Swollen ankles usually mean fluid has accumulated in the tissues around your ankle joint, a condition called edema. The causes range from something as simple as sitting too long or eating salty food to serious conditions involving your heart, kidneys, or liver. Whether one ankle is swollen or both, and whether the swelling appeared suddenly or built up over weeks, tells you a lot about what’s going on.
How Fluid Ends Up in Your Ankles
Your body constantly moves fluid between your bloodstream and the tissues around it. Tiny blood vessels called capillaries let water seep out to nourish cells, and your lymphatic system drains that fluid back into circulation. Swelling happens when more fluid leaks out of capillaries than your lymphatic system can absorb. Gravity pulls that excess fluid downward, which is why ankles and feet are the first place most people notice it.
Several things can tip this balance. Increased pressure inside your veins pushes more fluid out. Low protein levels in your blood reduce the pulling force that keeps fluid inside vessels. Damaged or blocked lymphatic channels can’t drain fluid fast enough. Inflammation from injury or infection makes capillary walls leakier. The underlying cause determines whether your swelling is harmless or a sign of something that needs attention.
One Swollen Ankle vs. Both
This distinction matters. Swelling in just one leg points toward a local problem, while both ankles swelling together usually signals something systemic affecting your whole body.
When only one ankle swells suddenly, about 40% of cases (after a blood clot is ruled out) turn out to be a muscle strain, tear, or twisting injury. Other causes of one-sided swelling include infection, a cyst behind the knee that has ruptured, or lymphatic blockage. The most urgent concern with sudden one-sided swelling is a deep vein thrombosis, or blood clot, which needs to be evaluated quickly.
When both ankles swell at the same time, the most common causes are heart failure, medications, kidney problems, or chronic vein disease. Acute worsening of heart failure is one of the most frequent reasons for sudden bilateral swelling.
Blood Clots: The Concern With Sudden Swelling
A deep vein thrombosis (DVT) forms when blood clots in one of the deep veins of your leg, blocking normal drainage and causing the leg to swell. The swelling typically affects one leg, not both. You may also notice warmth, redness, tenderness along the inner thigh or calf, and the calf of the affected leg may be noticeably larger than the other side.
Doctors evaluate DVT risk by looking at factors like recent surgery, prolonged bed rest, active cancer, paralysis, and whether the entire leg is swollen rather than just the ankle. Even among patients initially classified as low risk, about 12% turned out to have a clot on ultrasound in one primary care study. DVT is dangerous because a clot can break loose and travel to the lungs, so sudden one-sided leg swelling with pain or warmth warrants prompt medical evaluation.
Chronic Venous Insufficiency
This is the most common cause of persistent swelling in one or both legs over time. The valves inside your leg veins are supposed to keep blood flowing upward toward your heart. When those valves weaken or fail, blood pools in your lower legs, and the increased pressure pushes fluid into surrounding tissues.
Chronic venous insufficiency (CVI) is extremely common. More than 25 million adults in the United States have varicose veins, and over 6 million have more advanced vein disease. Prevalence rises with age: roughly 21% of men and 12% of women over 50 show signs of CVI on ultrasound. Over time, the constant fluid buildup and pressure cause visible changes to the skin around your ankles, including brownish discoloration from iron deposits, thickened or hardened skin, and in severe cases, open sores. About 20% of people with CVI eventually develop venous ulcers.
Heart, Kidney, and Liver Problems
When your heart can’t pump blood efficiently, blood backs up in the veins of your legs, forcing fluid into the tissues around your ankles and feet. Heart failure-related swelling often worsens throughout the day and improves overnight. You may also notice shortness of breath, especially when lying flat, and swelling in the abdomen.
Kidney disease causes swelling because your kidneys lose the ability to filter excess fluid and salt from your blood. This type of edema often shows up in the legs and around the eyes. In a condition called nephrotic syndrome, the kidneys leak protein into your urine, which lowers protein levels in your blood and reduces the force that normally keeps fluid inside your vessels.
