Feet swell when fluid leaks out of tiny blood vessels and gets trapped in the surrounding tissue faster than your body can drain it away. This is called edema, and it happens to nearly everyone at some point. The causes range from something as simple as sitting too long to something as serious as heart or kidney disease, so understanding the pattern of your swelling matters.
Your body constantly balances fluid pressure inside and outside your blood vessels. When that balance tips, whether from gravity, inflammation, organ problems, or medication, fluid pools in the lowest point it can find: your feet and ankles.
How Fluid Ends Up Trapped in Your Feet
Blood vessels aren’t sealed pipes. They have tiny gaps that let fluid move in and out, delivering nutrients to tissues and carrying waste back into the bloodstream. Two opposing forces keep this exchange in check: the pressure of blood pushing fluid out through vessel walls, and the pull of proteins inside vessels drawing fluid back in. When outward pressure rises or inward pull weakens, more fluid escapes into the tissue than returns. If the excess overwhelms your lymphatic system (a network of tiny drainage channels), the fluid accumulates and your feet visibly swell.
Gravity plays a major role. Your feet sit at the bottom of your circulatory system, so any extra fluid naturally settles there. That’s why swelling tends to worsen throughout the day and improve overnight when you’re lying flat.
Sitting or Standing Too Long
The most common reason for occasional foot swelling is simply staying in one position for hours. When you sit at a desk, ride in a car, or stand behind a counter all day, the muscles in your calves don’t contract enough to push blood back up toward your heart. Blood pools in your lower legs, pressure builds in the small vessels, and fluid seeps into the tissue around your feet and ankles.
This type of swelling is usually mild, affects both feet equally, and goes down after you move around or elevate your legs. Taking short walks every 30 to 60 minutes, flexing your ankles while seated, and propping your feet up at the end of the day are typically enough to prevent it.
Heart, Kidney, and Liver Problems
When swelling in both feet becomes persistent or gets worse over weeks, it can signal that a major organ isn’t working properly.
In heart failure, the heart can’t pump blood efficiently enough. Blood backs up in the veins, raising the pressure inside vessels and forcing more fluid into the tissues. At the same time, reduced blood flow to the kidneys triggers them to retain even more fluid in an attempt to boost circulation, which only compounds the problem. The result is progressive swelling that may start in the ankles and creep up the legs.
Kidney disease causes swelling through a different path. Damaged kidneys can’t filter excess fluid and sodium out of the blood efficiently, so fluid volume rises throughout the body. They may also leak protein into the urine, reducing the concentration of protein in the blood. Since blood proteins are what pull fluid back into vessels, losing them means fluid stays trapped in the tissue.
Liver disease, particularly cirrhosis, reduces the liver’s ability to produce those same blood proteins. Low protein levels in the blood weaken the pull that keeps fluid inside vessels, leading to swelling in the legs and often the abdomen as well.
Chronic Venous Insufficiency
Your leg veins contain one-way valves that keep blood moving upward toward the heart. When those valves weaken or fail, gravity pulls blood backward and it pools in the lower legs. This condition, called chronic venous insufficiency, is one of the most common causes of persistent foot and ankle swelling, especially in people over 50.
The hallmark is swelling that worsens after standing or sitting for a while and improves overnight. Over time, the high pressure in the veins can burst tiny capillaries near the skin surface, causing brownish discoloration around the ankles, visible varicose veins, and in severe cases, open sores on the lower legs that are slow to heal. If your swelling follows this pattern, compression stockings and regular movement are the first line of management.
Medications That Cause Swelling
Several common medications cause foot swelling as a side effect. The most well-known culprits are calcium channel blockers, a class of blood pressure drugs that includes amlodipine, nifedipine, and felodipine. These medications widen blood vessels, which lowers blood pressure but also lets more fluid leak from capillaries into surrounding tissue. Ankle swelling affects anywhere from 1% to 15% of people taking these drugs at standard doses, and the rate can exceed 80% at higher doses over time.
One important detail: this type of swelling doesn’t respond well to water pills (diuretics). That’s because the fluid isn’t being retained by the kidneys. It’s being redistributed from inside the blood vessels to the tissue outside them. If you suspect your blood pressure medication is causing swelling, talk to your prescriber about adjusting the dose or switching to a different type.
Other medications that commonly cause foot swelling include anti-inflammatory painkillers like ibuprofen and naproxen, certain diabetes drugs, steroids like prednisone, and some antidepressants. Hormone therapies, including estrogen-containing birth control, can also contribute.
Salt Intake and Diet
Sodium makes your body hold onto water. When you eat a high-sodium meal, your kidneys temporarily retain more fluid to keep sodium concentrations balanced in the blood. That extra fluid has to go somewhere, and it often ends up in your feet.
For people already prone to swelling from heart failure or kidney issues, sodium restriction makes a meaningful difference. The Heart Failure Society of America recommends limiting sodium to 2,000 to 3,000 milligrams per day, with a stricter limit of under 2,000 milligrams for moderate to severe cases. For context, a single fast-food meal can easily contain 1,500 milligrams or more. Reading nutrition labels and cooking at home more often are the most practical ways to cut back.
Pregnancy-Related Swelling
Some degree of foot swelling is normal during pregnancy, especially in the third trimester. The growing uterus puts pressure on veins that return blood from the legs, and hormonal changes make blood vessels more permeable. Most pregnant people notice mild swelling that comes and goes.
What’s not normal is sudden, severe swelling, particularly in the face and hands. This can be an early sign of preeclampsia, a serious pregnancy complication involving high blood pressure. Other warning signs include severe headaches, vision changes like blurriness or light sensitivity, pain under the ribs on the right side, shortness of breath, and nausea or vomiting. Preeclampsia requires prompt medical attention because it can progress quickly and affect both the mother and baby.
One Foot vs. Both Feet
The pattern of swelling tells you a lot about its cause. Swelling in both feet that develops gradually usually points to a systemic issue: heart, kidney, or liver problems, medication side effects, venous insufficiency, or simply too much time on your feet.
Sudden swelling in just one foot or leg is a different situation entirely. It may indicate a deep vein thrombosis (a blood clot in a deep leg vein), especially if it comes with pain, warmth, or redness in the affected leg. Blood clots can be dangerous if a piece breaks off and travels to the lungs, so one-sided swelling that appears quickly warrants urgent evaluation. Other causes of one-sided swelling include injury, infection, and lymphatic blockage.
What You Can Do at Home
For mild, occasional swelling, a few simple strategies make a noticeable difference. Elevating your feet above heart level for 15 to 20 minutes helps fluid drain back toward your core. Breaking up long periods of sitting or standing with short walks keeps your calf muscles pumping blood upward. Reducing sodium in your diet lowers the amount of fluid your body retains.
Compression socks apply graduated pressure that supports your veins and prevents fluid from pooling. For mild swelling, socks rated at 15 to 20 mmHg are a good starting point and are available without a prescription. People with chronic venous insufficiency or more significant swelling often need 20 to 30 mmHg or higher, which your provider can help determine. Compression levels of 30 to 40 mmHg and above are typically reserved for diagnosed conditions like lymphedema or severe venous disease and should be fitted based on clinical assessment.
If your swelling is new, persistent, worsening, or accompanied by shortness of breath, chest pain, or sudden one-sided leg swelling, those patterns point to causes that need medical evaluation rather than home management.