Swollen feet happen when fluid builds up in the tissues of your lower extremities, a condition called edema. The causes range from something as simple as sitting too long to serious conditions like heart failure or a blood clot. Whether one foot or both are swollen, and how quickly the swelling appeared, tells you a lot about what’s going on.
Both Feet Swollen: Common Causes
When both feet swell at the same time, the cause is usually something affecting your whole body rather than a localized injury. Gravity pulls fluid downward throughout the day, so your feet and ankles are the first place excess fluid shows up.
The most straightforward triggers are lifestyle-related. Standing or sitting for long stretches, especially during travel, lets fluid pool in your lower legs. Eating a lot of salty food causes your body to hold onto extra water. Hot weather dilates blood vessels and makes it easier for fluid to seep into surrounding tissue. Many common medications also cause foot swelling as a side effect, including blood pressure drugs called calcium channel blockers, certain diabetes medications, anti-inflammatory painkillers like ibuprofen, and some antidepressants.
More serious systemic causes include:
- Heart failure: When the heart can’t pump efficiently, blood backs up in the veins of your legs, ankles, and feet. Swelling that worsens throughout the day and improves overnight is a hallmark pattern.
- Kidney disease: Your kidneys normally filter excess fluid and salt from your blood. When they’re damaged, that fluid accumulates, typically showing up in the legs and around the eyes.
- Liver cirrhosis: Severe liver damage disrupts the production of proteins that keep fluid inside your blood vessels, allowing it to leak into your abdomen and legs.
- Venous insufficiency: The valves inside your leg veins weaken over time and stop pushing blood back up toward your heart efficiently. Blood pools in the lower legs, and over months or years, you may notice varicose veins, skin discoloration, thickening skin around the ankles, and slow-healing wounds on the lower legs.
One Foot Swollen: Why It Matters
Swelling in just one foot or leg deserves closer attention because it can signal a blood clot. Deep vein thrombosis (DVT) occurs when a clot forms in one of the large veins of the leg. Along with swelling, you may notice pain or cramping that starts in the calf, a feeling of warmth in the affected leg, and skin that turns red or purple. Some people with DVT have no noticeable symptoms at all, which is part of what makes it dangerous.
Your risk for DVT goes up after surgery, prolonged bed rest, a long flight, or any injury to the leg. If a clot breaks free and travels to the lungs, it becomes a pulmonary embolism, which is life-threatening.
Other causes of one-sided swelling include a sprained ankle, a broken bone, an infection in the foot or leg, or a blocked lymph node on that side of the body.
Swollen Feet During Pregnancy
Some foot swelling during pregnancy is completely normal, particularly in the third trimester. Your body retains more fluid, your growing uterus puts pressure on the veins returning blood from your legs, and the increased blood volume all contribute.
The concern is preeclampsia, a pregnancy complication that involves high blood pressure (above 140/90 mmHg) and signs of kidney stress, including protein in the urine. Swelling from preeclampsia tends to come on suddenly and often affects the hands and face in addition to the feet and ankles. Rapid weight gain over a few days, severe headaches, vision changes, or pain under the ribs on the right side are all warning signs that need immediate medical evaluation.
How Doctors Evaluate Swelling
One of the first things a provider does is press a finger into the swollen area for several seconds and watch what happens. If the pressure leaves a visible dent that slowly fills back in, that’s called pitting edema, and the depth of the pit helps grade the severity. A shallow 2-millimeter dent that rebounds immediately is grade 1. At the other end, a deep 8-millimeter pit that takes two to three minutes to refill is grade 4. This grading helps track whether swelling is getting better or worse over time.
Beyond the physical exam, your doctor may order blood work to check kidney and liver function, a urine test to look for protein loss, an ultrasound to evaluate blood flow in your leg veins or to check heart function, or a chest X-ray if heart failure is suspected. The combination of where the swelling is, how quickly it developed, and what other symptoms are present guides which tests make sense.
Reducing Swelling at Home
Elevation is the simplest and most effective immediate step. Prop your feet above the level of your heart for 15 to 20 minutes several times a day. Doing this while you sleep (by placing a pillow under your calves) can help the fluid drain overnight. Movement matters too: flexing your ankles, going for short walks, and avoiding long periods of sitting or standing all help your calf muscles pump fluid back up toward your heart.
Salt plays a direct role in fluid retention. For people dealing with persistent edema, keeping daily sodium intake between roughly 1,400 and 1,800 milligrams can make a noticeable difference. That’s significantly less than the average intake, which hovers around 3,400 milligrams per day for most adults. Reading labels and cutting back on processed foods, canned soups, deli meats, and restaurant meals are the fastest ways to lower your sodium.
Compression stockings apply steady pressure to your lower legs and prevent fluid from settling into the tissues. For mild swelling, stockings rated at 15 to 20 mmHg of pressure are usually enough. Moderate swelling or early venous insufficiency typically calls for 20 to 30 mmHg. Stockings in the 30 to 40 mmHg range are used for more stubborn swelling, significant varicose veins, or after treatment for lymphedema. Anything above 40 mmHg should only be worn after a clinical assessment. Put compression stockings on first thing in the morning before swelling builds up during the day.
When Swollen Feet Are an Emergency
Most foot swelling is not an emergency, but certain combinations of symptoms require immediate help. Call 911 if swollen feet are accompanied by chest pain, difficulty breathing, shortness of breath when lying flat, dizziness or fainting, or coughing up blood. These can indicate a blood clot in the lungs or acute heart failure.
Get urgent care if the swelling appears suddenly with no obvious cause, follows a physical injury like a fall or car accident, or occurs in only one leg with pain, pale skin, or coolness to the touch. Sudden one-sided swelling is the pattern most associated with DVT, and early treatment prevents the clot from becoming more dangerous.