Swollen ankles happen when fluid leaks out of your blood vessels and collects in the tissue around your ankles and feet. This fluid buildup, called edema, can result from something as simple as sitting too long or eating a salty meal, or it can signal a more serious problem with your heart, kidneys, or veins. Understanding the pattern of your swelling, whether it affects one leg or both, and how quickly it appeared will help you figure out what’s going on.
How Fluid Ends Up in Your Ankles
Your body constantly balances fluid between your bloodstream and the surrounding tissues. Two main forces keep this balance in check: the pressure inside your blood vessels pushing fluid out, and proteins in your blood pulling fluid back in. When either force shifts, fluid escapes into the spaces between your cells. Gravity does the rest, dragging that extra fluid down to the lowest point in your body: your ankles and feet.
Your lymphatic system normally acts as a drainage network, collecting stray fluid and returning it to your bloodstream. Edema develops when the rate of fluid leaking out of your capillaries outpaces your lymphatic system’s ability to drain it away. The swelling typically starts around the ankle bone and works its way up the leg as more fluid accumulates.
Common Everyday Causes
For many people, swollen ankles aren’t a medical emergency. They’re the result of daily habits and circumstances that temporarily tip the fluid balance.
Prolonged sitting or standing. When your legs stay in one position for hours, whether on a long flight, at a desk, or on your feet at work, your calf muscles aren’t contracting. Those muscles normally squeeze blood upward through your veins like a pump. Without that pumping action, blood pools in your lower legs and fluid seeps into the surrounding tissue.
Too much sodium. Salt causes your body to hold onto water. If your ankles tend to puff up after a restaurant meal or a day of snacking on processed food, sodium is a likely culprit. Keeping your daily intake between 1,500 and 2,300 milligrams can help you determine whether salt is driving your swelling.
Heat. Warm weather dilates your blood vessels, which increases the pressure pushing fluid out of your capillaries and into surrounding tissue. This is why ankles that are fine in winter may swell noticeably in summer.
Medications That Cause Ankle Swelling
Several common prescription drugs list ankle swelling as a side effect, and one class stands out. Calcium channel blockers, a widely prescribed group of blood pressure medications, cause ankle edema in 1 to 15 percent of patients at standard doses. At higher doses taken long term, that number can exceed 80 percent. The swelling happens because these drugs relax blood vessel walls, increasing the pressure that pushes fluid into tissues.
If you take a calcium channel blocker and notice puffy ankles, don’t stop the medication on your own. In clinical trials, adding a second type of blood pressure drug (one that targets the body’s salt and fluid regulation system) reduced the incidence of ankle swelling by 38 percent compared to taking the calcium channel blocker alone. Your prescriber can adjust your regimen. Other drugs that commonly cause ankle swelling include anti-inflammatory painkillers, steroids, certain diabetes medications, and some antidepressants.
Vein Problems: Chronic Venous Insufficiency
Your leg veins contain a series of one-way valves that open to let blood flow upward toward your heart and snap shut to prevent it from falling back down. Over time, these valves can weaken or fail. When they do, blood flows backward (a process called reflux) and pools in the lower legs. The resulting pressure buildup forces fluid, proteins, and even red blood cells out through the capillary walls and into surrounding tissue.
Chronic venous insufficiency is one of the most common causes of persistent ankle swelling, especially if you notice it worsening throughout the day and improving overnight. Visible varicose veins, skin discoloration around the ankles (often brownish or reddish), and a heavy or achy feeling in the legs are telltale signs. A duplex ultrasound with reflux testing can confirm the diagnosis by mapping how blood moves through your leg veins.
Organ-Related Causes
When ankle swelling is caused by a problem with a major organ, it almost always affects both legs.
Heart failure. When the heart can’t pump blood efficiently, blood backs up in the veins leading to the heart. This raises pressure in the leg veins, pushing fluid into the tissues of the ankles, feet, and calves. The swelling is often worse at the end of the day and may be accompanied by shortness of breath or fatigue.
Kidney disease. Your kidneys regulate how much fluid and salt stay in your blood. When they’re damaged, excess fluid and sodium build up. Kidney-related edema often appears in the legs and around the eyes. A more specific form of kidney damage called nephrotic syndrome causes the kidneys to leak protein into your urine, lowering the protein levels in your blood. Since blood proteins are what pull fluid back into your vessels, losing them leads to widespread swelling.