Liver damage from cirrhosis disrupts protein production and increases pressure in the veins that drain the abdomen. This leads to fluid buildup in the belly first, then in the legs. Yellowing of the skin or eyes alongside ankle swelling can point toward liver involvement.
Medications That Cause Swollen Ankles
Several widely prescribed drugs cause ankle swelling as a side effect, and this is worth checking before assuming something more serious is going on.
- Blood pressure medications (calcium channel blockers): About 25% of people taking these develop ankle swelling. The incidence ranges from 5% to 60% depending on the specific drug and dose, and can reach 80% in patients on high doses for extended periods. High-dose regimens nearly triple the risk compared to lower doses.
- Pain relievers (NSAIDs): Common over-the-counter anti-inflammatory drugs like ibuprofen and naproxen cause noticeable edema in 3% to 5% of users. They reduce your kidneys’ ability to excrete sodium and water by about 30%.
- Nerve pain medications (gabapentin, pregabalin): These cause edema in 5% to 8% of users, with higher doses carrying greater risk.
- Steroids: Edema affects roughly 20% of people taking corticosteroids, particularly with long-term use.
- Hormonal medications: Oral contraceptives cause fluid retention in about 5% of users, typically after more than two years of use.
If your ankle swelling started around the same time as a new medication or a dose increase, that connection is worth discussing with whoever prescribed it. In many cases, switching to a different drug in the same class or adjusting the dose resolves the problem.
Pregnancy and Preeclampsia
Mild ankle swelling during pregnancy is normal, especially in the third trimester, as your body retains extra fluid and your growing uterus puts pressure on the veins draining your legs. But sudden or severe swelling, particularly in the face and hands along with the ankles, can signal preeclampsia.
Preeclampsia involves high blood pressure (above 140/90) and kidney damage that causes protein to spill into your urine. Beyond swelling, warning signs include severe headaches that won’t go away, blurred vision or dark spots in your vision, sharp pain in the upper right abdomen, and shortness of breath. Preeclampsia can progress to seizures and is a medical emergency requiring immediate hospital evaluation.
Red Flags That Need Prompt Attention
Most ankle swelling isn’t an emergency, but certain combinations of symptoms indicate you should be evaluated soon. Swelling in one leg with pain, warmth, or redness could be a blood clot. Swelling alongside shortness of breath or difficulty breathing may indicate heart failure or a clot that has traveled to your lungs. Swelling with a fever suggests infection. And swelling paired with yellowing skin or eyes points toward liver or kidney problems that need workup.
Sudden, unexplained swelling that appears in multiple body parts at once, or swelling that escalates rapidly over hours, warrants same-day evaluation. Swelling around the face or mouth after exposure to a new food, medication, or insect sting is a sign of a severe allergic reaction and requires emergency care.
Managing Everyday Ankle Swelling
For mild swelling related to prolonged sitting or standing, gravity is working against you, so use it in your favor. Elevating your legs above the level of your heart helps fluid drain back into circulation. Even 15 to 20 minutes a few times a day makes a difference. Avoid sitting or standing in one position for hours. Walking activates the calf muscles that pump blood upward through your veins.
Reducing sodium intake helps your body retain less fluid. For people with heart failure, guidelines recommend limiting sodium to 2,000 mg per day, and for moderate to severe cases, staying below that threshold. Even without heart failure, cutting back on processed foods and restaurant meals (which account for most sodium in the average diet) can noticeably reduce swelling.
Compression stockings apply graduated pressure to your legs, squeezing tightest at the ankle and gradually loosening toward the knee. For general swelling and varicose veins, stockings in the 20 to 30 mmHg range are the standard recommendation. People with swelling related to a prior blood clot typically need firmer compression in the 30 to 40 mmHg range. Knee-high stockings are sufficient for most people. Put them on in the morning before swelling builds up during the day, and remove them at night.
These measures help manage symptoms, but they don’t replace figuring out the underlying cause. Swelling that persists for more than a few days, keeps getting worse, or comes with any of the red flags above is your body telling you something needs investigation.