Swollen ankles and feet usually result from fluid collecting in the tissues of your lower legs, a condition called peripheral edema. Gravity naturally pulls fluid downward throughout the day, and when your body has trouble moving that fluid back up toward your heart, your ankles and feet pay the price. The causes range from harmless (sitting too long on a flight) to serious (heart or kidney disease), so the pattern and timing of your swelling matters.
The Most Common Everyday Causes
For many people, swollen ankles come down to lifestyle factors rather than a medical condition. Sitting or standing in one position for hours, especially during long flights or desk-bound workdays, allows fluid to pool in your lower legs. Your calf muscles act as a pump that pushes blood back up toward your heart, and when they’re inactive, that pump stalls.
High sodium intake is another frequent culprit. When you eat more salt than your body needs, your kidneys hold onto extra water to keep sodium levels balanced in your blood. That extra fluid has to go somewhere, and your ankles and feet are where it tends to settle. The American Heart Association recommends staying under 2,000 mg of sodium per day if you’re dealing with fluid retention, though many Americans consume well above that.
Heat also plays a role. In warm weather, your blood vessels dilate to release body heat, and some fluid leaks into surrounding tissue. This is why your shoes might feel tight on a hot summer afternoon even though nothing else has changed.
Medications That Cause Swelling
Several common prescription drugs cause ankle and foot swelling as a side effect. Blood pressure medications called calcium channel blockers (amlodipine and nifedipine are two widely prescribed ones) are among the most frequent offenders. They work by relaxing blood vessels, but they relax the vessels leading into your tissues more than the ones leading out. This creates a pressure imbalance that pushes fluid into surrounding tissue.
Diabetes medications in the thiazolidinedione class (pioglitazone, for example) cause the body to retain sodium and fluids. Certain pain medications, hormone therapies including estrogen, some antidepressants, and steroids can also trigger noticeable swelling. If your ankles started puffing up shortly after beginning a new medication, that timing is worth mentioning to your prescriber. Stopping or switching the drug often resolves the swelling, but don’t make changes on your own.
Venous Insufficiency
Your leg veins contain one-way valves that keep blood flowing upward against gravity toward your heart. When those valves weaken or become damaged, blood flows backward and pools in your lower legs. This is chronic venous insufficiency, and it’s one of the most common medical causes of persistent ankle swelling, particularly in people over 50.
The swelling from venous insufficiency tends to worsen throughout the day and improve overnight when you’re lying flat. Over time, you may notice skin changes on your lower legs: darkening, thickening, or a leathery texture. Some people develop varicose veins alongside the swelling. The condition is progressive, meaning it typically gets worse without treatment, but compression stockings and regular movement can slow it down significantly.
Heart, Kidney, and Liver Conditions
When your heart can’t pump blood efficiently, as happens in congestive heart failure, blood backs up in your veins. That backup increases pressure in the blood vessels of your legs, forcing fluid out into surrounding tissue. Heart-related swelling typically affects both legs equally and may come with shortness of breath, fatigue, or a feeling of tightness in your chest when lying down.
Kidney disease causes swelling through a different mechanism. Your kidneys filter waste and excess fluid from your blood. When they’re not working properly, sodium and water accumulate. The swelling can appear in your ankles and feet but also around your eyes, especially in the morning.
Liver cirrhosis reduces your body’s production of a blood protein called albumin, which helps keep fluid inside your blood vessels. With less albumin, fluid leaks out into tissues more easily. Cirrhosis-related swelling often shows up in the abdomen as well as the lower legs.
Blood Clots: A One-Leg Warning Sign
Deep vein thrombosis, or DVT, happens when a blood clot forms in one of the deep veins of your leg. The key distinguishing feature is that DVT almost always affects one leg, not both. If only one ankle or calf is swollen, especially if it’s also warm to the touch, painful, or has changed color (reddish or purplish), that pattern strongly suggests a clot rather than a systemic cause like heart or kidney problems.
DVT can occur without obvious symptoms, but when symptoms are present, they typically include cramping or soreness that starts in the calf and swelling that comes on relatively quickly. A clot becomes dangerous if it breaks loose and travels to your lungs, causing a pulmonary embolism. Sudden swelling in one leg paired with calf pain warrants same-day medical evaluation, especially after surgery, long travel, or a period of immobility.
Swelling During Pregnancy
Some degree of foot and ankle swelling is normal during pregnancy, particularly in the third trimester. Your blood volume increases by nearly 50%, and the growing uterus puts pressure on the veins returning blood from your legs. Ankle swelling that comes and goes, worsens with standing, and improves with rest is usually nothing to worry about.
The concern is preeclampsia, a pregnancy complication involving high blood pressure and organ stress. Preeclampsia-related swelling tends to appear in the hands, arms, or face rather than just the ankles. Sudden puffiness in your hands or around your eyes, rapid weight gain over a few days, persistent headaches, or vision changes are the warning signs that set preeclampsia apart from normal pregnancy swelling. Blood pressure readings of 140/90 or higher, combined with protein in the urine, are the diagnostic markers your provider will check.
How to Check the Severity
You can get a rough sense of how significant your swelling is with a simple press test. Push your thumb firmly into the swollen area for about five seconds, then release. If an indentation stays behind, that’s called pitting edema, and the depth and recovery time indicate severity.
- Grade 1: A shallow 2 mm pit that rebounds immediately. Mild.
- Grade 2: A 3 to 4 mm pit that fills back in within 15 seconds.
- Grade 3: A 5 to 6 mm pit that takes 15 to 60 seconds to rebound.
- Grade 4: An 8 mm pit that takes two to three minutes to fill back in. This indicates significant fluid retention.
Grade 1 or 2 with an obvious trigger (a long day on your feet, a salty meal, hot weather) is common and often manageable at home. Grade 3 or 4, or any pitting edema that persists daily without clear explanation, points toward a medical cause worth investigating.
Practical Ways to Reduce Swelling
Elevating your legs is the simplest and most effective immediate remedy. Position your legs above the level of your heart, ideally by lying back and propping your feet on pillows or a cushion against a wall. Aim for about 15 minutes, three to four times a day. This uses gravity to your advantage, helping fluid drain back toward your core.
Compression stockings apply graduated pressure to your lower legs, squeezing fluid upward. Low-compression stockings (under 20 mmHg) are available over the counter and work well for mild, activity-related swelling. Stockings rated 20 mmHg or higher require a prescription and are used for venous insufficiency or more persistent edema. Put them on first thing in the morning before swelling builds up during the day.
Movement matters more than most people realize. Even short walks or calf raises at your desk activate the muscle pump in your lower legs. If you’re on a long flight or stuck at a desk, flexing and pointing your feet every 20 to 30 minutes can make a noticeable difference. Cutting back on sodium, staying hydrated (which actually helps your kidneys release excess fluid rather than hoard it), and avoiding long periods of standing or sitting round out the basics.
When Swelling Signals an Emergency
Most ankle swelling develops gradually and isn’t dangerous on its own. But certain combinations of symptoms need immediate medical attention: shortness of breath alongside swollen legs (suggesting heart failure or a pulmonary embolism), sudden pain with swelling in one leg (possible blood clot), a swollen area that becomes hot and painful to touch, swelling that’s visibly spreading up your leg, or rapid weight gain over just a few days. These patterns indicate fluid shifts your body can’t manage safely on its own, and they require urgent evaluation rather than a wait-and-see approach.