Persistent swelling in both ankles most commonly results from weakened valves in your leg veins, a condition called chronic venous insufficiency. But it can also signal fluid retention from heart, kidney, liver, or thyroid problems, or be a side effect of certain medications. The word “always” matters here: swelling that never fully resolves points to an ongoing issue rather than a one-time injury, and figuring out the underlying cause is the key to making it stop.
The Most Common Cause: Weak Vein Valves
Your leg veins contain one-way valves that push blood upward against gravity, back toward your heart. When those valves weaken or stop closing properly, blood pools in the lower legs. That pooling increases pressure inside the veins, forcing fluid out into the surrounding tissue. The result is swelling that tends to worsen through the day, especially if you’ve been standing or sitting for long stretches, and improves overnight when your legs are level with your heart.
Over time, untreated venous insufficiency does more than cause puffiness. The constant high pressure can burst tiny capillaries near the skin’s surface, leaving a reddish-brown discoloration on the lower legs. The skin becomes fragile and prone to open sores called venous ulcers, which heal slowly and can become infected. In severe cases, scar tissue forms in the calf, trapping fluid permanently and making the lower leg feel hard to the touch. Varicose veins often accompany this process.
Heart, Kidney, and Liver Problems
When your heart can’t pump blood efficiently, pressure backs up into the veins, and fluid leaks into the tissues of your feet and ankles. This is one of the hallmark signs of heart failure, and the swelling tends to affect both legs equally. It often comes with other symptoms: shortness of breath, fatigue, or waking up at night gasping for air.
Your kidneys filter excess fluid and sodium from the blood. When they aren’t working well, that fluid stays in your body and settles in the lowest point, your ankles. Liver disease works through a different mechanism: a damaged liver produces less of the blood protein that holds fluid inside your blood vessels, so fluid seeps out into surrounding tissues. Thyroid disorders and severe anemia can also cause the body to retain fluid in similar ways.
If your ankle swelling is accompanied by fatigue, unexplained weight gain, reduced urine output, or abdominal bloating, one of these organ-level problems may be driving it. A basic set of blood and urine tests can screen for most of them relatively quickly.
Medications That Cause Swelling
Several common medications cause ankle swelling as a side effect, and it’s worth checking your prescription list before assuming something more serious is going on. Calcium channel blockers, a widely prescribed class of blood pressure medications, are among the most frequent culprits. The swelling is dose-related: it occurs in roughly 1 to 15% of people at standard doses, but at higher long-term doses, the rate can exceed 80%.
Other drugs known to cause fluid retention include certain diabetes medications, steroids like prednisone, hormone therapies (including estrogen), and common over-the-counter painkillers like ibuprofen and naproxen. If your swelling started or worsened around the time you began a new medication, that connection is worth raising with whoever prescribed it. Switching to an alternative or adjusting the dose often resolves the problem.
Lymphedema: A Different Type of Swelling
Not all ankle swelling involves fluid that sloshes around freely. Lymphedema happens when the lymphatic system, your body’s network for draining excess fluid and waste from tissues, becomes blocked or damaged. The fluid that accumulates is thicker and richer in protein than regular swelling, and over time it triggers inflammation and scarring in the skin and tissue underneath.
One way to distinguish lymphedema from other types of swelling is by pressing your finger into the swollen area. With most causes of edema, your finger leaves a temporary dent (called pitting). With advanced lymphedema, the tissue feels firm and doesn’t indent because fibrosis has stiffened the skin. Another hallmark: the skin on top of the toes or foot becomes so thick you can’t pinch it into a fold. This thickening is fairly specific to lymphedema and helps separate it from swelling caused by vein or organ problems. That said, early-stage lymphedema can still pit, so the absence of firmness doesn’t rule it out.
Heat, Salt, and Gravity
Some causes of persistent ankle swelling are more mundane. Warm weather dilates the small blood vessels in your skin to release heat, and that dilation lets more fluid than usual leak into the tissues of your lower legs. If you live in a hot climate or notice your ankles swell most in summer, this is likely a contributing factor.
High sodium intake is another major driver. Sodium causes your body to hold onto water, increasing overall fluid volume. The World Health Organization recommends staying under 2,000 mg of sodium per day (just under a teaspoon of table salt), but most people consume well over that. Processed foods, restaurant meals, and canned soups are common sources of hidden sodium. Reducing your intake can make a noticeable difference in swelling within days.
Prolonged sitting or standing also plays a straightforward role. Gravity pulls fluid downward, and without the muscle contractions of walking to pump blood back up through your veins, it accumulates at the ankles. People with desk jobs or those who stand in one place for hours are especially susceptible.
When Swelling Is an Emergency
Sudden swelling in one ankle or leg, not both, raises concern for a deep vein thrombosis (DVT), a blood clot in a deep leg vein. Warning signs include pain or tenderness that worsens when you stand or walk, warmth in the swollen area, and skin that looks red or discolored. Some people notice the veins near the skin’s surface look larger than usual. A DVT can break loose and travel to the lungs, causing chest pain, sudden shortness of breath, coughing up blood, or fainting. This is a medical emergency.
If your chronic bilateral swelling suddenly becomes much worse, or you develop new shortness of breath, rapid weight gain (several pounds in a few days), or significantly reduced urine output, these can indicate worsening heart or kidney function and warrant prompt evaluation.
How Chronic Ankle Swelling Is Diagnosed
Doctors typically start with a physical exam and basic lab work: tests that check heart function, thyroid levels, liver enzymes, kidney function, and protein levels in your urine. These screenings can identify or rule out most systemic causes in a single round of bloodwork.
If venous insufficiency is suspected, a duplex ultrasound of the leg veins can show whether your vein valves are leaking or whether there’s an obstruction. For sudden one-sided swelling, the evaluation is more urgent. Patients at lower risk for DVT typically get a blood test that’s highly sensitive for clots (it catches about 96% of them). If that test is positive, or if the risk of DVT seems higher, an ultrasound of the leg veins follows.
When the labs and ultrasound suggest heart involvement, an echocardiogram (an ultrasound of the heart) can assess how well it’s pumping and whether fluid is backing up.
Managing the Swelling
Treatment depends entirely on the cause, but a few strategies help across nearly all types of ankle edema. Compression stockings are the most widely used tool. For mild, everyday swelling, stockings rated at 15 to 20 mmHg of pressure provide gentle support. More significant swelling from venous insufficiency or lymphedema typically requires 30 to 40 mmHg, and severe cases with hardened tissue changes may need 40 to 50 mmHg or above, fitted under clinical guidance.
Elevating your legs above heart level for 20 to 30 minutes several times a day helps fluid drain back toward your core. Regular walking activates the calf muscles, which act as a pump to push blood upward through the veins. Even short, frequent walks throughout the day are more effective than one long walk followed by hours of sitting.
Cutting sodium intake below 2,000 mg per day reduces the amount of fluid your body retains. This means reading nutrition labels carefully: a single serving of canned soup or deli meat can contain over half a day’s recommended sodium. Staying well hydrated paradoxically helps too, because mild dehydration signals your kidneys to hold onto more water and sodium rather than release them.
For swelling driven by a specific medical condition, treating that condition is what ultimately resolves the edema. Medication adjustments, treatments to improve vein function, and therapies targeting heart or kidney disease all address the root problem rather than just managing symptoms at the ankle.