Test Overview

A lactic acid (also called lactate) test is a blood test that measures the level of lactic acid made in the body. Most of it is made by muscle tissue and red blood cells. When the oxygen level in the body is normal, carbohydrate breaks down into water and carbon dioxide. When the oxygen level is low, carbohydrate breaks down for energy and makes lactic acid.

Lactic acid levels get higher when strenuous exercise or other conditions—such as heart failure, a severe infection (sepsis), or shock—lower the flow of blood and oxygen throughout the body. Lactic acid levels can also get higher 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. Lactic acidosis can also occur in a person who takes metformin (Glucophage) to control diabetes when heart or kidney failure or a severe infection is also present.

A lactic acid test is generally done on a blood sample taken from a vein in the arm but it may also be done on a sample of blood taken from an artery (arterial blood gas).

Why It Is Done

A test for lactic acid is done to:

• Check for lactic acidosis. Symptoms of lactic acidosis include rapid breathing, excessive sweating, cool and clammy skin, sweet-smelling breath, belly pain, nausea or vomiting, confusion, and coma.
• See whether the right amount of oxygen is reaching the body's tissues.
• Find the cause for a high amount of acid (low pH) in the blood.

How To Prepare

To prepare for a lactic acid test:

• Do not eat or drink anything other than water for 8 to 10 hours before the test.
• Do not exercise for several hours before the test. Do not clench your fist while having your blood drawn for a lactic acid test. These activities may change the results.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

Watch

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

High values

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

• Severe loss of water from the blood (dehydration).
• Blood problems, such as severe anemia or leukemia.
• Liver disease or liver damage that prevents the liver 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, carbon monoxide poisoning, or pulmonary embolism that prevent adequate oxygen from reaching the body's cells.
• Extremely strenuous exercise or extreme overheating.
• Poisoning by alcohol (ethanol), wood alcohol (methanol), or antifreeze (ethylene glycol).
• Some medicines, such as isoniazid for tuberculosis or metformin (Glucophage) for diabetes. Lactic acidosis is a concern for people who take metformin to control their diabetes, especially if they have poor kidney function.