Swollen ankles and feet usually mean fluid is building up in the tissues of your lower legs, a condition called edema. In most cases, it’s caused by something temporary like standing for long hours, eating salty food, or sitting through a long flight. But persistent or sudden swelling can signal an underlying health problem with your heart, kidneys, liver, or veins that needs attention.
Why Fluid Pools in Your Lower Legs
Your body constantly moves fluid between your bloodstream and the surrounding tissues. Tiny blood vessels called capillaries filter a small amount of fluid outward, and most of it gets reabsorbed or drained away by the lymphatic system. When this balance tips, meaning more fluid leaks out than your body can clear, the excess collects in your tissues. Gravity pulls that fluid downward, which is why the ankles and feet swell first.
Four basic things can throw off this balance: increased pressure inside the veins (from standing, heart failure, or a blocked vein), low protein levels in the blood (which normally help pull fluid back into vessels), leaky or damaged capillaries (from injury or inflammation), and a blocked lymphatic system that can’t drain the excess. Most causes of ankle swelling involve one or more of these mechanisms.
Common Causes That Aren’t Emergencies
Prolonged sitting or standing is the most frequent trigger. When your calf muscles aren’t contracting, they aren’t pumping blood back up toward your heart, so fluid settles. Long flights, desk jobs, and road trips are classic culprits. Hot weather also plays a role because heat causes blood vessels to widen, which lets more fluid seep into tissues.
High sodium intake is another common contributor. When you eat more salt than your kidneys can quickly filter, your body holds onto extra water to keep sodium levels balanced. That extra water often shows up as puffiness in the feet and ankles. The American Heart Association recommends staying under 1,500 mg of sodium per day for general health, but the average intake is well above that.
Pregnancy causes swelling in most women, particularly in the third trimester, because of increased blood volume and pressure from the growing uterus on pelvic veins. Mild, gradual swelling in both feet is normal. However, sudden swelling, especially in the face and hands, can be a warning sign of preeclampsia, a serious blood pressure condition that develops during pregnancy and requires immediate medical evaluation.
Medical Conditions Behind Chronic Swelling
Chronic Venous Insufficiency
This is one of the most common medical causes of persistent ankle swelling. Veins in your legs have one-way valves that keep blood flowing upward toward your heart. When those valves weaken or fail, blood pools in the lower legs. Over time, the increased pressure forces fluid into the surrounding tissue. You may also notice skin discoloration around the ankles, a heavy or achy feeling in your legs, or visible varicose veins. The condition is more common with age, obesity, and a history of blood clots.
Heart Failure
When the heart can’t pump blood efficiently, pressure builds in the veins leading back to the heart. That backup pushes fluid out of the capillaries and into the tissues, particularly in the legs, ankles, and feet. Swelling from heart failure tends to worsen throughout the day and may be accompanied by shortness of breath, fatigue, or difficulty lying flat at night. Swelling in the abdomen can also develop.
Kidney Disease
Your kidneys regulate how much fluid and salt stay in your bloodstream. When kidney function declines, excess fluid and sodium build up, causing swelling in the legs and sometimes around the eyes. The swelling is often more noticeable in the morning.
Liver Cirrhosis
Severe liver damage disrupts the production of albumin, a protein that helps keep fluid inside blood vessels. Low albumin levels let fluid leak into surrounding tissues. Cirrhosis also causes fluid to accumulate in the abdomen (a condition called ascites), alongside swelling in the legs.
Medications That Cause Swelling
Several common medications list ankle swelling as a side effect. Blood pressure drugs known as calcium channel blockers are among the most frequent offenders. The swelling is dose-related: at lower doses, it affects roughly 1 to 15% of patients, but at high doses taken long-term, the incidence can exceed 80%. The swelling happens because these drugs relax blood vessel walls, which increases fluid leakage into tissues.
Other medications that can cause fluid retention include certain diabetes drugs, steroids, hormonal therapies like estrogen or testosterone, and some anti-inflammatory painkillers. If you notice new swelling after starting a medication, it’s worth bringing up with the prescriber. Stopping or switching the drug often resolves the problem.
One Leg vs. Both Legs Matters
Swelling in both ankles usually points to a systemic cause: something affecting your whole body like heart failure, kidney problems, medication side effects, or simply too much salt. It tends to develop gradually and look similar on both sides.
Swelling in just one leg is a different situation. A blood clot in a deep leg vein, known as DVT, is one of the more serious possibilities. The affected leg may be warm, red, tender, or noticeably larger than the other. DVT is a medical emergency because a clot can break free and travel to the lungs. Risk factors include recent surgery, long periods of immobility, cancer, and hormonal birth control. If one leg swells suddenly and is painful or warm, get it evaluated the same day. Diagnosis typically involves an ultrasound of the leg veins.
Other causes of one-sided swelling include an injury, infection, or a localized vein problem. A past DVT can also damage vein valves permanently, causing chronic swelling on that side.
How Doctors Assess Swelling
One simple test involves pressing a finger into the swollen area for a few seconds and then releasing. If an indentation remains, it’s called pitting edema, and the depth and rebound time indicate severity. Grade 1 leaves a shallow 2 mm pit that rebounds immediately. Grade 2 creates a 3 to 4 mm pit that fills back in within 15 seconds. Grade 3 produces a 5 to 6 mm pit that takes up to a minute to rebound. Grade 4, the most severe, leaves an 8 mm pit that persists for two to three minutes.
Beyond the physical exam, blood tests can check kidney and liver function, protein levels, and markers of heart failure. An ultrasound may be used to evaluate blood flow in the veins or to check heart function, depending on the suspected cause.
Reducing Swelling at Home
Elevation is the simplest and most effective immediate remedy. Lie down and prop your legs above heart level on pillows for about 15 minutes, three to four times a day. This lets gravity help drain fluid back toward your core. Even during long sitting periods, propping your feet up on a stool helps.
Reducing sodium makes a meaningful difference for many people. Aiming for under 2,000 mg per day is a practical target, which means reading labels and cutting back on processed foods, restaurant meals, and canned soups. Regular movement matters too. Walking, calf raises, and ankle circles all activate the muscle pump in your lower legs that pushes blood and fluid upward.
Compression stockings apply graduated pressure to your legs, tightest at the ankle and loosening toward the knee, to help prevent fluid from pooling. Mild support stockings (15 to 20 mmHg) work well for occasional swelling from travel or long days on your feet. Moderate compression (20 to 30 mmHg) is the most commonly prescribed level for chronic venous insufficiency or persistent mild edema. Firmer levels of 30 to 40 mmHg are reserved for more severe cases and should be fitted with professional guidance.
Signs That Need Prompt Attention
Most ankle swelling is harmless, but certain patterns warrant a call or visit to your doctor sooner rather than later. Swelling that comes on suddenly in one leg, especially with pain, warmth, or redness, raises concern for a blood clot. Swelling paired with shortness of breath could indicate a heart or lung problem. During pregnancy, sudden puffiness in the face and hands alongside headaches or vision changes are red flags for preeclampsia. And swelling that doesn’t improve with elevation and sodium reduction, or that gets progressively worse over weeks, suggests an underlying condition that needs diagnosis.
Persistent swelling that goes unaddressed can lead to skin changes over time, including thickening, discoloration, and eventually breakdown or ulcers around the ankles. Addressing the root cause early prevents these complications.