Swollen legs and feet happen when fluid builds up in the tissues beneath your skin, a condition called peripheral edema. It’s one of the most common physical complaints, and the causes range from sitting too long on a flight to serious heart or kidney problems. The key to figuring out what’s behind your swelling is paying attention to whether it affects one leg or both, how quickly it appeared, and what other symptoms came with it.
How Fluid Ends Up in Your Tissues
Your body constantly moves fluid between your bloodstream and the surrounding tissues. Two opposing forces keep this in balance: pressure inside your blood vessels pushes fluid out, while proteins in your blood (especially one called albumin) pull fluid back in. When something tips that balance, fluid leaks into the spaces around your cells and stays there, producing visible swelling.
Several things can tip the balance. Anything that raises pressure inside your veins, like standing all day or a blockage in a vein, forces more fluid out. If your blood protein levels drop too low (below about 2 grams per deciliter), there isn’t enough pull to draw fluid back in. And when your body senses fluid shifting out of your blood vessels, your kidneys respond by holding onto more salt and water, which can make the swelling even worse.
Common Everyday Causes
Not all leg swelling signals a medical problem. Gravity alone can do it. When you sit or stand in one position for hours, blood pools in your lower legs and fluid seeps into surrounding tissue. Long flights, desk jobs, and car trips are classic triggers. The swelling is usually mild, affects both legs equally, and goes down after you elevate your feet or walk around.
Heat is another common culprit. In warm weather, your blood vessels widen to help cool your body, which increases pressure in leg veins and promotes fluid leakage. High salt intake amplifies this effect. Eating well above 2,000 milligrams of sodium per day encourages your kidneys to retain water, and much of that extra fluid ends up settling in your lower extremities by the end of the day.
Medications That Cause Swelling
If your swelling started shortly after beginning a new medication, the drug itself may be the reason. Blood pressure medications called calcium channel blockers are among the most frequent offenders. In one large study, nearly 39% of patients taking these drugs developed peripheral edema, typically within about eight weeks. Higher doses carried more risk: 42.5% of patients on the higher dose developed swelling compared to 33% on the lower dose.
Other medications known to cause leg and foot swelling include anti-inflammatory painkillers (like ibuprofen and naproxen), steroids, certain diabetes drugs, and some hormone therapies including estrogen. These drugs either cause your body to retain sodium and water or dilate blood vessels in ways that promote fluid leakage. If you suspect a medication, don’t stop it on your own, but it’s worth raising the question with whoever prescribed it.
Heart-Related Causes
Swelling in both legs that gets worse over days or weeks can be an early sign of heart failure, particularly when the right side of the heart is involved. When the right ventricle can’t pump blood efficiently to the lungs, blood backs up in the veins returning from your body. That backup raises pressure in leg veins and pushes fluid into surrounding tissues. You’ll typically notice it in your feet and ankles first, and it tends to be worse at the end of the day or after standing.
Other signs that heart function might be involved include shortness of breath (especially when lying flat or during mild exertion), unusual fatigue, and a feeling of fullness or swelling in your abdomen. If your swelling leaves a dent when you press on it with your finger, that’s called pitting edema, and it’s common in heart-related fluid retention. Doctors can check for heart failure with blood tests that measure specific proteins released by a stressed heart, along with imaging of the heart itself.
Vein Problems in the Legs
Chronic venous insufficiency, where the valves in your leg veins stop working properly, is one of the most common causes of persistent leg swelling. Healthy veins have one-way valves that push blood upward toward the heart. When those valves weaken or fail, blood flows backward and pools in the lower legs.
The condition tends to progress through recognizable stages. It may start with spider veins or visible varicose veins, then progress to noticeable swelling. Over time, the skin around the ankles can develop a brownish discoloration or become dry and itchy. In advanced cases, the skin breaks down and forms open sores (ulcers) that are slow to heal. The progression isn’t inevitable, though. Compression garments and staying active can slow things considerably if you catch it early.
When Only One Leg Swells
Swelling that appears suddenly in just one leg deserves prompt attention because it may indicate a blood clot in a deep vein, known as a DVT. Warning signs include a calf that’s noticeably larger than the other (a difference of more than 3 centimeters is a clinical red flag), tenderness along the inner thigh or calf, warmth, and redness. Your risk is higher if you’ve recently been immobile for an extended period, had surgery, have active cancer, or have a leg in a cast or brace. A DVT is a medical emergency because the clot can break loose and travel to the lungs.
Kidney and Liver Disease
Your kidneys regulate how much salt and water stay in your body. When kidney function declines, sodium and fluid accumulate, and swelling often appears in both legs, around the ankles, and sometimes around the eyes in the morning. The swelling tends to be symmetric and may come with other signs like foamy urine, decreased urine output, or fatigue.
Liver disease, particularly cirrhosis, causes swelling through a different mechanism. A damaged liver produces less albumin, the protein responsible for keeping fluid inside your blood vessels. When albumin levels fall, fluid leaks out easily and collects in the legs and abdomen. Liver-related swelling is often accompanied by visible abdominal bloating, yellowing of the skin or eyes, and easy bruising.
Swelling During Pregnancy
Some degree of leg and foot swelling is normal in pregnancy, especially in the third trimester. Your blood volume increases significantly, and the growing uterus puts pressure on the large veins returning blood from your legs. Mild, symmetric swelling that improves with elevation and rest is usually nothing to worry about.
The exception is preeclampsia, a serious pregnancy complication that typically develops after 20 weeks. Preeclampsia involves new-onset high blood pressure (140/90 or higher) along with signs that organs are under stress, such as protein in the urine, severe headaches, vision changes, or upper abdominal pain. Sudden, dramatic swelling, particularly in the face and hands along with the legs, can be one of its signs. Severe preeclampsia involves blood pressure of 160/110 or higher and requires immediate medical care.
What You Can Do at Home
For mild swelling without other concerning symptoms, several strategies can make a real difference. Elevating your legs above heart level for 15 to 20 minutes several times a day helps fluid drain back toward your core. Reducing your sodium intake to under 2,000 milligrams per day limits how much water your body holds onto. That means cutting back on processed foods, canned soups, deli meats, and restaurant meals, which are the biggest sources of hidden sodium in most diets.
Regular movement is one of the most effective tools. Walking contracts your calf muscles, which act as a pump to push blood upward through your veins. Even flexing your ankles repeatedly while seated helps. If you sit or stand for long stretches, taking a short walk every hour can prevent fluid from pooling.
Compression stockings provide steady, graduated pressure that supports your veins and discourages fluid from settling in your tissues. They come in different strengths: 15 to 20 mmHg is the mildest level, suitable for minor swelling and long travel days. A 20 to 30 mmHg stocking is the most commonly prescribed strength for moderate swelling and early venous insufficiency. Firmer options at 30 to 40 mmHg are used for more significant swelling or lymphatic problems, but these typically require a clinical fitting to ensure they work correctly and don’t cause harm.
Signs That Need Medical Attention
Swelling that appears suddenly in one leg, especially with pain or warmth, needs same-day evaluation to rule out a blood clot. Swelling accompanied by shortness of breath could point to a heart or lung problem and also warrants urgent attention.
For swelling that’s been building gradually, it’s worth seeing a doctor if it doesn’t improve with elevation and reduced salt intake, if it’s getting progressively worse, if pressing on the swollen area leaves a lasting indent, or if you notice skin changes like darkening, thickening, or open sores around your ankles. Swelling paired with unexplained weight gain, decreased urination, or fatigue also deserves investigation, since these patterns can point to heart, kidney, or liver problems that respond best to early treatment.