One of the most common causes of swollen legs is venous insufficiency, where weakened veins struggle to return blood to the heart efficiently. This leads to fluid leakage into surrounding tissues. Similarly, deep vein thrombosis (DVT), a blood clot in the leg, can cause sudden, often painful swelling and requires immediate medical attention. Other circulatory issues, such as lymphedema (a blockage in the lymphatic system), can also contribute to chronic swelling.

Heart, kidney, or liver disease can lead to fluid retention throughout the body, often noticeable in the legs and ankles. For example, congestive heart failure reduces the heart’s pumping efficiency, causing blood to back up in the veins and fluid to seep into tissues. Kidney disease impairs the body’s ability to remove excess fluid and waste, while liver disease can disrupt protein production, leading to fluid accumulation. Hormonal changes during pregnancy or due to certain medications (like blood pressure drugs or steroids) may also trigger swelling.

While mild swelling can often be managed with lifestyle changes—such as elevating the legs, wearing compression stockings, and reducing salt intake—persistent or severe swelling should never be ignored. If swelling is sudden, one-sided, or accompanied by pain, redness, or difficulty breathing, seek medical help immediately, as it could indicate a serious condition like a blood clot or heart failure. Early diagnosis and treatment are key to preventing complications.