Swelling in the legs and feet happens when fluid leaks out of tiny blood vessels and gets trapped in the surrounding tissue. This can be triggered by something as simple as sitting too long or eating a salty meal, or it can signal a serious problem with your heart, kidneys, veins, or liver. The medical term is peripheral edema, and roughly 10% to 35% of U.S. adults experience some form of it. Understanding the cause matters because treatment depends entirely on what’s driving the fluid buildup.
How Fluid Ends Up in Your Tissues
Your body constantly moves fluid between your bloodstream and the tissue around it. Two forces keep this exchange balanced: pressure inside your blood vessels pushes fluid out, while proteins in your blood (mainly one called albumin) pull fluid back in. When something tips this balance, fluid accumulates in the lowest parts of your body, your legs and feet, simply because gravity pulls it there.
Three broad things can go wrong. First, pressure inside your veins can rise too high, forcing more fluid out than your body can reabsorb. Second, your blood can lose too much protein, weakening its ability to pull fluid back. Albumin levels below about 2 grams per deciliter almost always produce visible swelling. Third, your lymphatic system, the network of tiny channels that drains excess fluid from tissues, can become blocked or damaged. Most causes of leg swelling fall into one of these three categories.
Venous Insufficiency: The Most Common Cause
Chronic venous insufficiency (CVI) is the single most frequent reason for persistent leg swelling, affecting up to 17% of men and 40% of women. Inside your leg veins, small one-way valves keep blood flowing upward toward your heart. When these valves weaken or widen, blood pools in the lower legs, raising pressure in the veins and pushing fluid into surrounding tissue.
Valve damage often follows a blood clot. A past deep vein thrombosis causes inflammation and scarring inside the vein, leaving the valves stiff and unable to close properly. But valves can also fail simply from age, obesity, or years of standing for work. The progression tends to follow a pattern: first, visible varicose veins; then daily swelling that worsens through the day and improves overnight; eventually, skin changes like darkening or thickening around the ankles. About 1% to 3% of people with CVI develop open sores (venous ulcers) on the lower legs, a rate that climbs to 4% in adults over 65.
Heart Failure and Fluid Retention
When the heart can’t pump blood efficiently, the backup affects the entire body. Blood pools in the veins, raising pressure and pushing fluid into tissues. But the swelling in heart failure isn’t just a plumbing problem. It also involves a hormonal chain reaction.
As the heart’s output drops, your kidneys sense reduced blood flow and respond by retaining sodium and water to try to boost blood volume. Stress hormones tighten blood vessels, raising pressure further. The kidneys also get squeezed by rising pressure in the abdomen and in the veins draining them, which further reduces their ability to filter and excrete fluid. The result is a self-reinforcing cycle: the body holds onto more and more fluid, and the legs and feet bear the brunt. Swelling from heart failure typically affects both legs equally, worsens as the day goes on, and may be accompanied by shortness of breath, fatigue, or rapid weight gain over a few days.
Kidney and Liver Disease
Your kidneys and liver both play direct roles in fluid balance, and disease in either organ produces swelling through different pathways.
Kidney disease, particularly a condition called nephrotic syndrome, causes your kidneys to dump large amounts of protein into your urine. As albumin levels in the blood drop, there’s less force pulling fluid back into your bloodstream, so it leaks into tissues. Kidney disease can also impair your body’s ability to excrete sodium, compounding the problem.
Advanced liver disease (cirrhosis) disrupts fluid balance from two directions. The liver manufactures albumin, so a damaged liver produces less of it, weakening the blood’s ability to hold onto fluid. At the same time, scarring in the liver blocks blood flow through the organ, raising pressure in the veins that drain the abdomen and legs. This combination often produces swelling in the legs alongside a fluid-filled, distended belly.
Medications That Cause Swelling
Several widely prescribed medications list leg swelling as a common side effect. If your swelling started or worsened after beginning a new drug, the medication itself may be the cause.
- Blood pressure medications (calcium channel blockers): These are the most frequent culprits. They relax arteries more than veins, which raises pressure inside the smallest blood vessels and forces fluid out. About 25% of people taking these drugs develop peripheral edema, and a quarter of those stop the medication because of it.
- Anti-inflammatory painkillers (NSAIDs): Ibuprofen, naproxen, and similar drugs reduce blood flow to the kidneys and trigger sodium and water retention. Both older NSAIDs and newer selective types cause edema at similar rates.
- Nerve pain medications: Gabapentin and pregabalin can cause swelling through a mechanism similar to calcium channel blockers.
