What sickness makes the legs swell? Understanding the causes of edema

September 24, 2025 •

4 min read

According to the Mayo Clinic, fluid retention in the body's tissues, or edema, is a common symptom with various potential causes. The question of "what sickness makes the legs swell" points to several underlying medical conditions, some of which require immediate attention to prevent serious health complications.

Quick Summary

Several medical conditions can cause leg swelling, or edema, including problems with the heart, kidneys, liver, or the circulatory system itself, such as deep vein thrombosis (DVT) or chronic venous insufficiency. Fluid buildup from these issues can signal a serious underlying health problem, making a proper diagnosis essential for effective treatment.

Key Points

Edema is the cause: Leg swelling, known as peripheral edema, is caused by excess fluid accumulation in tissues, not a specific sickness itself.
Heart, kidney, and liver disease are major causes: Organ dysfunction can disrupt the body's fluid balance, leading to noticeable swelling in the legs.
Circulatory issues like DVT and CVI are key culprits: Problems with blood flow, such as deep vein thrombosis (DVT) or chronic venous insufficiency (CVI), are common and serious causes.
Seek urgent care for certain symptoms: Sudden, one-sided leg swelling, redness, pain, or chest pain with swelling may indicate a DVT or heart issue and requires immediate medical attention.
Other causes include lifestyle and medication: Factors like prolonged sitting, high salt intake, pregnancy, obesity, and certain medications can also trigger leg swelling.
Accurate diagnosis is crucial for treatment: Since many conditions can cause swollen legs, a medical professional must diagnose the root cause to determine the correct treatment plan.

Understanding edema and its root causes

Leg swelling, medically known as peripheral edema, occurs when fluid leaks from small blood vessels (capillaries) into surrounding tissues, causing them to expand. While mild or temporary swelling can result from simple factors like standing for long periods, overconsumption of salt, or pregnancy, persistent or severe edema is often a symptom of a more serious underlying sickness. Addressing the root cause is crucial for effective treatment and preventing future complications.

Cardiovascular and circulatory issues

Swelling in the legs is a common indicator of problems affecting the heart and blood vessels. When the heart and veins are unable to properly pump blood, fluid can accumulate in the lower extremities due to gravity.

Heart failure

Congestive heart failure is a condition where the heart doesn't pump blood as efficiently as it should. As a result, blood can back up into the veins of the legs and feet, causing swelling or edema. Fluid can also build up in the abdomen (ascites) and lungs (pulmonary edema), leading to shortness of breath.

Chronic venous insufficiency (CVI)

In your legs, one-way valves inside your veins keep blood flowing upwards toward the heart. CVI occurs when these valves are damaged, causing blood to pool in the leg veins. This leads to increased pressure, forcing fluid to leak into the surrounding tissue and causing swelling, skin discoloration, and leg ulcers over time.

Deep vein thrombosis (DVT)

A deep vein thrombosis is a blood clot that forms in a deep vein, usually in the leg. This can cause sudden, painful swelling, along with warmth and redness in the affected leg. DVT is a serious medical emergency because the clot can break loose and travel to the lungs, causing a potentially fatal pulmonary embolism.

Kidney and liver diseases

When vital organs like the kidneys and liver are compromised, it disrupts the body's natural fluid balance, leading to edema.

Kidney disease

The kidneys are responsible for filtering waste and excess fluid from the blood. When kidney function is impaired, as with chronic kidney disease (CKD) or nephrotic syndrome, fluid and sodium build up in the body. This often manifests as swelling in the legs, as well as around the eyes.

Liver disease

The liver produces albumin, a protein that helps prevent fluid from leaking out of blood vessels. Liver damage, particularly advanced cirrhosis, can lead to insufficient albumin production. The resulting fluid imbalance can cause swelling in the legs and abdomen.

Lymphatic system dysfunction

The lymphatic system is a network of vessels that collect and return excess fluid to the bloodstream.

Lymphedema

Lymphedema occurs when there is a blockage or damage to the lymphatic system, preventing proper drainage of fluid. This causes a chronic buildup of fluid in the tissues, which can be seen in one or both legs. Lymphedema can be caused by surgery, cancer treatment involving lymph node removal, or it can be congenital.

Comparison of common causes of leg swelling


Condition	Cause of Swelling	Severity	Other Symptoms
Heart Failure	Inefficient heart pumping causes blood to back up into leg veins.	Can be life-threatening.	Shortness of breath, fatigue, rapid heartbeat.
Chronic Venous Insufficiency	Damaged vein valves cause blood to pool in the legs.	Can lead to painful skin ulcers.	Aching legs, skin discoloration, varicose veins.
Deep Vein Thrombosis (DVT)	A blood clot obstructs blood flow in a deep leg vein.	Medical emergency due to risk of pulmonary embolism.	Sudden pain, warmth, redness in one leg.
Kidney Disease	Impaired kidney function leads to fluid and sodium retention.	Serious, can progress to kidney failure.	Swelling around eyes, fatigue, changes in urination.
Liver Disease (Cirrhosis)	Low albumin production allows fluid to leak from blood vessels.	Indicates severe liver damage.	Abdominal swelling, jaundice, fatigue.
Lymphedema	Blocked lymphatic vessels prevent fluid drainage.	Chronic but manageable.	Heavy feeling in legs, thickened skin.

When to seek medical attention

While some minor leg swelling can be managed at home, certain symptoms warrant immediate medical evaluation. If your swelling is sudden, affects only one leg, or is accompanied by pain, warmth, or redness, you should seek emergency care immediately to rule out a DVT. Other warning signs include shortness of breath, chest pain, dizziness, or a rapid heart rate, which may indicate a serious cardiac or pulmonary issue. For any persistent, worsening, or unexplained swelling, a consultation with a healthcare provider is essential to diagnose the underlying cause and begin appropriate treatment.

Conclusion

Swollen legs, or edema, can be a sign of a wide range of health issues, from benign fluid retention to life-threatening conditions involving the heart, kidneys, and liver. Accurately identifying what sickness makes the legs swell requires professional medical evaluation. By understanding the different causes, symptoms, and risk factors, individuals can be more proactive about their health and seek timely care when needed. Managing an underlying condition is key to resolving persistent edema and improving overall well-being. For more information on health conditions and their symptoms, resources like the Mayo Clinic offer reliable, in-depth content.

Frequently Asked Questions

Swelling in only one leg is a potential symptom of a deep vein thrombosis (DVT), a serious condition caused by a blood clot. A localized injury or infection, such as cellulitis, can also cause unilateral swelling.

Edema is general swelling from excess fluid in body tissues, which can have various causes. Lymphedema is a specific, chronic type of edema caused by damage or blockage in the lymphatic system, preventing proper drainage.

Yes, high blood pressure can lead to other serious conditions, like heart or kidney disease, which, in turn, cause edema. Certain medications used to treat high blood pressure can also have leg swelling as a side effect.

Mild swelling in the legs and ankles is a common occurrence during pregnancy. However, sudden or severe swelling, particularly in the hands and face, could be a sign of preeclampsia and should be evaluated by a doctor.

For mild, temporary swelling, elevating the legs, wearing compression socks, and reducing salt intake can help. Light exercise can also improve circulation and prevent fluid from pooling.

Severe or sudden swelling, especially when confined to one leg, can be a medical emergency like DVT. Accompanied symptoms like pain, chest pain, fever, or shortness of breath also indicate a serious underlying condition.

Yes, some medications, including certain blood pressure drugs (calcium channel blockers), NSAIDs, steroids, and hormones, can cause leg swelling as a side effect.