Swollen ankles usually mean fluid is building up in the tissue around your lower legs, a condition called peripheral edema. Most of the time it’s harmless and temporary, caused by standing too long, eating salty food, or sitting through a long flight. But persistent or sudden swelling can also be a signal from your heart, kidneys, liver, or veins that something deeper needs attention. The key is knowing which patterns are routine and which ones warrant a closer look.
Why Fluid Pools in Your Ankles
Gravity pulls fluid downward throughout the day, and your ankles sit at the lowest point when you’re standing or sitting. Normally, your veins and lymph system push that fluid back up toward your heart. When something disrupts that return flow, or when your body holds onto more fluid than usual, the extra liquid seeps into the surrounding tissue and your ankles puff up.
You can test whether your swelling involves trapped fluid by pressing a finger firmly into the swollen area for a few seconds. If the indent stays visible after you release, that’s called pitting edema. Doctors grade it on a scale from 1 to 4: a shallow 2 mm dent that bounces back immediately is grade 1, while a deep 8 mm pit that takes two to three minutes to fill back in is grade 4. The deeper and slower the rebound, the more fluid is involved.
Common, Non-Serious Causes
The most frequent triggers are lifestyle-related. Sitting or standing in one position for hours, especially during travel, slows blood return from your legs. Hot weather causes blood vessels to expand, letting more fluid leak into tissue. A high-sodium meal can cause your body to retain water, and the effects often show up most noticeably at your ankles. These types of swelling tend to be mild, affect both legs equally, and resolve once you move around, elevate your feet, or reduce your salt intake.
One Ankle vs. Both Ankles
Whether the swelling is in one leg or both tells you a lot about what might be causing it. Swelling in both ankles at the same time usually points to a systemic issue: something affecting your whole body, like fluid retention, a medication side effect, or an organ problem. It’s the more common pattern and often less urgent.
Swelling in just one ankle is different. The most important thing to rule out is a deep vein thrombosis (DVT), a blood clot in the deep veins of your leg. A DVT typically causes swelling that comes on relatively quickly, often with warmth, redness, or pain in the calf. This matters because a clot can break free and travel to the lungs, causing a pulmonary embolism. Seek immediate medical attention if you have sudden swelling in one leg along with shortness of breath, chest pain (especially when breathing in deeply), a rapid heartbeat, or lightheadedness.
Other causes of one-sided swelling include infection, injury, or lymphedema, which is a buildup of lymph fluid that sometimes develops after surgery or radiation therapy involving the lymph nodes in the pelvis or groin.
Organ-Related Causes
When ankle swelling sticks around or worsens over weeks, it can reflect a problem with one of the major organs that regulate fluid balance in your body.
Heart failure is one of the most well-known causes. When the heart’s pumping power weakens, blood backs up in the veins returning from the legs. Fluid gets pushed out into the surrounding tissue, and you’ll notice your ankles, feet, and sometimes your entire lower legs swelling, particularly by the end of the day. You might also feel short of breath when lying flat or notice unusual fatigue.
Kidney disease impairs your body’s ability to filter excess fluid and salt from the blood. The swelling tends to show up in the legs and also around the eyes. In more advanced kidney damage, protein leaks out of the blood through the damaged filters, which lowers protein levels in the bloodstream. Since blood proteins help hold fluid inside your vessels, losing them causes even more fluid to seep into tissue.
Liver disease, particularly cirrhosis, disrupts protein production and increases pressure in the veins draining the abdomen. This can cause fluid buildup both in the belly and in the legs.
Medications That Cause Swelling
Several common medications list ankle swelling as a side effect, and it’s worth checking your prescriptions if the timing lines up. Calcium channel blockers, a widely prescribed class of blood pressure medication, are among the most frequent culprits. Swelling occurs in 1 to 15% of people taking standard doses, but that number can climb above 80% in people on high doses over the long term. Adding a second blood pressure medication can reduce the problem significantly. In one clinical trial, patients taking a calcium channel blocker combined with another drug had a swelling rate of about 8%, compared to nearly 19% in those on the calcium channel blocker alone.
Anti-inflammatory painkillers, certain diabetes medications, steroids, and some hormone therapies can also cause your body to retain fluid. If you suspect a medication is behind your swollen ankles, talk to your prescriber before making changes. There are often alternatives or combination strategies that reduce the problem.
Vein Problems and Chronic Swelling
Chronic venous insufficiency (CVI) is one of the most common causes of long-lasting ankle swelling, and it gets more common with age. The veins in your legs contain one-way valves that keep blood moving upward toward the heart. When those valves weaken or get damaged, blood flows backward and pools in the lower legs. This backward flow increases pressure inside the veins, forcing fluid out into surrounding tissue.
Valve damage often follows a previous blood clot. Even after a DVT resolves, the clot can leave behind scarred, malfunctioning valves in the deep veins. Varicose veins, which affect between 5 and 30% of adults, are a visible sign of valve problems in the surface veins. A large international study found that clinically significant vein disease affects roughly 60% of the population to some degree. CVI becomes noticeably more common after age 50, affecting about 21% of men and 12% of women in that age group. In its most severe form, CVI leads to skin changes and ulcers on the lower legs, which affect about 1% of adults.
Swollen Ankles During Pregnancy
Mild ankle swelling is extremely common in pregnancy, especially in the third trimester. The growing uterus presses on the veins returning blood from the legs, and hormonal changes cause the body to retain more fluid. This type of swelling is usually harmless.
What’s not normal is sudden, severe swelling, particularly in the hands and face, combined with high blood pressure. This pattern can signal preeclampsia, a serious pregnancy complication that typically develops after 20 weeks. Preeclampsia is defined by new-onset high blood pressure (140/90 or higher) alongside either protein in the urine or signs of organ stress. Severe cases involve blood pressure at or above 160/110. Swelling alone doesn’t mean preeclampsia, but rapid swelling paired with headaches, vision changes, or upper abdominal pain needs immediate evaluation.
What You Can Do at Home
For mild, occasional swelling, simple strategies make a real difference. Elevating your legs above heart level for 20 to 30 minutes helps fluid drain back toward your core. Moving regularly, even just flexing your feet or taking a short walk, activates the calf muscles that act as pumps for your veins. Reducing sodium intake cuts down on fluid retention.
Compression stockings provide graduated pressure that supports your veins and prevents fluid from pooling. They come in different strengths: 15 to 20 mmHg offers light support for tired, mildly swollen legs. A 20 to 30 mmHg level is better for mild edema. For moderate to severe swelling or lymphedema, 30 to 40 mmHg stockings provide stronger compression, though at this level it’s worth getting a proper fit and confirming the cause of swelling first.
Signs That Need Medical Attention
Ankle swelling that’s new, persistent, or worsening over days to weeks deserves a medical evaluation, especially if it’s accompanied by shortness of breath, chest tightness, or reduced urine output. Swelling in one leg that appears suddenly, with pain or warmth, needs prompt assessment to rule out a blood clot. If you press on the swelling and it leaves a deep pit that’s slow to rebound, that suggests a significant amount of fluid buildup. And any swelling paired with skin changes like darkening, hardening, or open sores on the lower legs points to chronic vein disease that benefits from treatment before it progresses.