Stanozolol is a synthetic steroid that functions similarly to the naturally occurring steroid testosterone. It is used to treat hereditary angioedema, a condition that causes swelling of the face, limbs, genitals, intestinal wall, and throat. Stanozolol reduces the release of a chemical called bradykinin, which is responsible for causing the breaking and leakage of blood vessels. This damage to blood vessels leads to sudden accumulation of fluids below the skin causing swelling as well as redness. Stanozolol blocks the action of bradykinin and treats angioedema. Common side effects of Stanozolol include swelling of the legs, ankle swelling, feet swelling, and Insomnia.