- Diabetes medications (thiazolidinediones): These increase swelling risk in 3% to 5% of people when used alone, but the rate jumps to 13% to 16% when combined with insulin.
- Other drugs: Dopamine agonists used for Parkinson’s disease, certain antipsychotics, and nitrate medications for chest pain can all contribute to leg swelling by reducing the force that moves blood forward through the veins.
Deep Vein Thrombosis: When One Leg Swells
Swelling that appears suddenly in just one leg deserves urgent attention. A blood clot in a deep leg vein (DVT) blocks blood from draining properly, causing rapid swelling, pain, warmth, and sometimes a bluish discoloration. The swelling may be limited to below the knee or extend all the way up to the groin, depending on where the clot sits.
Your risk is higher if you’ve recently been immobilized for more than three days, had surgery in the past 12 weeks, have active cancer, or are on bed rest. A classic warning sign is a calf that measures more than 3 centimeters larger than the other leg, combined with pitting edema (where pressing a finger into the skin leaves an indent) only on the swollen side. DVT is dangerous because pieces of the clot can break off and travel to the lungs, so sudden one-sided leg swelling warrants same-day medical evaluation.
Lymphedema
When the lymphatic drainage system is damaged or blocked, protein-rich fluid builds up in the tissues. This produces a distinctive type of swelling that feels firmer than typical edema and doesn’t fully resolve with elevation. Lymphedema most commonly develops after cancer treatment that involves removing or radiating lymph nodes, but it can also be inherited or result from infection.
One way to distinguish lymphedema from other types of swelling is a simple skin test. Try to pinch the skin on top of your second toe between your fingers. If the skin is too thick and tight to pinch, this is considered a positive Stemmer’s sign, which is present in about 92% of lymphedema cases. Unlike other forms of edema, lymphedema tends to worsen over time if untreated because the accumulated protein triggers inflammation and tissue thickening.
Pregnancy and Preeclampsia
Mild leg and foot swelling is normal during pregnancy, especially in the third trimester, as the growing uterus puts pressure on pelvic veins and blood volume increases by nearly 50%. This type of swelling tends to come on gradually and affects both feet.
What isn’t normal is sudden swelling of the face, hands, or feet. This can be a sign of preeclampsia, a serious pregnancy complication involving high blood pressure and organ stress. Sudden swelling during pregnancy, particularly when paired with headaches, vision changes, or upper abdominal pain, needs immediate medical evaluation.
Salt Intake and Prolonged Sitting
Not all leg swelling points to disease. Two of the most common triggers are dietary sodium and simple gravity. Research in older adults has shown that daily salt intake directly correlates with the amount of leg swelling measured by evening. The more sodium you consume, the more water your body retains, and that fluid settles in your lower legs throughout the day.
Similarly, sitting or standing in one position for hours, whether on a long flight, at a desk, or during a shift on your feet, lets gravity pull fluid downward. Without the pumping action of walking, your calf muscles can’t push blood back up through the veins efficiently. This type of swelling is usually mild, affects both legs, and resolves after you elevate your feet or walk around.
Pitting Edema: What the Severity Means
When you press a finger into swollen skin and it leaves a dent that slowly fills back in, that’s pitting edema. Clinicians grade it on a scale based on how deep the indent goes: less than 4 millimeters is grade 1 (mild), 4 to 6 millimeters is grade 2, 6 to 8 millimeters is grade 3, and anything deeper than 8 millimeters is grade 4 (severe). Higher grades generally indicate more fluid accumulation and a greater likelihood that a systemic cause, like heart, kidney, or liver disease, is involved rather than a local vein problem.
Managing Swelling at Home
For mild, non-urgent swelling, a few strategies can help move fluid out of the legs. Elevating your feet above heart level for 20 to 30 minutes several times a day uses gravity in your favor. Reducing sodium intake lowers the amount of water your body holds onto. Regular walking activates the calf muscles, which act as a pump to push blood upward through the veins.
Compression stockings provide steady external pressure that counteracts fluid leakage. For everyday swelling related to prolonged sitting or standing, stockings rated 15 to 20 mmHg are effective and available without a prescription. Stockings in the 20 to 30 mmHg range provide stronger compression and are more effective for people with chronic venous insufficiency, though they can be harder to put on. Research shows both pressure levels significantly reduce leg volume compared to no compression, with the higher range performing slightly better for people who sit for long periods. If your swelling is caused by a medication, the fix may be as straightforward as switching to an alternative drug.