What does swelling in one leg mean?

One leg swollen while the other stays normal is a pattern that deserves same-day attention, because the cause you must rule out first is a deep vein thrombosis - a blood clot in a leg vein. MedlinePlus lists the DVT pattern: swelling in one leg, often the calf, with pain or tenderness, warmth, and sometimes reddish or bluish skin. Risk factors include recent surgery, long flights or car rides, birth control pills or pregnancy, cancer, and a family history of clots. Why the urgency: a piece of the clot can travel to the lungs - a pulmonary embolism. If one-sided swelling comes with sudden shortness of breath, chest pain that worsens with breathing, a racing heart, or coughing blood, call emergency services. That combination is life-threatening and very treatable when caught. The friendlier causes exist too: a recent twist or strain of that leg, a varicose vein flare, a knee that swells and leaks fluid downward, or a skin infection like cellulitis - which brings spreading redness, warmth, and fever. But because you cannot reliably tell these from a clot at home, new one-sided swelling means call today. The test is a painless ultrasound and it is quick. Pymander is a free AI doctor, 24/7 by text. It can walk you through the clot risk factors and help you decide how fast to move.