A lactic acid 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
The health professional drawing blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein. An elastic band may not be used for a lactic acid test because a band around the arm muscle may cause a false increase in lactic acid.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure on the site and then put on a bandage.