Lactic acid is mainly produced in muscle cells and red blood cells. It forms when the body breaks down carbohydrates to use for energy during times of low oxygen levels. Your body's oxygen level might drop during intense exercise or if you have an infection or disease.

A test can be done to measure the amount of lactic acid in the blood.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

Do not exercise for several hours before the test. Exercise can cause a temporary increase in lactic acid levels.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

This test is usually done to diagnose lactic acidosis.

4.5 to 19.8 mg/dL (0.5-2.2 mmol/L)

Note: mg/dL = milligrams per deciliter; mmol/L = millimoles per liter

Abnormal results suggest that body tissues are not getting enough oxygen. See: Oxygen deprivation

Conditions associated with increased lactic acid levels include:

• Hypoxia seen in shock
• Congestive heart failure
• Hepatic (liver) problems
• Ischemia (not enough oxygenated blood getting to a certain area)
• Lung disease

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Risks may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Clenching the fist or having the elastic band in place for a long time while having blood drawn can artificially increase lactic acid level.