Swollen feet happen when fluid builds up in the tissues of your lower extremities, a condition called edema. Gravity pulls blood and fluid downward throughout the day, and your body relies on muscle movement, vein valves, and organ function to push that fluid back up. When any part of that system falters, or when outside factors tip the balance, fluid pools in your feet and ankles. The causes range from something as simple as sitting too long to serious conditions that need medical attention.
How Fluid Ends Up in Your Feet
Your circulatory system constantly moves fluid between your blood vessels and surrounding tissues. The balance depends on pressure inside your veins, the concentration of proteins in your blood (which pull fluid back into vessels), and how well your heart and kidneys regulate fluid volume. When venous pressure rises, protein levels drop, or your body holds onto too much sodium, the equation shifts and fluid leaks into tissues. Because your feet are the lowest point on your body, that’s where gravity deposits the excess.
Everyday Causes of Foot Swelling
Most foot swelling isn’t dangerous. It comes from routine habits and circumstances that temporarily throw off your fluid balance.
Prolonged sitting or standing. When your calf muscles aren’t contracting, they can’t squeeze blood back toward your heart. Hours at a desk, a long flight, or a shift on your feet without movement lets fluid accumulate. This is the single most common reason otherwise healthy people notice puffy ankles at the end of the day.
High salt intake. Sodium causes your body to retain water. Research from the American Heart Association shows that excess sodium accumulates in skin tissue and creates concentration gradients that draw water into the surrounding area. Your kidneys also hold onto more fluid to dilute the extra sodium in your bloodstream, increasing overall fluid volume.
Heat. Warm temperatures cause blood vessels to widen, which lowers the pressure that normally keeps fluid inside your veins. Summer swelling in feet and ankles is common and typically resolves once you cool down and elevate your legs.
Alcohol. Drinking causes temporary vasodilation and can impair your kidneys’ ability to manage fluid balance, leading to noticeable puffiness the next day.
Swelling During Pregnancy
Mild foot and ankle swelling is normal during pregnancy, especially in the third trimester. Your blood volume increases by nearly 50%, your growing uterus puts pressure on the veins returning blood from your legs, and hormonal shifts make blood vessel walls more permeable. Most of this swelling is harmless and worst in the evening.
What’s not normal: sudden swelling that gets rapidly worse, swelling concentrated in your face or hands, or painful swelling in just one leg. Rapidly worsening swelling can signal that blood pressure is climbing outside a safe range, which may point to preeclampsia. Painful swelling in a single leg raises concern for a blood clot. Both require prompt evaluation.
Vein Problems and Valve Failure
Your leg veins contain one-way valves that keep blood moving upward toward the heart. Over time, these valves can weaken or stop closing properly. When that happens, blood flows backward and pools in the lower legs, a condition called chronic venous insufficiency. The increased pressure inside the veins forces fluid into surrounding tissue, producing persistent swelling that tends to worsen as the day goes on.
Venous insufficiency is more common after age 50, in people who’ve had blood clots, and in those with a family history of vein problems. Along with swelling, you might notice aching, skin discoloration around the ankles, or varicose veins. The condition is chronic but manageable with compression, movement, and sometimes medical procedures to close damaged veins.
Heart, Kidney, and Liver Conditions
When foot swelling is persistent and affects both legs, it sometimes points to a problem with a major organ.
Heart failure. When the heart can’t pump blood efficiently, blood backs up in the veins. That rising venous pressure forces fluid into surrounding tissues, particularly in the feet and ankles. This is one of the hallmark signs of congestive heart failure, and the swelling often gets worse throughout the day and improves overnight when you’re lying flat.
Kidney disease. Your kidneys regulate how much sodium and water stay in your body. When they’re damaged, they may retain too much of both. In nephrotic syndrome, the kidneys also leak large amounts of albumin (a protein that keeps fluid inside blood vessels) into the urine. When blood albumin drops low enough, fluid seeps out of vessels and into tissues throughout the body, with the feet and legs affected first.
Liver disease. Advanced liver disease reduces the production of albumin, creating the same protein imbalance. The liver also contributes to portal hypertension, which backs up fluid into the abdomen and lower extremities.
In all three cases, the swelling is typically bilateral (both feet), develops gradually, and comes with other symptoms like fatigue, shortness of breath, or changes in urination.
Medications That Cause Swelling
Several common medications list foot swelling as a side effect. Blood pressure drugs called calcium channel blockers are among the most frequent culprits. They work by relaxing blood vessels, but they relax the small arteries feeding your capillaries more than the veins draining them. This mismatch increases pressure inside the capillaries and pushes fluid into tissues. Newer versions of these drugs produce less swelling, but it remains a well-known side effect.
Other medications that can cause fluid retention include anti-inflammatory painkillers (like ibuprofen and naproxen), certain diabetes medications, corticosteroids, and some hormone therapies. If you notice new swelling after starting a medication, it’s worth bringing up at your next appointment. Stopping a medication on your own isn’t advisable, but alternatives with fewer fluid-related side effects often exist.
When Swelling in One Foot Is a Warning Sign
Swelling that appears in just one leg deserves closer attention. The most concerning cause is a deep vein thrombosis, a blood clot in one of the large veins of the leg. Along with swelling, DVT typically causes pain or cramping (often starting in the calf), warmth in the affected leg, and skin that turns red or purple.
A DVT is dangerous not because of the swelling itself but because the clot can break loose and travel to the lungs, causing a pulmonary embolism. Warning signs of that complication include sudden shortness of breath, chest pain that worsens when you breathe deeply, a rapid pulse, dizziness, or coughing up blood. This is a medical emergency.
Other causes of one-sided swelling include an injury, infection, or a lymphatic blockage, but DVT is the one that needs to be ruled out quickly.
Reducing Swelling at Home
For everyday, non-medical swelling, a few reliable strategies make a real difference.
Elevate your legs. Position your feet above the level of your heart for about 15 minutes, three to four times a day. This lets gravity work in your favor, draining pooled fluid back toward your core. Propping your legs on a couple of pillows while lying on the couch is usually enough height.
Move regularly. If you sit or stand for long stretches, take breaks every 30 to 60 minutes to walk around or do calf raises. Your calf muscles act as a pump for venous blood, and even brief contractions make a difference.
Cut back on sodium. Most people consume well above the recommended limit. Reducing processed foods, canned soups, and restaurant meals can meaningfully lower your fluid retention within days.
Try compression stockings. These apply graduated pressure to your lower legs, helping veins push blood upward. For mild, occasional swelling, stockings rated at 15 to 20 mmHg provide light support and are available without a prescription. For moderate swelling or diagnosed venous insufficiency, 20 to 30 mmHg is the most commonly prescribed daytime level. Stockings rated at 30 to 40 mmHg are reserved for more significant lymphedema or cases that don’t respond to lighter compression. Put them on in the morning before swelling starts for the best results.
Stay hydrated. It sounds counterintuitive, but drinking enough water helps your kidneys flush excess sodium rather than holding onto it. Dehydration actually encourages your body to retain more fluid.