Lactate

Alternative names
Lactic acid

Definition
This is a blood test that measures the amount of lactic acid.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test
Do not exercise for several hours before the test.

Infants and children:
The preparation you can provide for this test depends on your child’s age and previous experience. For specific information regarding how you can prepare your child, see the following topics:

     
  • infant test or procedure preparation (birth to 1 year)  
  • toddler test or procedure preparation (1 to 3 years)  
  • preschooler test or procedure preparation (3 to 6 years)  
  • schoolage test or procedure preparation (6 to 12 years)  
  • adolescent test or procedure preparation (12 to 18 years)

How the test will feel
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.

Why the test is performed

This test is usually used to see if lactic acid accumulation is causing acidosis (acidotic body state) symptoms.

Lactic acid is an intermediate product of carbohydrate metabolism and is derived mainly from muscle cells and red blood cells. During exercise, lactate levels may increase. However, the liver can normally metabolize more lactate than is produced and can return lactate levels to normal within a few hours.

Normal Values
4.5 to 19.8 mg/dl (0.5-2.2 mmol/L)

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

What abnormal results mean

Severe oxygen deprivation of tissues results in a switch from aerobic to anaerobic metabolism. Because lactate is the main product of anaerobic metabolism, it accumulates when there is oxygen deprivation.

Hypoxia seen in shock, congestive heart failure (or any other condition that would cause problems in oxygen being picked up by or transported in the blood), hepatic (liver) dysfunction, ischemia (not enough oxygenated blood getting to a certain area), and pulmonary (lung) insufficiency are all associated with increased serum lactate.

What the risks are

     
  • excessive bleeding  
  • fainting or feeling light-headed  
  • hematoma (blood accumulating under the skin)  
  • infection (a slight risk any time the skin is broken)  
  • multiple punctures to locate veins

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

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.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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