What To Think About

• Results from a lactic acid test may be more accurate when the blood is taken from an artery (arterial blood gas) rather than from a vein. For more information, see the topic Arterial Blood Gas.
• During aerobic exercise, the heart and lungs supply adequate amounts of oxygen to the body for energy. Anaerobic exercise uses more oxygen than the lungs and heart can supply to the body so the energy supply is less, thus causing high lactic acid levels in the blood. Usually anaerobic exercise forces a person to slow down or stop exercising because lactic acid buildup causes moderate to severe muscle aches and muscle stiffness. But some highly trained athletes learn to tolerate short periods of high lactic acid levels. During aerobic exercise, the air you breathe contains enough oxygen to use blood sugars normally and completely for the body's energy needs, and lactic acid levels do not rise.
• Lactic acid can be measured in fluids other than blood, such as spinal fluid. Lactic acid levels in body fluids often increase when an infection is present. The amount of lactic acid in spinal fluid may be measured to determine whether a brain infection is being caused by bacteria or a virus.