Swelling in the lower legs happens when fluid leaks out of your blood vessels and gets trapped in the surrounding tissue. The causes range from something as simple as sitting too long to serious conditions like heart failure or blood clots. Whether the swelling affects one leg or both, appeared suddenly or built up over weeks, tells you a lot about what’s behind it.
How Fluid Ends Up Trapped in Your Legs
Your capillaries, the smallest blood vessels, constantly filter fluid in and out of surrounding tissue. Two main forces keep this balanced: blood pressure pushing fluid out through vessel walls, and proteins in your blood (especially one called albumin) pulling fluid back in. When either side of that equation shifts, fluid accumulates in your tissue instead of staying in circulation.
Gravity makes your lower legs the most common place for this excess fluid to settle. Standing or sitting for hours increases pressure in the veins of your legs, pushing more fluid out. That’s why many people notice their ankles are puffier at the end of a long day, even without any underlying health problem. But when swelling persists, worsens, or shows up with other symptoms, something more significant is usually going on.
One Leg vs. Both Legs: Why It Matters
One of the most important clues is whether the swelling affects one leg or both. Sudden swelling in a single leg is a red flag for a deep vein thrombosis (DVT), a blood clot that forms in a deep vein, typically in the calf or thigh. DVT can cause pain, warmth, and redness in the affected leg, and it requires urgent medical evaluation because the clot can travel to the lungs.
Chronic swelling in one leg most often points to venous insufficiency or lymphedema. Both conditions develop gradually and tend to worsen over months or years.
Swelling in both legs at the same time is more likely tied to a systemic issue: heart failure, kidney disease, liver disease, medication side effects, or high salt intake. Bilateral swelling can also come from a DVT in rare cases, particularly in people with cancer.
Chronic Venous Insufficiency
This is one of the most common causes of persistent lower leg swelling. Your leg veins have one-way valves that push blood upward toward your heart. When those valves weaken or fail, blood pools in the lower legs instead of returning efficiently. The increased pressure forces fluid into the surrounding tissue.
Risk factors include obesity, pregnancy, a family history of vein problems, previous blood clots, and spending long hours sitting or standing. Smoking and lack of exercise also contribute. Beyond swelling, venous insufficiency often causes a tight feeling in the calves, itchy or painful legs, varicose veins, brownish skin discoloration near the ankles, and in advanced cases, slow-healing leg ulcers. Painful leg cramps are common too.
Diagnosis usually involves a duplex ultrasound, which checks both the structure of your leg veins and the speed and direction of blood flow through them. Treatment typically starts with compression stockings, which apply graduated pressure to help push blood back up toward the heart. Lower compression levels (under 20 mmHg) work for mild cases, while firmer compression is used for more advanced disease or DVT prevention.
Heart Failure
When the heart can’t pump blood efficiently, fluid backs up in the body. It collects most often in the lungs, legs, feet, and abdomen. Swelling in the ankles and lower legs is one of the hallmark signs of congestive heart failure, and it tends to worsen gradually over time.
Heart failure-related swelling is almost always bilateral. You might also notice shortness of breath, fatigue, and a swollen belly. New or worsening leg swelling in someone with known heart failure is a sign the condition is getting worse and needs attention.
The swelling happens partly because the weakened heart leads to reduced blood flow to the kidneys. Your kidneys respond by holding onto more sodium and water, which expands the total volume of fluid in your body and pushes even more of it into your tissues. This is why salt restriction plays a central role in managing heart failure. The Heart Failure Society of America suggests limiting sodium to 2 to 3 grams per day for most heart failure patients, with further restriction below 2 grams for moderate to severe cases.
Kidney and Liver Disease
Both your kidneys and liver play a direct role in keeping fluid where it belongs. When either organ is impaired, the balance tips toward swelling.
Your liver produces albumin, the protein responsible for pulling fluid back into your blood vessels. Liver disease, including cirrhosis, reduces albumin production, so fluid seeps out of vessels and pools in the legs and abdomen. Kidney disease can cause the same problem from the opposite direction: damaged kidneys leak albumin into the urine, depleting it from the bloodstream. Nephrotic syndrome, a specific type of kidney damage, is a well-known cause of severe leg and facial swelling for exactly this reason.
