A swollen foot is almost always caused by fluid collecting in the tissue, and the reason ranges from something as simple as standing too long to something as serious as a blood clot or heart problem. The key first question is whether one foot is swollen or both, because that distinction points toward very different causes.
One Swollen Foot vs. Both
When only one foot swells, the cause is usually local: an injury, an infection, or a problem with blood flow in that specific leg. About 40% of sudden one-sided leg swelling traces back to a muscle strain, tear, or twisting injury. Another 7% comes from problems with lymph drainage or vein function, and about 3% from skin infections like cellulitis. In roughly a quarter of cases, no clear cause is ever identified.
When both feet swell, the cause is more likely systemic, meaning something affecting your whole body. Chronic vein disease is the most common culprit, but heart failure, kidney disease, liver disease, and certain medications all cause fluid to accumulate in both lower extremities. Hormonal shifts, including the normal changes of a menstrual cycle or pregnancy, can also cause bilateral swelling.
Injuries and Sprains
If your foot swelled after you twisted it, dropped something on it, or started a new physical activity, inflammation from tissue damage is the most likely explanation. The body floods the injured area with fluid as part of its healing response, and swelling after a sprain or soft tissue injury can persist far longer than most people expect. You may notice improvement within the first few weeks, but residual swelling and stiffness can linger for 6 to 12 months as you return to normal activity. If you still have significant pain and swelling after six weeks, that warrants medical evaluation to rule out a fracture or more serious ligament damage.
Vein Problems
Your leg veins contain one-way valves that push blood upward toward your heart against gravity. When those valves become damaged, blood flows backward and pools in your lower legs, a condition called chronic venous insufficiency. This is the single most common cause of long-term foot and ankle swelling. Over time, the increased pressure forces fluid out of your veins and into surrounding tissue. In severe cases, this trapped fluid causes scar tissue to form, which locks even more fluid in place and makes the swelling progressively harder to reverse.
Signs that your swelling is vein-related include skin that looks darker or brownish around the ankles, visible varicose veins, a heavy or achy feeling in your legs that worsens through the day, and in advanced cases, open sores or ulcers near the ankle. A history of blood clots raises your risk significantly.
Medications That Cause Swelling
Several common prescription drugs cause foot swelling as a side effect, and many people don’t make the connection. Calcium channel blockers used for blood pressure are among the worst offenders. Amlodipine, one of the most widely prescribed blood pressure drugs in the world, causes noticeable ankle and foot swelling in nearly half the people who take it.
Other medications linked to foot swelling include:
- Other blood pressure drugs: beta blockers, clonidine, hydralazine, minoxidil
- Hormone therapies: corticosteroids (like prednisone), estrogen, progesterone, testosterone
- Nerve pain and seizure drugs: gabapentin and pregabalin
- NSAIDs: ibuprofen, naproxen, and similar anti-inflammatory painkillers
- The diabetes drug pioglitazone
- Certain antidepressants (MAOIs)
If your swelling started within weeks of beginning a new medication, that timing is worth mentioning to whoever prescribed it. Switching to a different drug in the same class often resolves the problem.
Heart, Kidney, and Liver Disease
Swelling in both feet that develops gradually and worsens over weeks can signal an organ that isn’t working properly. In heart failure, the heart pumps blood too slowly, which causes it to back up in the veins returning from your legs. Fluid leaks out of those congested blood vessels and settles into your tissues. You’d typically also notice shortness of breath (especially when lying flat), unusual fatigue, or a swollen belly.
Kidney disease causes swelling through a different mechanism: the kidneys fail to filter enough fluid and salt from your blood, so your total fluid volume rises and gravity pulls the excess into your feet and ankles. Liver disease, particularly cirrhosis, reduces production of a key blood protein that holds fluid inside your vessels. Without enough of that protein, fluid seeps into tissues throughout the body, often showing up first in the feet and abdomen.
Swelling During Pregnancy
Some degree of foot and ankle swelling is normal during pregnancy, especially in the third trimester. Your body retains more fluid, your blood volume increases, and the growing uterus puts pressure on the veins returning blood from your legs.
What isn’t normal is sudden, significant swelling of your hands, arms, or face, particularly if accompanied by headaches, vision changes, or upper abdominal pain. These are hallmarks of preeclampsia, a serious pregnancy complication involving high blood pressure. The key distinction: gradual ankle puffiness that comes and goes is expected, while rapid swelling above the ankles with unexpected weight gain from fluid retention needs prompt medical attention.
When Swelling Is an Emergency
A blood clot in a deep vein, known as DVT, is the most dangerous cause of sudden one-sided foot or leg swelling. Along with swelling, DVT typically causes pain or tenderness that may only appear when you stand or walk, warmth in the swollen area, and skin that looks red or discolored. Some people have no symptoms at all until the clot breaks loose and travels to the lungs, causing chest pain, shortness of breath, coughing up blood, or fainting. That complication, a pulmonary embolism, is life-threatening. If you have sudden one-sided leg swelling with warmth and pain, or any combination of chest pain and difficulty breathing, seek emergency care immediately rather than waiting to see if it improves.
How Doctors Assess Swelling
One of the first things a provider will do is press a finger into the swollen area for several seconds, then release. If the pressure leaves a visible dent that takes time to bounce back, that’s called pitting edema, and the depth of the dent helps gauge severity. A shallow 2-millimeter pit that rebounds instantly is Grade 1, the mildest form. An 8-millimeter pit that takes two to three minutes to fill back in is Grade 4, indicating significant fluid accumulation. This simple test, combined with whether the swelling is in one leg or both and how quickly it developed, helps narrow the list of possible causes before any imaging or bloodwork.
Reducing Swelling at Home
For swelling caused by minor injuries, prolonged standing, or mild fluid retention, elevation is the single most effective thing you can do. Prop your foot up at or above heart level whenever you’re sitting or lying down. This means reclining with your leg on a stack of pillows, not just resting it on an ottoman while sitting upright in a chair. Gravity is working against you all day, and you need to reverse that angle meaningfully.
Ice helps in the first 48 to 72 hours after an injury by constricting blood vessels and limiting inflammatory fluid. Apply it for 15 to 20 minutes at a time with a layer of fabric between the ice and your skin. Compression socks or stockings help with vein-related swelling by physically squeezing fluid back up toward your heart. Reducing salt intake matters if your swelling is related to fluid retention from medications, hormonal changes, or early organ problems, since sodium causes your body to hold onto water.
Movement also helps. Your calf muscles act as a pump that pushes blood upward through your veins. Sitting or standing still for hours disables that pump. Even simple ankle circles or short walks throughout the day can make a noticeable difference for people whose swelling worsens with inactivity.