Swollen feet and legs happen when fluid builds up in the tissue beneath your skin, a condition called edema. It’s extremely common and usually caused by something manageable, like sitting too long, eating salty food, or standing all day. But persistent or sudden swelling can also signal problems with your heart, kidneys, veins, or liver, so understanding the pattern of your swelling matters.
How Fluid Ends Up Trapped in Your Legs
Your body constantly moves fluid between your bloodstream and the surrounding tissue. Normally, fluid leaks out of tiny blood vessels into tissue, delivers nutrients, and then gets reabsorbed. Swelling starts when something disrupts that balance. Four basic mechanisms drive it: increased pressure inside your blood vessels pushes more fluid out, low protein levels in your blood fail to pull fluid back in, damaged or leaky vessel walls let too much fluid escape, or a blocked lymphatic system can’t drain fluid away properly.
Gravity plays a major role. When you sit or stand for hours, blood pressure in the veins of your lower legs rises, forcing more fluid into the surrounding tissue. That’s why your feet may look fine in the morning but feel tight by evening. Once swelling starts, your kidneys also respond by holding onto more sodium and water, which can make the problem snowball.
Common Everyday Causes
Most leg swelling isn’t caused by a serious illness. These are the triggers people encounter most often:
- Prolonged sitting or standing. Desk jobs, long flights, and hours on your feet all increase venous pressure in the legs.
- High sodium intake. Excess salt causes your kidneys to retain water, expanding your blood volume and pushing more fluid into tissue.
- Medications. Calcium channel blockers (commonly prescribed for blood pressure), certain diabetes drugs, steroids, and hormonal medications like estrogen or testosterone can all trigger fluid retention.
- Heat. Warm weather dilates blood vessels, which increases fluid leakage into surrounding tissue.
- Being overweight. Extra body mass increases pressure on the veins returning blood from your legs.
Organ Problems That Cause Swelling
When swelling doesn’t go away with rest and shows up alongside other symptoms, it may point to a problem with one of several major organs.
Heart Failure
When the heart can’t pump blood efficiently, blood backs up in the veins of the legs, ankles, and feet. The swelling tends to affect both legs equally and often worsens over the course of the day. You might also notice shortness of breath, especially when lying flat, or swelling in the abdomen. Fluid can even accumulate in the lungs, causing a persistent cough or difficulty breathing during exertion.
Kidney Disease
Damaged kidneys struggle to clear sodium and fluid from your blood. The resulting swelling typically shows up in the legs and around the eyes. In nephrotic syndrome, a specific type of kidney damage, the kidneys leak protein into the urine. Losing that protein reduces the blood’s ability to pull fluid back in from tissue, making swelling worse.
Liver Cirrhosis
Severe liver damage disrupts the production of albumin, the main protein that keeps fluid inside your blood vessels. Cirrhosis commonly causes fluid buildup in the abdomen (called ascites) along with swelling in the legs.
Vein and Lymphatic Problems
Two circulatory issues in the legs themselves can cause chronic swelling, and they’re often confused with each other.
Chronic venous insufficiency (CVI) happens when the one-way valves in your leg veins stop working properly. Blood pools in the lower legs instead of flowing back up to the heart. Over time, the skin may darken, feel heavy, and develop slow-healing sores. CVI is more common in people who have had blood clots, are overweight, or spend long hours standing.
Lymphedema occurs when the lymphatic system, a separate drainage network, can’t clear fluid and proteins from the tissue. It often affects one limb more than the other and produces a firmer, less “squishy” type of swelling. Lymphedema can develop after surgery or radiation that damages lymph nodes, or it can appear without a clear cause. In severe cases of CVI, the venous backup actually overwhelms the lymphatic system too, creating a combined condition called phlebolymphedema.
Swelling During Pregnancy
Some degree of ankle swelling is normal during pregnancy, especially in the third trimester. Your blood volume increases significantly, your growing uterus presses on pelvic veins, and hormonal shifts promote fluid retention. Mild puffiness in the feet and ankles that improves with rest is generally harmless.
