Feet swell when fluid leaks out of tiny blood vessels and collects in the surrounding tissue. This can happen for reasons as simple as eating a salty meal or standing all day, or it can signal something more serious like heart failure or a blood clot. Understanding what’s behind the swelling helps you figure out whether it’s a minor nuisance or something worth investigating.
How Fluid Ends Up in Your Feet
Your body constantly moves fluid between your bloodstream and the tissue around it. Two forces keep this exchange balanced: pressure inside your blood vessels pushes fluid out, while proteins (mainly one called albumin) pull fluid back in. When something tips this balance, fluid escapes faster than it returns, and gravity pulls it down to your feet and ankles.
Once swelling starts, your kidneys can make things worse. They sense the shift in fluid and respond by holding onto more sodium and water, which increases blood volume and pushes even more fluid into your tissues. This feedback loop explains why swelling that starts small can gradually worsen over hours or days.
Common Everyday Causes
Most foot swelling is temporary and tied to daily habits. Sitting or standing in one position for long stretches, like during a flight or a desk job, lets gravity pool blood in your lower legs. Without the pumping action of walking, fluid slowly seeps into the tissue around your ankles and feet.
High sodium intake is another frequent trigger. When you eat a salt-heavy meal, your kidneys retain extra water to keep the sodium concentration in your blood balanced. That extra fluid increases the pressure inside your blood vessels, forcing more of it into surrounding tissues. The recommended daily sodium limit is 2,300 milligrams, roughly one teaspoon of table salt, though most people regularly exceed that.
Heat also plays a role. In warm weather, blood vessels near the skin’s surface widen to help you cool down. This dilation increases blood flow to the capillaries and allows more fluid to leak out, which is why your shoes may feel tighter on hot days.
Medications That Cause Swelling
Certain medications are surprisingly common culprits. Blood pressure drugs called calcium channel blockers are among the worst offenders. A large meta-analysis found that roughly 25% of people taking them develop peripheral edema, and the drugs were associated with an almost 11-fold increase in risk. The swelling happens because these medications widen the small arteries feeding your capillaries, increasing blood flow and fluid leakage.
Common pain relievers like ibuprofen and naproxen also contribute. They interfere with how your kidneys handle sodium, leading to increased blood volume and higher pressure in your vessels. Both non-selective versions and newer selective versions cause similar rates of swelling.
Diabetes medications in the thiazolidinedione class cause edema in about 3% to 5% of people when used alone, but the rate climbs to 13% to 16% when combined with insulin. Steroids, certain antidepressants, and some hormone therapies can trigger swelling too. If your feet started swelling around the time you began a new medication, that connection is worth raising with your prescriber.
Chronic Venous Insufficiency
Your leg veins contain one-way valves that push blood upward toward your heart and prevent it from flowing back down. When those valves weaken or the veins stretch too wide for the valve flaps to meet, blood pools in the lower legs. This is called chronic venous insufficiency, and it’s the single most common cause of persistent leg swelling.
The condition develops gradually. Early signs include varicose veins and mild ankle puffiness that improves overnight. Over time, the sustained high pressure in the veins can cause skin discoloration around the ankles, a leathery texture to the skin, and in advanced cases, open sores that are slow to heal. Diagnosis is straightforward: an ultrasound of the leg veins can confirm whether the valves are leaking. Risk factors include age, obesity, pregnancy, prolonged standing, and a family history of varicose veins.
Heart Failure
When the heart can’t pump blood efficiently, pressure builds up in the veins leading back to the heart. That elevated pressure pushes fluid out of the capillaries and into the tissue, starting with the feet and ankles because they’re the lowest point. At the same time, reduced blood flow to the kidneys triggers a hormonal cascade that tells the body to hold onto sodium and water, making the swelling progressively worse.
