Swollen ankles happen when fluid leaks out of your small blood vessels and collects in the tissue around your ankles and feet. This can be triggered by something as simple as sitting too long or eating a salty meal, or it can signal a more serious issue with your veins, heart, or kidneys. The key to figuring out what’s going on is noticing the pattern: whether one ankle or both are swollen, how quickly it came on, and what else you’re feeling.
How Fluid Ends Up in Your Ankles
Your body constantly moves fluid between your bloodstream and the surrounding tissue. Pressure inside your blood vessels pushes fluid out, while proteins in your blood (especially one called albumin) pull fluid back in. When that balance tips in either direction, fluid accumulates. Your ankles are a prime target because gravity pulls fluid downward throughout the day, and your lower legs are the farthest point from your heart.
Three things can tip that balance: higher pressure inside your blood vessels (from standing all day, excess salt, or a heart that isn’t pumping efficiently), leakier vessel walls (from inflammation or certain medications), or a backup in your lymphatic system, which normally drains excess fluid from your tissues. Most causes of swollen ankles involve one or more of these mechanisms.
Common Everyday Causes
Prolonged sitting or standing is the most frequent culprit. When your legs stay in one position for hours, your calf muscles aren’t contracting to push blood back up toward your heart. Fluid pools in your lower legs, and by evening your ankles look puffy. This is especially common during long flights, desk-bound workdays, or road trips.
High sodium intake plays a direct role. Sodium causes your body to hold on to water, increasing the volume of fluid in your bloodstream and raising pressure inside your vessels. The American Heart Association recommends staying under 1,500 mg of sodium per day, though the average person consumes well over that. Processed foods, restaurant meals, and canned soups are major sources. Cutting back on sodium often produces a noticeable reduction in ankle swelling within a few days.
Heat also contributes. In warm weather, your blood vessels dilate to release heat, which lowers the pressure that normally keeps fluid inside your veins. That’s why your shoes may feel tighter on a hot summer afternoon.
Venous Insufficiency
Chronic venous insufficiency affects about 1 in 20 adults and is one of the most common medical causes of persistent ankle swelling. Your leg veins contain one-way valves that keep blood flowing upward toward your heart. When those valves weaken or fail, blood flows backward (a condition called venous reflux) and pools in your lower legs. Over time, the increased pressure can even burst tiny capillaries near the skin surface.
The telltale pattern is swelling that worsens as the day goes on and improves overnight when you’re lying flat. You may also notice aching or heaviness in your legs, visible varicose veins, or skin that turns brownish near your ankles. About 1 in 3 adults have varicose veins, and each year roughly 1 in 50 of those people progress to chronic venous insufficiency.
Medications That Cause Swelling
Several common drug classes cause ankle swelling as a side effect. Calcium channel blockers, frequently prescribed for high blood pressure (amlodipine and nifedipine are the most widely used), widen the small arteries feeding your capillaries without equally widening the veins that drain them. The result is higher pressure inside the capillary bed, pushing fluid into surrounding tissue. This type of swelling typically appears within the first few weeks of starting the medication and affects both ankles equally.
Other medications linked to ankle swelling include diabetes drugs in the thiazolidinedione class (like pioglitazone), hormone therapies including estrogen and testosterone, some antidepressants, corticosteroids, and NSAIDs like ibuprofen and naproxen. If your swelling started around the time you began a new medication, that connection is worth discussing with whoever prescribed it. Stopping or switching the drug often resolves the swelling completely.
Heart, Kidney, and Liver Problems
When swelling appears in both ankles and comes on gradually over weeks, it can reflect a problem with a major organ. Heart failure is one of the more common causes: when the heart can’t pump blood efficiently, pressure builds in the veins leading back from your legs. This fluid backup shows up as swelling in both ankles and lower legs, often alongside shortness of breath, fatigue, or waking up at night to urinate.
