Lactic acid is produced mainly by muscle tissue and red blood cells. It is a waste product formed when oxygen levels in the body are low and the body breaks down sugars (carbohydrates) for energy.

When plenty of oxygen is available to the body's cells, carbohydrates break down into water and carbon dioxide. However, when oxygen is scarce, carbohydrates break down into lactic acid. Therefore, the amount of lactic acid in the blood depends on how much oxygen is available to the body.

Lactic acid levels increase when strenuous exercise or other conditions (such as heart failure, a severe infection, or shock) reduce the flow of blood and delivery of oxygen throughout the body. Lactic acid levels can also increase when the liver is severely damaged or diseased, because the liver normally breaks down lactic acid.

Very high levels of lactic acid cause a serious, sometimes life-threatening condition called lactic acidosis. This condition can occur when the body's tissues do not get enough oxygen and can be caused by shock or a severe infection.

This test is usually done on a blood sample taken from a vein. However, it is sometimes done on a sample of blood taken from an artery.

Lactic Acid
Results

Normal

Normal values may vary from lab to lab.

Greater than normal values may mean

A high lactic acid value indicates lactic acidosis, which can be caused by:

• Severe loss of water from the blood (dehydration).
• Blood problems, such as severe anemia or leukemia.
• Damage or disease of the liver that prevents it from breaking down lactic acid in the blood.
• Conditions (such as severe bleeding, shock, severe infection, heart failure, blockage of blood flow to the intestines, or pulmonary embolism) that prevent enough oxygen from reaching the body's cells.
• Extremely strenuous exercise or extreme overheating.
• Poisoning by alcohol (ethanol), wood alcohol (methanol), antifreeze (ethylene glycol), or taking an overdose of acetaminophen (the active ingredient in Tylenol).
• The use of some medications, such as metformin (Glucophage) for diabetes or isoniazid for tuberculosis.