Common causes for swelling in the feet, ankles or legs include infection, blood clots, venous insufficiency, and heart, kidney or liver disease, according to WebMD. Other causes include sprain, fracture or other injury, as well as a reaction to certain medications.
Swelling in just one foot, ankle or leg is not typically caused by the same conditions as swelling in both legs, according to Drugs.com. It may be caused by a localized injury, or it may be due to another serious condition. If swelling in one foot is accompanied by pain, discoloration of the skin or fever, one should seek medical treatment, according to WebMD.
Blood clots can block the flow of blood through the veins, causing swelling in the ankles and feet, explains WebMD. In cases where the blood clot breaks loose and makes its way to the heart or lungs, the condition can be life-threatening. Blood thinners may be required for proper treatment. Heart, kidney or liver disease can lead to fluid buildup and water retention when the organs aren't functioning properly, which can cause swelling of the lower extremities. Many medications, such as hormone supplements, antidepressants, diabetes medications and calcium channel blockers, may cause swelling as a side effect.