Swollen ankles and feet happen when fluid builds up in the tissues of your lower legs, a condition called peripheral edema. The causes range from something as simple as sitting too long or eating a salty meal to serious conditions involving your heart, kidneys, or veins. Whether the swelling affects one leg or both, and whether it came on suddenly or gradually, tells you a lot about what’s behind it.
How Fluid Ends Up in Your Feet
Your body constantly moves fluid between your bloodstream and your tissues. Gravity naturally pulls that fluid downward throughout the day, which is why your feet and ankles bear the brunt. Normally, your veins and lymphatic system push fluid back up toward your heart, and your kidneys filter out any excess. When any part of this system breaks down, fluid accumulates in the lowest points of your body.
The swelling itself falls into two broad categories. Pitting edema leaves a visible dent when you press a finger into the swollen area. Clinicians grade it on a 1 to 4 scale: grade 1 leaves a shallow 2 mm indent that bounces back immediately, while grade 4 creates an 8 mm pit that takes two to three minutes to refill. Non-pitting edema, which doesn’t indent, typically points to problems with the lymphatic system or thyroid rather than fluid overload.
One Leg vs. Both Legs
This distinction matters more than most people realize. When only one ankle or foot swells, the problem is almost always local, something happening in that specific leg. When both sides swell evenly, the cause is more likely systemic, meaning it involves your whole body.
The most urgent cause of one-sided swelling is a deep vein thrombosis (DVT), a blood clot in a deep leg vein. Other single-leg causes include muscle strains or tears (which account for about 40% of cases once a clot is ruled out), infections, a ruptured cyst behind the knee, and lymphatic blockage. About 26% of one-sided swelling cases have no identifiable cause even after testing.
Both-sides swelling points toward heart failure, kidney problems, liver disease, medications, or prolonged inactivity. Sorting out which one requires looking at your other symptoms and health history.
Heart Failure
Heart failure is one of the most common serious causes of bilateral ankle swelling, especially in older adults. When the heart can’t pump blood efficiently, it backs up like a bottleneck in a shipping department. Blood pools in the veins of your legs and feet, and the increased pressure forces fluid out of your blood vessels and into surrounding tissues.
Left-sided heart failure is the most common trigger for right-sided heart failure, which is the side directly responsible for leg swelling. When the left ventricle can’t keep up, blood backs up into the lungs first, then eventually overwhelms the right side of the heart too. The swelling tends to worsen over the course of the day and improve overnight when you’re lying flat. You might also notice shortness of breath, fatigue, and a need to prop yourself up on pillows to sleep comfortably.
Kidney and Liver Disease
Your kidneys regulate how much sodium and water your body retains. When they’re damaged, they hold onto sodium, and water follows. This expands your total fluid volume and pushes excess fluid into your tissues, particularly your feet, ankles, and around your eyes.
Liver cirrhosis causes swelling through a different mechanism. A damaged liver produces less albumin, a protein that acts like a sponge to keep fluid inside your blood vessels. When albumin drops, fluid leaks out of your bloodstream and into surrounding tissues. Cirrhosis also causes the body to retain sodium aggressively, compounding the problem. The swelling often shows up in the abdomen first (as ascites) and then in the legs and feet.
Chronic Venous Insufficiency
Your leg veins contain one-way valves that help push blood upward against gravity, back toward your heart. When those valves weaken or become damaged, blood flows backward and pools in the lower legs. This condition, called chronic venous insufficiency, is extremely common, and it gets worse over time if untreated.
The pooled blood raises pressure inside the veins, forcing fluid into the tissues and causing persistent swelling around the ankles. Over months and years, the skin on your lower legs can change color to a reddish-brown, become leathery in texture, and eventually break down into open sores near the ankles. In severe cases, scar tissue forms in the lower leg, trapping fluid permanently and making the calf feel hard and enlarged. Risk factors include a history of blood clots, varicose veins, obesity, pregnancy, and jobs that require prolonged standing.
Medications That Cause Swelling
Several common medications cause ankle swelling as a side effect, and blood pressure drugs called calcium channel blockers are the most frequent culprit. These medications relax blood vessels to lower blood pressure, but they relax arteries more than veins. The mismatch increases pressure in the tiny capillaries of your legs and pushes fluid into the tissues.
The swelling is dose-dependent. At standard doses, it affects roughly 1 to 15% of patients. At high doses taken long-term, the incidence can exceed 80%. Adding a second type of blood pressure medication can cut the swelling roughly in half: one trial found that combining a calcium channel blocker with another agent reduced edema from 18.7% to 7.6% of patients.
Other medications that commonly cause ankle swelling include hormone therapies (estrogen, testosterone), certain diabetes drugs, anti-inflammatory painkillers like ibuprofen, and some antidepressants. If your swelling started around the same time as a new prescription, the timing is worth noting.
Pregnancy-Related Swelling
Some ankle swelling during pregnancy is normal, particularly in the third trimester. Your blood volume increases by nearly 50%, and the growing uterus puts pressure on the veins returning blood from your legs. Most of this swelling is harmless and resolves after delivery.
The concern is preeclampsia, a condition that develops after 20 weeks of pregnancy and involves high blood pressure (140/90 mm Hg or higher) along with signs of organ stress. Sudden, severe swelling in the face, hands, or feet can be an early warning sign, especially when paired with headaches, vision changes, upper belly pain, or nausea. Preeclampsia can also develop in the weeks after delivery, so those symptoms remain relevant postpartum.
Everyday Causes
Not all ankle swelling signals a medical problem. Gravity and inactivity are the simplest explanation for many people. Sitting at a desk all day, taking a long flight, or standing for hours at work allows fluid to pool in your feet simply because there’s nothing pushing it back up. Your calf muscles act as a pump for your veins, and when they’re not contracting, fluid accumulates.
A high-sodium diet contributes by causing your kidneys to retain extra water. Hot weather dilates blood vessels and increases fluid leakage into tissues. Carrying extra body weight puts more pressure on your leg veins and makes it harder for fluid to return to your heart. An ankle injury, even a minor sprain, triggers localized inflammation and swelling as part of the healing process.
Reducing Swelling at Home
The most effective immediate remedy is elevation. Lie down and raise your feet above the level of your heart, which reverses gravity’s effect and helps fluid drain back into your bloodstream. Doing this for 20 to 30 minutes several times a day makes a noticeable difference for most causes of mild swelling.
Movement helps too. Walking, ankle circles, or simply flexing your calves while seated activates the muscle pump in your legs. Compression socks apply gentle, graduated pressure that supports your veins and prevents fluid from settling into your tissues. They’re particularly useful if you stand or sit for long stretches. Reducing your salt intake also helps by lowering the amount of water your body holds onto.
These strategies work well for everyday swelling and mild venous insufficiency. They won’t resolve swelling caused by heart failure, kidney disease, blood clots, or other systemic conditions, which require treatment of the underlying problem. Swelling that appears suddenly in one leg, comes with chest pain or shortness of breath, doesn’t improve with elevation, or worsens over days deserves prompt medical evaluation.