Kidney disease reduces your body’s ability to filter excess sodium and water, leading to fluid retention throughout the body that tends to settle in the ankles. Liver disease, particularly cirrhosis, lowers the production of albumin, the protein responsible for pulling fluid back into your bloodstream. With less albumin, fluid leaks out more easily and accumulates in the legs and abdomen.
Pregnancy-Related Swelling
Swollen feet and ankles are extremely common during pregnancy, particularly in the third trimester. The growing uterus compresses the large veins returning blood from your legs, and hormonal changes make your blood vessels more permeable. Mild, symmetrical ankle swelling that fluctuates throughout the day is generally a normal part of pregnancy.
What’s not normal: sudden swelling in your face and hands, especially when paired with headaches, vision changes, or upper abdominal pain. These can be signs of preeclampsia, a serious blood pressure condition that develops after 20 weeks. Swollen feet alone are not typically a sign of preeclampsia, but swelling that rapidly extends to the face and hands warrants immediate medical attention.
One Ankle vs. Both Ankles
Whether one or both ankles are swollen is one of the most useful clues for narrowing down the cause.
Swelling in just one ankle raises concern for a blood clot (deep vein thrombosis, or DVT), especially if it came on suddenly and is accompanied by calf pain, warmth, or redness. DVT is a medical emergency because the clot can break loose and travel to your lungs. Other causes of one-sided swelling include ankle sprains and other injuries, infections like cellulitis (which also produces redness and warmth), and a fluid-filled cyst behind the knee called a Baker’s cyst. Among people evaluated for sudden swelling in one leg, about 40% turn out to have a muscle strain or twisting injury, while a smaller percentage have cellulitis or a cyst.
Swelling in both ankles is more likely a systemic issue: heart failure, kidney disease, venous insufficiency, medication side effects, or simply too much salt and too little movement. Both-sided swelling that worsens suddenly can indicate a flare of heart failure and deserves prompt evaluation.
Injury-Related Swelling
A sprained ankle causes rapid, localized swelling from inflammation as your body rushes blood and immune cells to the injured area. You’ll usually remember a specific moment of twisting or rolling your ankle. Mild sprains improve within a few days with rest, ice, and elevation. If swelling and pain haven’t improved after a day or two, or if you can’t bear weight on the ankle, you may be dealing with a more severe ligament tear or a fracture that needs imaging.
How Pitting Edema Is Graded
Doctors assess ankle swelling by pressing a finger into the swollen area for several seconds and watching what happens. If the pressure leaves a visible dent that takes time to fill back in, that’s called pitting edema. It’s graded on a scale from 1 to 4:
- Grade 1: A shallow 2 mm dent that rebounds immediately.
- Grade 2: A 3 to 4 mm dent that fills in within 15 seconds.
- Grade 3: A 5 to 6 mm dent that takes 15 to 60 seconds to rebound.
- Grade 4: An 8 mm dent that takes two to three minutes to fill back in.
Higher grades generally indicate more significant fluid accumulation and a greater likelihood that an underlying condition needs attention.
What You Can Do at Home
Elevating your legs above heart level for 20 to 30 minutes several times a day helps gravity work in your favor, draining fluid back toward your core. This is the simplest and most effective immediate measure for mild swelling from prolonged sitting or standing.
Compression stockings apply graduated pressure to your lower legs, supporting your veins and preventing fluid from pooling. Low-compression stockings (under 20 mmHg) are available without a prescription and work well for people who stand or sit for long stretches, or for pregnant women dealing with routine swelling. Stockings rated at 20 mmHg or higher require a prescription and are used for more significant venous problems.
Regular movement matters more than most people realize. Walking, calf raises, or even flexing your feet while seated activates the muscle pump in your lower legs that pushes blood back toward your heart. If you sit at a desk all day, getting up to walk for a few minutes every hour makes a measurable difference.
Reducing sodium intake is one of the most effective long-term strategies. Aiming for under 2,000 mg per day is a reasonable target for most people with fluid retention issues. Reading nutrition labels is the fastest way to identify where your sodium is coming from, since roughly 70% of dietary sodium in Western diets comes from packaged and restaurant foods rather than the salt shaker.