Liver disease. Cirrhosis and other forms of severe liver damage reduce the liver’s ability to produce albumin, the main protein responsible for keeping fluid inside blood vessels. The result is fluid buildup in the abdomen and legs.
One Swollen Ankle Is Different
Swelling in just one leg deserves separate attention because it raises the possibility of a blood clot. Deep vein thrombosis (DVT) occurs when a clot forms in one of the deep veins of the leg, blocking blood flow and causing fluid to back up on one side. The classic signs include swelling in one leg only, pain or cramping that often starts in the calf, warmth in the affected area, and skin that turns red or purple.
DVT is a medical emergency because the clot can break loose and travel to your lungs. If you develop sudden, painful swelling in one leg, especially after surgery, a long period of immobility, or a long flight, seek immediate medical attention. Doctors use a scoring system called the Wells criteria to estimate your risk, then confirm the diagnosis with either a blood test or an ultrasound of the leg veins.
Swollen Ankles During Pregnancy
Mild swelling in the feet and ankles is a normal part of pregnancy, particularly in the third trimester, as the growing uterus puts pressure on the veins returning blood from the legs. This kind of swelling develops gradually and affects both feet.
What’s not normal is sudden swelling, especially in the face or hands, or a rapid worsening of leg swelling. These can be signs of preeclampsia, a pregnancy complication involving high blood pressure that can become dangerous for both mother and baby. Painful swelling in just one leg during pregnancy can also indicate a blood clot, since pregnancy increases clotting risk. Contact your healthcare provider right away if swelling appears suddenly or escalates quickly.
How to Check Your Own Swelling
You can gauge the severity of your ankle swelling at home using the same technique clinicians use. Press your thumb firmly into the skin over the top of your foot or just behind your ankle bone for at least two seconds, then release. If your thumb leaves a visible dent, that’s called pitting edema, and the depth and recovery time tell you how severe it is.
- Grade 1: A shallow pit (about 2 mm) that bounces back immediately. This is mild.
- Grade 2: A slightly deeper pit (about 4 mm) that fills back in within 15 seconds.
- Grade 3: A noticeable pit (about 6 mm) in a visibly swollen leg, taking up to 30 seconds to rebound.
- Grade 4: A deep pit (about 8 mm) in a grossly swollen leg that takes more than 30 seconds to fill back in.
Tracking your grade over days or weeks gives you useful information to share with a doctor and helps you notice whether your swelling is stable or getting worse.
What Doctors Look For
If your ankle swelling persists or you can’t explain it with an obvious trigger like heat or a long day on your feet, a doctor will typically start with blood and urine tests. These check how well your heart, kidneys, liver, and thyroid are functioning and whether you’re losing protein through your urine. A specific blood marker called BNP (brain natriuretic peptide) rises when the heart is under strain, and elevated levels prompt an echocardiogram to evaluate heart function.
For one-sided swelling, the priority is ruling out a blood clot. Patients with lower risk get a blood test first (the d-dimer, which is 96 percent sensitive for clots). Those at higher risk go straight to a compression ultrasound of the leg. For chronic swelling that points toward vein problems, a duplex ultrasound with reflux testing maps the blood flow in your veins and identifies any faulty valves.
Reducing Swelling at Home
The single most effective thing you can do for swollen ankles is elevate your legs above the level of your heart. Lying on a couch with your feet propped on two or three pillows, or lying on the floor with your legs up against a wall, lets gravity work in your favor and helps fluid drain back toward your core. Doing this for 20 to 30 minutes several times a day makes a noticeable difference for most people.
Movement matters just as much. Walking, flexing your feet, or doing calf raises activates the muscle pump in your lower legs that pushes blood upward through your veins. If your job keeps you seated, set a reminder to get up and move every hour. Compression stockings provide steady external pressure that supports your veins and limits fluid from escaping into the tissues. If you have any signs of poor circulation in your legs, such as numbness, color changes, or wounds that heal slowly, get checked before using compression stockings, since they can worsen certain arterial conditions.
Cutting back on sodium, staying hydrated (which paradoxically helps your body release excess fluid rather than hoard it), and limiting alcohol all support your body’s natural fluid regulation. These measures won’t fix swelling caused by a failing organ or damaged veins, but they can meaningfully reduce the day-to-day puffiness that many people experience.