Swollen ankles are usually a sign that fluid is building up in the soft tissues of your lower legs, a condition called peripheral edema. In most cases, the cause is something manageable like prolonged sitting, too much salt, or a medication side effect. But ankle swelling can also be an early warning sign of heart, kidney, liver, or vein problems, so understanding the pattern of your swelling matters.
Whether one ankle is puffy or both legs are ballooning by evening, the details tell very different stories. Here’s what to pay attention to and what each pattern typically means.
One Swollen Ankle vs. Both
The single most useful clue is whether the swelling affects one leg or both. Swelling in just one ankle points to a local problem in that limb. The most common cause of ongoing one-sided swelling is chronic venous disease, where damaged valves in the leg veins allow blood to flow backward and pool under the force of gravity. You might also notice skin discoloration or small ulcers near the ankle over time.
One-sided swelling that comes on suddenly is a different situation. About 40% of acute cases turn out to be a muscle strain, tear, or twisting injury. But the concern doctors prioritize first is a deep vein thrombosis (DVT), a blood clot in a deep leg vein. A DVT can cause warmth, pain, and redness in the affected leg. It matters because a clot can break loose and travel to the lungs, causing a pulmonary embolism. If you develop sudden swelling in one leg along with sharp chest pain, trouble breathing, a fast heartbeat, or coughing up blood, that combination needs emergency attention.
Other causes of one-sided swelling include cellulitis (a skin infection that produces redness, warmth, and sometimes fever), a Baker’s cyst behind the knee that has ruptured, and lymphedema from blocked or damaged lymph vessels, sometimes after surgery or radiation therapy.
When both ankles swell at roughly the same rate, the cause is almost always something affecting your whole body rather than one leg. Heart failure, kidney disease, liver problems, and medications top the list.
Heart Failure and Fluid Buildup
Heart failure is one of the most common systemic causes of bilateral ankle swelling, especially in older adults. When the heart can’t pump blood efficiently, the flow slows down. Blood backs up in the veins returning to the heart, and the rising pressure forces fluid out of blood vessels and into surrounding tissues. Because gravity pulls that fluid downward, it collects first in your feet and ankles.
The swelling from heart failure tends to worsen throughout the day and improve overnight when you’re lying flat. You might also notice shortness of breath, fatigue, or needing extra pillows to sleep comfortably. Weight that creeps up by several pounds over just a few days is another signal, since that rapid gain is almost entirely retained fluid rather than body fat.
Kidney and Liver Disease
Your kidneys regulate how much sodium and water your body holds onto. When they aren’t filtering properly, excess fluid accumulates throughout the body. Swelling often appears in the ankles and feet but can also show up around the eyes and in the hands, particularly in the morning.
Liver disease, especially advanced scarring (cirrhosis), disrupts the production of a key blood protein that helps keep fluid inside your blood vessels. Without enough of it, fluid leaks into tissues. Liver-related swelling often appears alongside a visibly swollen abdomen, where fluid collects in the abdominal cavity.
Vein Valve Failure
Chronic venous insufficiency (CVI) is an extremely common cause of ankle swelling that many people live with for years without a clear diagnosis. The valves inside your leg veins are supposed to act as one-way gates, pushing blood upward toward the heart with each muscle contraction. When those valves weaken or become damaged, blood flows backward and pools in the lower legs. The resulting pressure increase forces fluid into the surrounding tissue.
CVI swelling follows a predictable pattern: minimal in the morning, progressively worse after standing or sitting for hours, and most noticeable at the end of the day. Over time, the chronic pressure can darken the skin around the ankles, make it feel leathery or tight, and eventually lead to open sores that are slow to heal. A history of blood clots, varicose veins, or previous leg injuries raises your risk.
Medications That Cause Swelling
Several widely prescribed drugs list ankle swelling as a side effect. Calcium channel blockers, a class of blood pressure medications, are among the most common culprits. The swelling they cause is dose-related. At low doses, roughly 1 to 15% of people notice it. At high doses taken long-term, that number can exceed 80%.
Other medications linked to peripheral edema include certain pain relievers (particularly anti-inflammatory drugs like ibuprofen and naproxen), some diabetes medications, hormone therapies including estrogen and testosterone, and steroids. If your swelling started or worsened after beginning a new medication, that timing is worth mentioning to your doctor. Stopping or adjusting the dose often resolves the problem, but never discontinue a prescribed medication on your own.
Pregnancy and Preeclampsia
Mild ankle swelling during pregnancy is normal, particularly in the third trimester. The growing uterus compresses veins in the pelvis, slowing blood return from the legs, and hormonal shifts cause the body to retain more fluid.
What isn’t normal is sudden swelling, especially in the face and hands. A rapid jump in weight or a sudden appearance of edema can signal preeclampsia, a serious pregnancy complication involving high blood pressure and organ stress. Preeclampsia can develop after the 20th week of pregnancy and requires close monitoring. Sudden puffiness combined with severe headaches, vision changes, or upper abdominal pain warrants immediate medical evaluation.
How to Check the Severity
You can gauge how much fluid has accumulated with a simple test: press your thumb firmly into the swollen area for a few seconds, then release. If an indentation remains, that’s called pitting edema, and its depth tells you roughly how severe the swelling is.
- Grade 1: A shallow 2 mm pit that rebounds immediately. This is mild.
- Grade 2: A 4 mm pit that fills back in within about 15 seconds.
- Grade 3: A 6 mm pit in a visibly swollen leg, taking up to 30 seconds to rebound.
- Grade 4: An 8 mm pit with significant distortion of the limb, taking more than 30 seconds to fill back in.
Grade 1 swelling that comes and goes with activity or heat is rarely urgent. Grade 3 or 4 pitting, or any grade that appears suddenly, deserves a medical workup.
Everyday Factors That Make It Worse
Even without an underlying disease, certain habits promote fluid retention in the ankles. High sodium intake is the biggest dietary factor. Salt causes your body to hold onto water, and the excess fluid tends to settle in the lowest point, your feet and ankles, especially if you’ve been sitting or standing in one position for hours. Keeping sodium intake moderate is a practical first step for anyone dealing with recurrent swelling.
Heat also plays a role. Blood vessels expand in warm weather to help cool your body, and some fluid escapes into surrounding tissues in the process. Long flights or car rides compound the effect by keeping your legs bent and immobile for hours, slowing venous return.
Practical Ways to Reduce Swelling
For mild, non-emergency swelling, a few strategies can make a noticeable difference. Elevating your legs above heart level for 15 to 20 minutes several times a day helps gravity drain fluid back toward your core. Regular walking activates the calf muscles, which act as a pump to push blood upward through your veins.
Compression stockings apply graduated pressure that is strongest at the ankle and lighter toward the knee, counteracting fluid pooling. Low compression stockings (under 20 mmHg) are available without a prescription and work well for mild end-of-day swelling. Medium compression (20 to 30 mmHg) is typically recommended for chronic venous insufficiency, and high compression (above 30 mmHg) is reserved for more severe cases and usually requires a fitting.
Reducing sodium, staying hydrated (which paradoxically helps your body release excess fluid rather than hold it), and moving your ankles in circles during long periods of sitting all contribute to keeping swelling in check. These measures help manage symptoms, but persistent or worsening edema still calls for identifying and treating whatever is driving it.