the swelling and presence and degree of pain or discomfort. Women are usually asked whether they are pregnant or whether swelling seems related to menstrual periods. Doctors also ask whether the person has any disorders (for example, heart, liver, or kidney disorders) or takes any drugs (for example, minoxidil, nonsteroidal anti-inflammatory drugs, angiotensin-converting enzyme [ACE] inhibitors, or amlodipine and other calcium channel blockers) that are known to cause swelling. Doctors also ask about the amount of salt used in cooking and at the table because excess salt can make swelling worse, particularly in people with heart or kidney disorders.

Doctors look for symptoms that may indicate the cause of swelling. For example, people with heart failure Heart Failure may have shortness of breath during exertion or may wake at night with shortness of breath. People with swelling and easy bruising may have a liver disorder, and people who have recently had surgery or a cast on their leg may have deep vein thrombosis.

Doctors may ask people with swelling that is long lasting to keep a record of their daily weight so that increases in swelling are detected quickly.

During the physical examination, doctors pay particular attention to the area of swelling, but they also carefully examine the person for other signs. Doctors listen to the heart and lungs with the stethoscope because swelling may be a sign of a heart disorder.



For most people with widespread swelling, blood tests are done to evaluate the function of the kidneys and liver. A chest x-ray and echocardiography may be done evaluate the function of the heart. Urinalysis is usually also done to check for large amounts of protein, which can indicate nephrotic syndrome or, in pregnant women, preeclampsia. Other tests are done based on the suspected cause. For example, in people with isolated swelling in one leg, doctors may do ultrasonography to look for blockage of a vein in the leg.

Treatment of Swelling

Specific causes are treated (for example, anticoagulants [blood thinners] are given to people with blood clots in the legs). Any drugs that caused the swelling are stopped or changed if possible.

Because swelling itself is not harmful, doctors do not give water pills (diuretics) to people unless they are needed to treat the cause of the swelling (such as heart failure). However, some simple general measures, such as sitting with the legs elevated or limiting the amount of salt in the diet, sometimes help relieve swelling.

Key Points

  • Swelling may be widespread or confined to a single area.

  • The main causes of widespread swelling are heart, liver, and kidney disorders.

  • The main causes of swelling of a single limb are blood clots in a vein and an infection.

  • Sudden onset of swelling may indicate a serious disorder, so people should see a doctor right away.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Loniten, Rogaine
Katerzia, Norliqva, Norvasc
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