What can cause water in the legs and swelling?

People often call this water retention; clinicians may call it oedema. It can leave sock marks, make the skin feel tight, or cause an indentation after gentle pressure. Swelling in both legs after prolonged standing may relate to sluggish vein return, including varicose veins. One-sided swelling can have a different cause. Heart failure and chronic kidney disease can lead to fluid accumulation, while reduced movement and obesity may increase pressure on the legs. The timing, symmetry, skin colour, breathlessness, and change in urination are useful clues.

Move your ankles and walk gently if safe; avoid sitting or standing in one position for long periods. Elevate the legs when resting, choose comfortable footwear, and protect swollen skin from cracks or infection. Do not start water tablets, restrict fluids, or use tight compression garments without advice, because the right approach depends on the cause and circulation. Record when swelling appears and whether it improves overnight.

Seek emergency help for swelling with sudden breathlessness, chest pain, fainting, or coughing blood. Obtain prompt assessment for new one-sided swelling with pain, warmth, or redness; rapidly increasing swelling; severe skin pain; or a marked reduction in urination. Arrange a medical review for persistent swelling, weight change, breathlessness when lying down, or swelling that does not improve with rest.

Is the swelling related to veins, medicines, the heart, or the kidneys? Do I need blood or urine tests? Is compression suitable for my circulation? What changes in salt, activity, or fluids are safe for me?