Heart failure-related swelling tends to affect both legs equally, worsens over the course of the day, and may improve somewhat after a night of sleep. It often comes alongside other symptoms: shortness of breath with exertion or when lying flat, fatigue, and rapid weight gain from fluid retention. Gaining several pounds over just a few days is a hallmark sign.
Kidney and Liver Disease
Your kidneys regulate how much sodium and water your body keeps. When kidney function declines, they lose the ability to flush excess fluid, and the resulting buildup shows up as swelling in the feet, ankles, and sometimes around the eyes. Advanced kidney disease also causes a drop in blood albumin levels. Since albumin is the protein responsible for pulling fluid back into the bloodstream, levels below 2 grams per deciliter often result in noticeable edema.
Liver disease, particularly cirrhosis, causes a similar drop in albumin because the liver is where albumin is made. Low production means less pulling force inside the blood vessels, so fluid escapes freely into surrounding tissue.
Lymphedema
Your lymphatic system acts as a drainage network, collecting excess fluid from tissues and returning it to your bloodstream. When this system is damaged or blocked, fluid accumulates in the affected area. Unlike other types of swelling, lymphedema characteristically affects the top of the foot and the toes, giving the foot a boxy, swollen appearance.
One distinguishing feature is the Stemmer sign: if you can’t pinch a fold of skin between the top of your foot and the base of your second toe, the skin has thickened in a way that’s characteristic of lymphedema. As the condition progresses, the skin may become rough and thickened, the toenails can develop a curved “ski jump” shape, and the swelling no longer goes away with elevation. Lymphedema can result from surgery (especially procedures that remove lymph nodes), radiation therapy, infection, or in some cases it develops without a clear cause.
Pregnancy-Related Swelling
Mild foot and ankle swelling is normal during pregnancy, especially in the third trimester. The growing uterus puts pressure on the veins returning blood from the legs, and hormonal changes cause the body to retain more fluid overall. This type of swelling typically develops gradually and affects both feet.
What’s not normal is sudden swelling, particularly in the face and hands, which can be a sign of preeclampsia. This condition is defined by high blood pressure and signs of organ damage, most often to the kidneys. Severe headaches, blurred vision, upper abdominal pain, or sudden shortness of breath alongside new swelling warrant immediate medical attention.
When One Foot Swells
The pattern of swelling matters. Swelling in both feet usually points to a systemic cause: heart, kidney, or liver problems, medication side effects, or venous insufficiency. Swelling in just one foot or leg, especially if it comes on suddenly, raises different concerns.
Acute one-sided swelling is most commonly caused by a deep vein thrombosis (DVT), a blood clot in the deep veins of the leg. Along with the swelling, the leg may feel warm, tender, and appear reddish. DVT requires urgent evaluation because the clot can break free and travel to the lungs. Onset within 72 hours, combined with warmth and tenderness, should prompt same-day medical assessment. Less commonly, one-sided swelling can result from an injury, infection, or, rarely, a tumor pressing on the veins or lymphatic vessels in the pelvis.
Reducing Swollen Feet at Home
For everyday swelling without a serious underlying cause, a few strategies reliably help. Elevating your legs above heart level allows gravity to work in your favor, draining fluid back toward your torso. Lying on the couch with your feet propped on two or three pillows works well. The longer you maintain this position, the more fluid drains, so aim for at least 20 to 30 minutes at a time.
Movement is equally important. Walking, even briefly, activates the calf muscles that act as pumps to push blood back up through your veins. If you’re stuck at a desk, flexing your ankles and pressing your feet against the floor every 30 minutes mimics some of that pumping action. Compression socks apply steady pressure that helps prevent fluid from pooling. They’re most effective when put on first thing in the morning, before swelling has a chance to develop.
Cutting back on sodium makes a measurable difference for people whose swelling is diet-related. Processed foods, restaurant meals, and canned soups are the biggest sources for most people. Staying well-hydrated sounds counterintuitive, but adequate water intake actually helps your kidneys flush sodium more efficiently rather than holding onto it.