Swollen feet and ankles happen when excess fluid collects in the tissues of your lower legs. This is called peripheral edema, and it ranges from a harmless response to gravity and salt intake all the way to a warning sign of heart, kidney, or liver problems. The cause depends heavily on whether the swelling affects both legs or just one, how quickly it appeared, and what other symptoms come with it.
How Fluid Ends Up in Your Feet
Your body constantly moves fluid between your bloodstream and the tissues around it. Swelling happens when that balance tips in favor of fluid leaking out and staying out. Five things can throw off this balance: pressure inside your blood vessels gets too high, the proteins that normally pull fluid back into your vessels drop too low, your blood vessel walls become leakier than usual, the surrounding tissues pull in extra fluid, or your lymphatic system (the drainage network that returns fluid to your bloodstream) stops working properly.
Gravity makes your feet and ankles the first place this shows up. Blood has to travel the longest distance back to your heart from your lower legs, and if anything slows that return trip, fluid pools at the bottom.
Common Everyday Causes
Most people with occasional foot swelling don’t have a serious medical condition. Standing or sitting in one position for hours, especially during long flights or desk jobs, slows blood flow back up your legs. High sodium meals cause your kidneys to hold onto extra water, and that fluid tends to settle in your feet by the end of the day. Hot weather dilates blood vessels near the skin, which lets more fluid seep into surrounding tissues.
Carrying extra body weight puts additional pressure on the veins in your legs, making it harder for blood to return to the heart efficiently. Pregnancy also causes swelling in the feet and ankles because blood volume increases significantly and the growing uterus puts pressure on pelvic veins. Some swelling during pregnancy is normal, but swelling that suddenly extends to the face and hands can signal preeclampsia, a serious blood pressure condition that needs immediate medical attention.
Medications That Cause Swelling
Several common medications list ankle swelling as a side effect. Blood pressure drugs called calcium channel blockers are among the most frequent culprits. The swelling is dose-related: at lower doses, roughly 1 to 15% of people experience it, but at higher long-term doses, the rate can exceed 80%. This happens because these drugs relax blood vessel walls, which lets more fluid leak into surrounding tissues.
Other medications that commonly cause foot and ankle swelling include anti-inflammatory painkillers (like ibuprofen and naproxen), steroids, certain diabetes medications, and some hormone therapies including estrogen. If your swelling started shortly after beginning a new medication or increasing a dose, that connection is worth raising with your prescriber.
Heart, Kidney, and Liver Conditions
When the heart can’t pump blood efficiently, blood flow slows and backs up in the veins returning from your legs. Fluid leaks from those congested blood vessels and collects in your ankles, lower legs, and sometimes your abdomen. This kind of swelling from heart failure typically gets worse over the course of the day and may come with shortness of breath, fatigue, or unexplained weight gain over a few days.
Kidney disease causes swelling through a different mechanism. When the kidneys can’t filter properly, sodium and water build up in the body. The swelling often shows up in both legs and may also appear around the eyes, especially in the morning. Liver disease, particularly cirrhosis, reduces the liver’s ability to produce albumin, a protein that keeps fluid inside blood vessels. When albumin levels drop, fluid leaks into the tissues more easily.
Venous insufficiency is another common cause, particularly in older adults. The valves inside your leg veins that normally prevent blood from flowing backward stop working well. Blood pools in the lower legs, leading to chronic swelling that worsens with standing and may eventually cause skin changes like darkening or thickening around the ankles.
When One Leg Swells: Blood Clots
Swelling in just one leg is a different situation from swelling in both. A deep vein thrombosis (DVT), or blood clot in a deep leg vein, is one of the most concerning causes. Along with swelling, a DVT often causes pain or cramping that starts in the calf, warmth in the affected leg, and skin that looks red or purple. The danger is that the clot can break loose and travel to the lungs.
Risk factors for DVT include recent surgery, prolonged bed rest or immobility, being over 60, and genetic clotting disorders like factor V Leiden. Long-distance travel where you’re sitting for hours also raises risk. Sometimes a DVT forms with no identifiable trigger at all. If you have sudden swelling in one leg with pain or skin color changes, that warrants urgent medical evaluation.
How to Check the Severity
A simple way to gauge your swelling is the “pitting test.” Press your thumb firmly into the swollen area for a few seconds and then release. If it leaves a dent, that’s pitting edema. How deep the dent is and how long it takes to bounce back tells you the severity:
- Grade 1 (mild): A shallow 2 mm dent that rebounds immediately
- Grade 2: A 3 to 4 mm dent that rebounds in under 15 seconds
- Grade 3: A 5 to 6 mm dent that takes 15 to 60 seconds to rebound
- Grade 4 (severe): An 8 mm dent that takes two to three minutes to fill back in
Grade 1 swelling after a long day on your feet is usually nothing to worry about. Grade 3 or 4 pitting, swelling that doesn’t resolve overnight, or swelling that’s getting progressively worse over days and weeks points toward something that needs investigation.
Reducing Swelling at Home
Elevation is the simplest and most effective first step. The key is getting your whole leg supported with your foot above hip level, not just propping your feet on a low stool. Keep your knee slightly bent rather than locked straight. Doing ankle circles and flexing your foot up and down while elevated activates the calf muscle pump, which actively pushes fluid back toward your heart.
Movement throughout the day matters more than a single elevation session. If your job involves long periods of sitting or standing, short walks or calf raises every 30 to 60 minutes can prevent fluid from pooling. Reducing sodium intake helps too, since excess salt drives your body to retain water.
Compression Stockings
Compression stockings apply graduated pressure to your legs, squeezing tightest at the ankle and gradually loosening toward the knee. They come in different pressure levels measured in mmHg:
- 15 to 20 mmHg (mild): Good for early or occasional swelling, travel prevention, or building tolerance to compression
- 20 to 30 mmHg (moderate): The most common therapeutic level, suitable for daily wear, post-injury swelling, and mild venous insufficiency
- 30 to 40 mmHg (firm): Used for more significant lower leg swelling, chronic venous insufficiency, or swelling that rebounds during the day with lighter compression
For most people with occasional swelling, 15 to 20 mmHg stockings are a reasonable starting point. If your swelling is persistent or related to a vein problem, 20 to 30 mmHg or higher is typically more effective. Stockings work best when you put them on first thing in the morning before swelling builds up during the day.
Patterns That Point to a Cause
Paying attention to the details of your swelling helps narrow down what’s behind it. Swelling in both feet that’s worse at the end of the day and goes away by morning is most often related to gravity, prolonged standing, or mild venous insufficiency. Swelling that’s present when you wake up suggests your kidneys may not be clearing fluid efficiently overnight.
Swelling that came on suddenly over a day or two is more concerning than swelling that’s been gradually building over weeks. Rapid onset in one leg with pain points toward a blood clot. Rapid onset in both legs with shortness of breath could indicate a worsening heart condition. Chronic, slowly progressive swelling in both legs with skin changes around the ankles is the classic pattern of venous insufficiency. If your swelling leaves your skin feeling tight, looks shiny, or is accompanied by new shortness of breath, chest pain, or reduced urine output, those are signs to seek medical evaluation promptly.