The Uric Acid blood test, also known as kidney function test, measures the levels of uric acid in your blood. Uric acid is a waste product that is formed during the breakdown of purines, which are substances found in foods and naturally occurring in the body. Most uric acid is dissolved in the blood and excreted from the body through the kidneys in urine. Elevated levels of uric acid can be indicative of several medical conditions, most notably gout and hyperuricemia.