Ankle swelling happens when fluid leaks out of your blood vessels and gets trapped in the surrounding tissue. The most common causes are prolonged standing or sitting, too much salt in your diet, venous insufficiency, and medication side effects. Sometimes, though, swollen ankles signal something more serious like heart failure, kidney disease, or a blood clot.
Whether the swelling affects one ankle or both, came on suddenly or built up over weeks, tells you a lot about what’s behind it.
How Fluid Ends Up in Your Ankles
Your body constantly moves fluid between your bloodstream and the tissue around it. Several forces keep this exchange balanced: the pressure inside your blood vessels pushing fluid out, proteins in your blood (especially albumin) pulling fluid back in, the integrity of your vessel walls, and your lymphatic system draining any excess. When any of these forces shifts, fluid accumulates in your tissues. Gravity pulls that excess fluid downward, which is why the ankles and feet are usually the first place you notice it.
It takes a meaningful shift to produce visible swelling. Studies show that capillary pressure needs to increase by about 15 mmHg above normal before edema becomes clinically noticeable. Your body has a significant buffer, which means that by the time you can see or feel the puffiness, something has already pushed your fluid balance well past its tipping point.
One Ankle vs. Both Ankles
This distinction matters more than most people realize. Swelling in just one ankle typically points to a local problem: an injury, infection, blood clot, or a vein issue in that specific leg. Swelling in both ankles usually means something systemic is going on, like heart failure, kidney or liver disease, medication side effects, or hormonal changes.
There are exceptions. Venous insufficiency and lymphedema can affect both legs but are often uneven, with one side worse than the other. And sometimes you can have a local problem in one leg layered on top of a systemic condition, making one ankle noticeably more swollen than the other.
Venous Insufficiency
This is one of the most common causes of chronic ankle swelling, particularly in people over 50. 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. That pooling raises pressure inside the veins, forcing fluid into the surrounding tissue.
The hallmark pattern is swelling that worsens as the day goes on, especially after long periods of standing, and improves overnight when your legs are flat. Over time, the sustained pressure can burst tiny capillaries, causing skin discoloration around the ankles (often reddish-brown or purplish). In severe cases, the chronic swelling creates scar tissue that traps even more fluid, making the problem progressively harder to reverse.
Heart, Kidney, and Liver Disease
When your heart can’t pump efficiently, blood backs up in the veins, raising pressure throughout the system. Your kidneys respond by holding onto sodium and water, which only adds to the fluid overload. This cycle between the heart and kidneys is central to the swelling seen in heart failure, and it’s why ankle edema is often one of the earliest visible signs of the condition.
Kidney disease causes swelling through a different path. Damaged kidneys can’t filter sodium and water properly, so excess fluid simply accumulates. They may also leak protein into the urine, lowering the albumin levels in your blood. Since albumin is the main protein that pulls fluid back into your vessels, losing it means fluid stays in your tissues instead.
Liver disease, particularly cirrhosis, reduces albumin production and raises pressure in the veins draining the abdomen, both of which contribute to fluid buildup in the legs and belly.
Medications That Cause Swelling
Several widely prescribed drug classes can cause ankle swelling as a side effect. If your swelling started shortly after beginning a new medication or increasing a dose, this is worth considering.
- Blood pressure medications (calcium channel blockers): These are among the most common culprits. They dilate arteries but not veins, creating a pressure imbalance that pushes fluid into tissues. Peripheral edema is a well-known and frequent side effect of this class.
- Anti-inflammatory painkillers (NSAIDs): Both over-the-counter options like ibuprofen and prescription versions cause the kidneys to retain sodium and water, raising blood volume and pressure.
- Diabetes medications (thiazolidinediones): These drugs promote fluid retention and are a recognized cause of peripheral edema.
- Nerve pain medications (gabapentin and pregabalin): These block certain calcium channels in a way that can produce edema similar to blood pressure medications.
- Steroids: Particularly those with mineralocorticoid activity, which increases sodium and water retention by the kidneys.
- Insulin: Starting or intensifying insulin therapy after a period of poorly controlled blood sugar can trigger a condition called insulin edema syndrome.
Dopamine agonists used for Parkinson’s disease, certain antipsychotics, and nitrate medications for chest pain can also contribute. If you suspect a medication is causing your swelling, don’t stop it on your own, but it’s a conversation worth having with whoever prescribed it.
Too Much Sodium
Sodium acts like a sponge for water in your body. When you eat more salt than your kidneys can efficiently clear, your blood volume expands and the extra pressure pushes fluid into your tissues. Current guidelines recommend keeping sodium between 1,500 and 3,000 mg per day, but the average intake in many Western diets far exceeds that range.
For people with heart failure, excess sodium is the primary driver of the fluid overload that leads to swollen ankles, belly swelling, and shortness of breath. But even in otherwise healthy people, a very salty meal can produce noticeable puffiness in the ankles and fingers the next morning. The effect is more pronounced in hot weather, during long flights, or after extended sitting.
Pregnancy Swelling and Warning Signs
Mild ankle swelling during pregnancy is extremely common and usually harmless. The growing uterus compresses veins in the pelvis, slowing blood return from the legs, while hormonal shifts and increased blood volume contribute to fluid retention.
The concern is preeclampsia, a serious condition defined by new-onset high blood pressure (140/90 or higher) and protein in the urine after 20 weeks of pregnancy. Sudden, severe swelling, particularly in the face and hands rather than just the ankles, can be an early sign. Other warning symptoms include persistent headaches, vision changes (blurriness, seeing spots), and pain in the upper right abdomen. Preeclampsia with severe features involves blood pressure at or above 160/110 and can affect the liver, kidneys, and brain. This requires urgent medical attention.
Blood Clots: When Swelling Is an Emergency
A deep vein thrombosis (DVT), a blood clot in a deep leg vein, typically causes swelling in just one leg. The classic signs are leg pain or cramping that often starts in the calf, skin that looks red or purple, and warmth over the affected area. The swelling tends to come on over hours to days rather than gradually over weeks.
The danger with a DVT is that the clot can break loose and travel to the lungs, causing a pulmonary embolism. Sudden shortness of breath, chest pain that worsens with deep breaths, a rapid pulse, dizziness or fainting, and coughing up blood are all signs that require emergency care immediately.
Risk factors for DVT include recent surgery, prolonged immobility (long flights, bed rest), cancer, pregnancy, obesity, and a personal or family history of blood clots.
Reducing Ankle Swelling at Home
For swelling caused by gravity, inactivity, or mild venous insufficiency, a few strategies make a real difference.
Elevating your legs above heart level for about 15 minutes, three to four times a day, lets gravity work in your favor and helps fluid drain back toward your core. Lying on a couch with your feet propped on two or three pillows generally achieves the right height. Consistency matters more than doing one long session.
Compression stockings apply graduated pressure that supports your veins and prevents fluid from settling. Research shows that even light compression in the 10 to 15 mmHg range is effective at preventing and reducing occupational swelling in people who stand or sit for long periods. Stockings in the 15 to 20 mmHg range are widely available without a prescription and work well for mild to moderate edema. Higher-pressure garments (20 to 30 mmHg) are typically reserved for diagnosed venous insufficiency.
Moving your calf muscles throughout the day, even just flexing your feet at your desk or taking short walks, activates the muscle pump that pushes blood back up your leg veins. Cutting back on sodium, staying hydrated, and avoiding sitting or standing in one position for hours at a time all help reduce the fluid retention that feeds ankle swelling.