Swollen legs, ankles and feet are most often caused by fluid building up in the tissues, called edema (or oedema). The cause may be minor, such as standing or sitting too long or eating salty food, or it may be a vein, clot, heart, kidney or liver problem. Swelling in just one leg, swelling that comes on suddenly, or swelling with chest pain or breathlessness needs medical attention, and the sections below explain which signs matter most.
What causes swollen legs and ankles?
The NHS page on oedema says swelling in the ankles, feet and legs is often caused by a build-up of fluid. Cleveland Clinic's edema page describes edema as what happens when fluid builds up faster than it can drain out. Harvard Health explains the gravity effect: when you are on your feet a lot, gravity pulls blood into the leg veins, and some of the water in the blood enters the tissues of your legs and feet.
| Cause | What the sources say |
|---|---|
| Standing or sitting too long | Named by the NHS, Cleveland Clinic, Harvard Health, Northwestern Medicine and WashU Medicine as a common, usually mild cause. |
| Too much salt | The NHS lists eating too much salty food. Cleveland Clinic names chips, processed meat, cheese, canned soup and fast food. |
| Pregnancy and hormones | Common in pregnancy. Harvard Health says severe swelling in pregnancy may be a sign of preeclampsia. CLS Health says swollen ankles around a period are common. |
| Being overweight | The NHS lists it. Northwestern Medicine says extra weight puts pressure on your veins, affecting blood flow. |
| Medicines | The NHS lists some blood pressure medicines, contraceptive pills, hormone therapy, antidepressants and steroids. Harvard Health and Northwestern Medicine name calcium-channel blockers. |
| Vein problems | Varicose veins and venous insufficiency. Harvard Health says the vein valves age and may work less efficiently. |
| Blood clot (DVT) | Clots in the deep leg veins block blood returning to the heart. Usually only one leg swells. |
| Heart failure | Harvard Health says blood that should return to the heart pools in the leg veins instead, and fluid leaks into the feet and lower legs. |
| Liver disease | Harvard Health says some liver disease can lower albumin, a protein made in the liver, so fluid passes into the tissues. This can swell the hands and face as well as the legs. |
| Kidney disease | Fluid can build up when the kidneys struggle to remove excess fluid. |
| Infection | Cellulitis, a bacterial skin infection, causes redness, swelling and pain, most commonly on the feet and legs. |
| Injury, bone and tendon problems | Sprains, fractures, arthritis and tendinitis. Harvard Health says these typically also cause pain. |
| Other | The NHS also lists thyroid problems and insect bites. Cleveland Clinic lists alcohol overuse, sleep apnea and lymphedema. |
Northwestern Medicine's vascular surgeon Gabriel A. Wallace, MD, says: “Sometimes lower extremity swelling is caused by more than one factor.” That is one reason the sources push for a proper assessment when swelling persists.
What causes swelling from the knee down?
The sources used here do not describe a separate set of causes for swelling that stops at the knee. They do explain why the lower legs and feet are affected so often. Gravity pulls fluid down, and Cleveland Clinic says edema “happens most often in your feet, ankles and legs.” What the sources stress is whether one leg or both are swollen. Swelling in one leg points toward different problems, such as a clot, an injury or an infection. Swelling in both legs more often fits gravity, salt, medicines, or vein, heart, kidney or liver conditions. Northwestern Medicine adds that chronic swelling in the left leg may be caused by May-Thurner syndrome, where the iliac vein in the pelvis is compressed.
When should you worry about swollen legs and feet?
The NHS splits its advice into three levels.
| Level | NHS signs |
|---|---|
| See a GP | Both ankles, feet or legs are swollen and it has not improved after treating it at home for a few days, it gets worse, or you have been diagnosed with a heart, kidney or leg vein condition. |
| Urgent GP appointment or NHS 111 | Swelling in 1 ankle, foot or leg with no known cause; a lot of swelling after an injury; swelling that is severe, painful or very sudden; swelling in the face or tummy too; a red or hot swollen area; a very high temperature or feeling hot, cold or shivery; or swollen feet, ankles or legs if you have diabetes. |
| Call 999 | Shortness of breath or struggling to breathe; chest that feels tight, heavy or painful; coughing up blood; more noticeable heartbeat (palpitations); feeling lightheaded, faint, confused, sick or clammy. The NHS says you could have a blood clot in your lungs and not to drive yourself to A&E. |
Other sources agree on the main points. Harvard Health says to report swelling that leaves an indentation when you press a finger into it, has developed suddenly, lasts more than a few days, affects just one foot, or comes with pain or skin discoloration. It adds that “new swelling of just one leg is always something to bring to your doctor.” Cleveland Clinic lists severe pain, fever, coughing or vomiting blood, one-limb swelling (especially a leg), jaundice, and a personal or family history of heart, lung, liver or kidney disease. It also says swelling with an allergic reaction, especially around the face or mouth, is a medical emergency. If a racing heartbeat is part of what you feel, see our guide to heart palpitations.
Are swollen legs and feet dangerous? Can edema kill you?
Often not. CLS Health says occasional swelling after standing, sitting, traveling or eating salty foods is usually not serious. But swelling can be a sign of a dangerous condition. Harvard Health says swelling “can be a red flag for a more serious underlying problem, such as heart failure, deep-vein thrombosis (a blood clot in a leg vein), kidney disease, or cirrhosis of the liver.” It says a leg clot “can be very serious if not diagnosed and treated promptly” because it can break loose and travel to the lungs, causing a pulmonary embolism, which “can cause breathlessness, pain with breathing, and even death.” Northwestern Medicine calls a pulmonary embolism life-threatening.