Low albumin from either cause produces a characteristic pattern of soft, pitting swelling in both legs that tends to worsen with gravity and improve overnight when you’re lying flat.
Medications That Cause Leg Swelling
Several widely prescribed drugs list lower leg swelling as a side effect. The most common culprits are calcium channel blockers, a class of blood pressure medications. These drugs widen blood vessels, which can increase the pressure that pushes fluid out of capillaries in the legs.
The effect is dose-related. At standard doses, ankle swelling occurs in roughly 1 to 15 percent of patients. At high doses taken long-term, the incidence can exceed 80 percent. Amlodipine and nifedipine are among the most frequently prescribed calcium channel blockers and among the most likely to cause this side effect, though all drugs in the class can do it.
Other medication categories that can contribute to leg swelling include certain hormone therapies, some diabetes drugs, anti-inflammatory medications like ibuprofen and naproxen, and vasodilators. If you notice new swelling after starting a medication, it’s worth raising with whoever prescribed it, since adjusting the dose or switching to a different drug often resolves the problem.
Lymphedema
Your lymphatic system acts as a drainage network, collecting excess fluid from tissues and returning it to the bloodstream. When lymph vessels or lymph nodes are damaged or blocked, fluid accumulates in the affected limb. This is lymphedema, and it most commonly affects one leg.
Common causes include surgery or radiation therapy involving pelvic or groin lymph nodes (often as part of cancer treatment), infections, and in some cases, no identifiable trigger at all. Lymphedema tends to feel firm rather than soft, and the skin may develop a textured, orange-peel appearance over time. A useful clinical marker is the Stemmer sign: if you can’t pinch and lift a fold of skin at the base of the second toe, lymphedema is likely present.
Lipedema: A Commonly Missed Cause
Lipedema is a condition involving abnormal fat deposits that accumulate symmetrically in the legs (and sometimes arms), almost exclusively in women. It’s frequently confused with simple obesity or lymphedema, but it has distinct features. The hands and feet are spared, creating a visible “cuff” where the swollen leg meets the normal-sized foot. The affected areas bruise easily, feel painful or tender to the touch, and the swelling doesn’t improve with dieting or weight loss.
Unlike the pitting edema you see with venous insufficiency or heart failure, lipedema typically produces nonpitting swelling. Pressing a finger into the skin doesn’t leave a lasting dent. Symptoms tend to worsen throughout the day, and joint hypermobility is commonly present. Because it’s underrecognized, many women go years without a correct diagnosis.
How Pitting Edema Is Graded
When a healthcare provider presses on your swollen leg and a dent remains, that’s called pitting edema. They grade it on a 1 to 4 scale based on how deep the dent is and how long it takes to bounce back:
- Grade 1: A shallow 2 mm dent that rebounds immediately
- Grade 2: A 3 to 4 mm dent that fills back in within 15 seconds
- Grade 3: A 5 to 6 mm dent that takes 15 to 60 seconds to rebound
- Grade 4: A deep 8 mm dent that lingers for two to three minutes
Higher grades generally indicate more fluid buildup and often prompt more aggressive investigation into the underlying cause.
Salt, Inactivity, and Other Everyday Factors
Not all lower leg swelling signals a disease. Excess sodium in your diet causes your kidneys to retain water, increasing the volume of fluid in your body. The American Heart Association recommends keeping sodium intake below 1,500 mg per day for the general population, though most people consume well over double that amount. Cutting back on processed and restaurant foods, which account for the majority of dietary sodium, can noticeably reduce mild swelling in people who are otherwise healthy.
Prolonged sitting, especially during long flights or desk-bound workdays, slows blood return from the legs and increases venous pressure. Pregnancy causes swelling through a combination of increased blood volume, hormonal changes that relax vessel walls, and the growing uterus compressing pelvic veins. Obesity increases venous pressure in the legs and raises the risk of venous insufficiency over time.
For everyday swelling not tied to a medical condition, elevating your legs above heart level, staying physically active, wearing compression socks during long periods of standing or travel, and reducing salt intake are the most effective strategies.