Swelling becomes concerning when it appears suddenly in the hands, arms, or face, or when it’s accompanied by rapid weight gain. These are potential signs of preeclampsia, a serious condition marked by blood pressure at or above 140/90 mmHg and protein in the urine. Severe preeclampsia (blood pressure of 160/110 or higher) can cause intense headaches, vision changes, upper abdominal pain, or reduced urine output. Ankle swelling alone during pregnancy is not a reliable indicator of preeclampsia, but sudden facial or hand swelling with any of those other symptoms needs urgent evaluation.
When Swelling in One Leg Is a Red Flag
Swelling that affects only one leg, especially when it comes on quickly, raises the possibility of a deep vein thrombosis (DVT), a blood clot in a deep leg vein. Typical signs include pain or cramping that often starts in the calf, skin that looks red or purple over the affected area, and a feeling of warmth in that leg. DVT is more likely after surgery, during prolonged immobility (like a long flight), in people taking hormonal medications, or in those with a clotting disorder.
A DVT becomes life-threatening if the clot breaks loose and travels to the lungs, causing a pulmonary embolism. Warning signs include sudden shortness of breath, chest pain that worsens with deep breaths or coughing, a rapid pulse, dizziness or fainting, and coughing up blood. These symptoms require emergency care.
How Pitting Edema Is Assessed
If you press your thumb into a swollen area and it leaves a visible dent that slowly fills back in, that’s pitting edema. Clinicians grade it on a 1 to 4 scale based on how deep the dent is and how long it takes to rebound. A Grade 1 pit is about 2 millimeters deep and bounces back immediately. Grade 2 is 3 to 4 mm and rebounds in under 15 seconds. Grade 3 is 5 to 6 mm with rebound taking up to 60 seconds. Grade 4 leaves an 8 mm pit that can take two to three minutes to fill back in. Higher grades generally suggest more significant fluid overload and help guide how aggressively the underlying cause needs to be treated.
Not all swelling pits. Lymphedema, particularly in later stages when the tissue becomes firmer and more fibrous, often doesn’t leave a dent. If your swollen leg feels hard or “woody” rather than soft and squishy, that distinction is worth mentioning to your doctor.
Reducing Swelling at Home
For everyday, non-emergency swelling, a few consistent habits make a real difference.
Elevate your legs above your heart. Lie back and prop your legs on pillows or against a wall so they’re higher than your chest. Aim for about 15 minutes per session, three to four times a day. Gravity helps drain the pooled fluid back toward your core.
Watch your sodium. For people with heart failure, guidelines recommend limiting salt to 2,000 mg per day, with even stricter limits for moderate to severe cases. Even without heart failure, cutting back on processed foods, canned soups, and restaurant meals can noticeably reduce fluid retention. For reference, a single teaspoon of table salt contains about 2,300 mg of sodium.
Move regularly. Walking, even for short periods, activates the calf muscles that act as a pump to push blood back up through your leg veins. If you’re stuck at a desk, flexing and pointing your feet periodically helps.
How Compression Stockings Help
Compression stockings apply graduated pressure to your legs, tightest at the ankle and loosening toward the knee or thigh, which helps push fluid upward and prevents it from pooling. They come in several pressure levels measured in millimeters of mercury (mmHg):
- 15 to 20 mmHg (mild): Good for very early swelling, long flights, or building tolerance to compression. Often available without a prescription.
- 20 to 30 mmHg (moderate): The most commonly prescribed level for everyday wear with mild to moderate edema, post-surgical swelling, or early-stage lymphedema.
- 30 to 40 mmHg (firm): Used for more significant lower-leg lymphedema, chronic venous insufficiency with skin changes, or swelling that doesn’t respond to lighter compression.
- 40 to 50 mmHg and above: Reserved for severe lymphedema with hardened tissue, prescribed only after clinical assessment.
Put compression stockings on first thing in the morning before swelling has a chance to build. If they’re difficult to get on, that’s actually a sign they’re doing their job. Proper fit matters: stockings that are too loose won’t help, and ones that bunch or roll down can create a tourniquet effect that makes swelling worse.