Cleveland Clinic says untreated edema decreases circulation and can lead to pressure wounds, wounds that heal slowly or not at all, and infected wounds that can spread and cause serious problems such as sepsis, bone infections and heart valve infections, or lead to amputations. It also lists shortness of breath and decreased blood flow to important organs among the risks. So the swelling itself is rarely the danger. The cause behind it and any complications are what matter.
How do you reduce swelling in your legs and ankles?
None of the sources offers a guaranteed quick fix. For mild swelling, the NHS says it “should go away on its own,” and lists things that may ease it:
- Raise your legs or the swollen area on a chair or pillows when you can.
- Get gentle exercise, like walking, to improve blood flow.
- Wear wide, comfortable shoes with a low heel and soft sole.
- Wash, dry and moisturise your feet to avoid infections.
- Do not stand or sit for long periods, and do not wear clothes, socks or shoes that are too tight.
Harvard Health says that with a little swelling, getting off your feet and propping them up “the swelling should disappear over several hours.” CLS Health suggests propping the feet above heart level for 15 to 30 minutes. Northwestern Medicine's Dr. Wallace says to elevate the legs at night or at least keep them flat with the body, and to put compression stockings on in the morning when the legs are less swollen.
Is walking good for swollen feet?
The NHS lists gentle exercise like walking to improve blood flow. Harvard Health says exercising your legs helps pump fluid back to the heart. CLS Health suggests short walking breaks, ankle flexes or calf raises if you sit or stand for long periods. Cleveland Clinic advises not sitting or standing for long periods without a short walk. One caution: if swelling is in one leg only, comes on suddenly, or comes with pain, redness or warmth, the sources say to get it checked as a possible clot, so do not just walk it off.
Do compression socks help?
Northwestern Medicine says compression stockings are often recommended for varicose veins, chronic venous insufficiency and swelling from sitting or standing too long. CLS Health says to ask a healthcare provider first if you have diabetes, circulation problems, significant leg pain or possible blood clot symptoms. Cleveland Clinic also says to ask your provider before using them.
How do you flush fluid out of your legs? What is the best diuretic?
The sources used here do not rank diuretics or name a best one. Cleveland Clinic lists “prescription diuretics (‘water pills') that help your body get rid of excess fluid” as one possible treatment, and says treatment mainly depends on the cause. That is a prescription decision for your clinician, because the cause (a clot, an infection, heart failure, a medicine side effect) changes what is safe. Cleveland Clinic also lists changes to medicines that cause or contribute to the swelling. Do not stop a medicine on your own. The NHS, CLS Health and Northwestern Medicine all say to talk to your doctor before changing medication.
What should you drink, and what should you not eat?
Drinks. Northwestern Medicine includes “Stay hydrated by drinking plenty of water” in its tips. CLS Health lists staying hydrated among things that may help. WashU Medicine lists dehydration among causes of mild, temporary swelling. The sources used here do not name any special drink that stops leg swelling. Cleveland Clinic lists alcohol overuse as a possible cause and quitting tobacco or drinking less alcohol among possible treatments.
Foods. Salt is the dietary factor the sources agree on. Cleveland Clinic names “chips, processed meat, cheese, canned soup and fast food” as foods with a lot of sodium. The NHS lists too much salty food as a cause. Harvard Health says a low-salt diet “may reduce fluid buildup and swelling.” Cleveland Clinic suggests asking your primary care provider for recommendations about what you eat. If you have heart, kidney or liver disease, your own clinician may give you more specific limits.
What vitamin or deficiency causes swollen legs?
The sources used here do not name a vitamin deficiency as a cause of leg swelling, and none says a vitamin removes swelling. The closest related finding is Harvard Health's: some liver diseases lead to low blood levels of albumin, a protein made in the liver, and low albumin lets fluid pass into the tissues. That is a protein problem tied to liver disease, not something a vitamin is described as fixing. Blood tests, which Northwestern Medicine says can check heart, kidney and liver function, are how a clinician looks for these causes. Northwestern Medicine also lists urine tests to check for protein loss.
How is leg edema treated and diagnosed?
Cleveland Clinic says treatment mainly depends on the cause, and that treating an underlying condition may help. Options it lists include a low-salt diet, adjusting activity, quitting tobacco or drinking less alcohol, anti-inflammatory medicines, prescription diuretics, ice for minor injuries, and treatment for sleep apnea.
Harvard Health says your doctor will take a medical history and do a physical examination that includes your heart and lungs, and may order blood and urine tests, a chest x-ray, an electrocardiogram or other tests. Northwestern Medicine describes ultrasound imaging to look for clots and a venous reflux ultrasound to see whether the veins are working properly. WashU Medicine's vascular surgeons list ultrasound, compression therapy, lifestyle guidance, and procedures to improve vein function or address blockages if necessary. Harvard Health's advice is “don't make your own diagnosis,” because swelling can be the first clue to heart failure or liver or kidney disease.
What if you saw a lymph-related supplement advertised?
The sources above cover medical causes of swelling, including lymphedema, which Northwestern Medicine describes as swelling from problems with the drainage of lymph node fluid. They say nothing about supplements as treatment. If you found a product called Lymph Tonic while researching, you can read about that product on our Lymph Tonic review page. Before taking any supplement for swelling, check with your clinician that it will not interfere with your medicines or hide a cause that needs treatment.
Quick answers
- One leg swollen, sudden, painful, red or warm: the sources say get medical care promptly.
- Both legs swollen with breathlessness or fatigue: Northwestern Medicine says this could be a sign of heart failure and needs prompt medical care.
- Mild swelling after a long day: sources describe rest, elevation, movement and less salt as common first steps.
- Swelling lasting more than a few days or not improving at home: the NHS and Harvard Health both say to see a doctor.
By UTCardiothoracicSurgery.com Editorial Team