Swollen ankles usually mean fluid is building up in the tissues of your lower legs, a condition called peripheral edema. It can be as harmless as sitting too long on a flight or as serious as a sign that your heart, kidneys, or liver aren’t working properly. The cause matters, so understanding the pattern of your swelling, whether it affects one leg or both, and what other symptoms come with it can help you figure out what’s going on.
Why Fluid Pools in Your Ankles
Your body constantly moves fluid between your blood vessels and surrounding tissues. Blood pressure inside tiny capillaries pushes fluid out, while proteins in your blood (mainly albumin) pull fluid back in. Gravity adds another force: when you’re upright, blood naturally pools in the lowest points of your body. Your leg veins have one-way valves that push blood back toward the heart, and your lymphatic system drains excess fluid from tissues.
Ankle swelling happens when any part of this system falls out of balance. Higher pressure inside the veins, lower protein levels in the blood, damaged valves, a blocked lymphatic system, or simply standing all day can tip the scales toward too much fluid leaking out and not enough returning. Because your ankles sit at the bottom of the chain, they’re the first place fluid accumulates.
Common Causes of Swollen Ankles
Prolonged Sitting or Standing
This is the most frequent and least worrisome cause. Gravity pulls fluid downward, and without regular muscle contractions in your calves to pump blood back up, it collects around the ankles. Long flights, desk jobs, and road trips are classic triggers. The swelling is usually mild, affects both legs equally, and goes away once you move around or elevate your feet.
Chronic Venous Insufficiency
The valves inside your leg veins can weaken or fail over time, often after a previous blood clot or simply from years of wear. When these valves stop closing properly, blood flows backward and pools in the lower legs instead of returning to the heart. Perforator veins, which connect deep and superficial veins, can also lose valve function, allowing high-pressure blood to surge into the surface veins and stretch them further.
Early on, you’ll notice swelling that worsens through the day and improves overnight. Over months or years, the sustained pressure causes visible changes: brownish skin discoloration from iron deposits leaking out of red blood cells, a thickening and hardening of the skin and fat layer called lipodermatosclerosis, and eventually open sores (venous ulcers) near the ankle that heal slowly. The risk of skin infections also rises.
Heart Failure
When the heart can’t pump blood efficiently, blood backs up in the veins. That backup raises pressure inside the vessels and forces fluid into surrounding tissues. Swelling from heart failure typically affects both ankles and may extend up the shins. It often comes with other symptoms: shortness of breath during activity or when lying flat, fatigue, and rapid weight gain from fluid retention. If you press your finger into the swollen area and it leaves a visible dent that takes several seconds to fill back in, that’s called pitting edema, and it’s characteristic of heart-related swelling.
Kidney and Liver Disease
Your kidneys filter blood and regulate fluid balance. In conditions like nephrotic syndrome, the kidneys let large amounts of protein leak into the urine. With less protein in your blood, there’s less force pulling fluid back into the vessels, so it seeps into tissues and causes widespread swelling, often noticeable in the ankles, face, and around the eyes.
Liver disease, particularly cirrhosis, creates a similar problem. A damaged liver produces less albumin, the main blood protein responsible for keeping fluid inside your vessels. The result is the same: fluid leaks out and accumulates, often in the legs and abdomen.
Medications
Several common medications cause ankle swelling as a side effect. Calcium channel blockers (used for high blood pressure), certain diabetes medications, steroids, hormonal therapies including estrogen, and some antidepressants can all promote fluid retention. The swelling usually affects both legs, develops gradually after starting the medication, and resolves when the medication is changed.
Pregnancy
Mild ankle swelling is normal during pregnancy, especially in the third trimester, because the growing uterus puts pressure on pelvic veins and your body retains more fluid overall. However, sudden or severe swelling after 20 weeks of pregnancy can signal preeclampsia, a serious condition defined by blood pressure at or above 140/90 mm Hg and protein in the urine. Preeclampsia requires prompt medical attention.
One Leg vs. Both Legs
The pattern of swelling is one of the most useful clues to its cause. Swelling in both ankles usually points to a systemic issue: heart failure, kidney disease, liver problems, medication side effects, or simply too much time on your feet. Swelling in just one leg is more concerning for a local problem like a blood clot or an injury.
A deep vein thrombosis (DVT) is a blood clot that forms in a deep vein, most often in the calf or thigh. It typically causes swelling, pain, or cramping in one leg, along with warmth and skin that may look red or purple. A DVT 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 with deep breaths, a rapid pulse, dizziness, or coughing up blood. A pulmonary embolism is a medical emergency.
Lymphedema, where the lymphatic drainage system is damaged or blocked, can also affect one leg. In its early stages, the swelling pits when pressed. Over time, the tissue becomes firm and the skin thickens, and pressing no longer leaves an indent. This is common after cancer treatment that involves removing lymph nodes, but it can also occur on its own.
Pitting vs. Non-Pitting Edema
If you press your thumb into the swollen area for a few seconds and it leaves a dent, you have pitting edema. This type is associated with heart failure, DVT, venous insufficiency, and medication-related swelling. It happens because the leaked fluid is mostly water with relatively little protein.
Non-pitting edema, where the skin bounces back immediately, suggests different causes. Advanced lymphedema produces thick, firm swelling that doesn’t indent. Lipedema, a condition involving abnormal fat distribution in the legs, also causes non-pitting swelling and typically affects both legs symmetrically while sparing the feet. Severe hypothyroidism can cause a type of non-pitting swelling called myxedema, though this is uncommon.
Reducing Swelling at Home
For mild, everyday ankle swelling, a few strategies make a real difference. Elevating your legs above the level of your heart for about 15 minutes, three to four times a day, helps gravity drain fluid back toward the center of your body. If you spend long hours sitting, take brief walking breaks every 30 to 60 minutes to activate the calf muscles that pump blood upward.
Compression stockings apply steady pressure that supports your veins and prevents fluid from leaking into tissues. For mild swelling, stockings rated at 20 to 30 mmHg of pressure are typically sufficient. Moderate to severe edema or diagnosed venous insufficiency may call for 30 to 40 mmHg, and chronic venous insufficiency sometimes requires 40 to 50 mmHg. A healthcare provider can help you choose the right level.
Sodium plays a direct role in fluid retention. For people with heart failure and fluid overload, guidelines from the American Heart Association recommend limiting sodium to no more than 2,000 mg per day. Even without heart failure, cutting back on processed foods, restaurant meals, and added salt can noticeably reduce swelling for many people. The average American consumes over 3,400 mg of sodium daily, so there’s usually room to improve.
When Swollen Ankles Need Attention
Swelling that comes on suddenly in one leg, especially with pain, warmth, or skin color changes, warrants prompt evaluation to rule out a blood clot. Swelling in both legs that develops over days or weeks and doesn’t resolve with elevation could indicate a heart, kidney, or liver problem, particularly if you also notice shortness of breath, unexplained weight gain, or decreased urination.
During pregnancy, a rapid increase in swelling, headaches, vision changes, or upper abdominal pain alongside swollen ankles are warning signs of preeclampsia. And if ankle swelling appears shortly after starting a new medication, your prescriber can often switch to an alternative that doesn’t cause fluid retention.