What should you know about left lower leg swelling?

Swelling happens when fluid collects in tissues. Varicose veins can slow blood returning from the leg, especially after standing. A sprain, muscle strain, insect bite, or skin infection can affect one side. Heart or kidney conditions can also cause fluid retention, although they often produce swelling in both legs. A clot in a deep vein is another possibility and may cause swelling, warmth, tenderness, or a heavy feeling; it cannot be confirmed from appearance alone.

Arrange prompt clinical advice for swelling that is new, worsening, painful, warm, or unexplained. Note when it began, whether the skin changed colour, and whether recent travel, reduced movement, surgery, injury, or new medicines preceded it. Until assessed, avoid massage of a suddenly swollen leg. Gentle movement may be suitable for some people, but follow individual advice. A clinician may compare both legs, check circulation, and decide whether imaging or blood tests are needed.

Seek emergency help for swelling with sudden breathlessness, chest pain, coughing blood, faintness, or a fast or irregular heartbeat. Seek same-day care if the leg is rapidly enlarging, very painful, hot and red, or if you have fever or feel acutely unwell. These features need assessment for problems affecting the leg or lungs.

Ask whether the pattern suggests a vein problem, infection, injury, or fluid retention; whether you need an ultrasound; which activities are safe while waiting; and which changes should trigger urgent review.