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Also known as: Lactic Acid
Formal name: Lactate
Related tests: Blood gases; Pyruvate

At a Glance

Why Get Tested?

To help detect hypoxia and other diseases that cause excess production or reduced removal of lactate from the blood

When to Get Tested?

If you have symptoms such as rapid breathing, sickness, and sweating that suggest a lack of oxygen or an acid/base imbalance; if your doctor suspects that you may have an inherited metabolic or mitochondrial disorder

Sample Required?

A blood sample taken from a vein in your arm; sometimes a blood sample collected from an artery and, rarely, a sample of cerebrospinal fluid collected from the spine

Test Preparation Needed?

Fasting may or may not be required. Ask your doctor. You may also be told not to exercise for a period of time before this test.

The Test Sample

What is being tested?

This test measures the amount of lactate in the blood or, more rarely, in the cerebrospinal fluid. Lactate is the ionic (electrically charged) form of lactic acid. It is produced by muscle cells, red blood cells, brain, and other tissues during anaerobic (oxygen deficient) energy production and is usually present at low concentrations in the blood. Aerobic energy production is the body’s preferred process, but it requires an adequate supply of oxygen. Aerobic energy production occurs in the mitochondria, tiny power stations inside each cell of the body that use glucose and oxygen to produce ATP (adenosine triphosphate) which is the body’s main source of energy.

When cellular oxygen levels are low, or the mitochondria are not working properly, the body must turn to less efficient anaerobic energy production to metabolise glucose and produce ATP. In this process, the primary by-product is lactic acid, which can build up faster than the liver can break it down. When lactic acid levels increase a lot in the blood, the affected person is said to have first hyperlactataemia and then lactic acidosis (LA). The body can often compensate for the effects of hyperlactataemia, but lactic acidosis can be severe enough to disrupt a person’s acid/base (pH) balance and cause symptoms such as muscular weakness, rapid breathing, feeling sick, vomiting, sweating, and even coma.

Lactic acidosis is separated into two types: A and B. Type A is more common and may be due to inadequate oxygen uptake in the lungs and/or to decreased blood flow (hypoperfusion) resulting in decreased transport of oxygen to the tissues. The most common reason for this is shock from a variety of causes including trauma and blood loss, but LA may also be due to conditions such as heart attack, congestive heart failure, and pulmonary oedema (fluid in the lungs). Type B is caused by conditions that increase the amount of lactate/lactic acid in the blood but are not related to a decreased availability of oxygen. This includes liver and kidney disease, diabetes, leukaemia, AIDS, glycogen storage diseases (such as glucose-6-phosphatase deficiency), drugs and toxins, severe infections (both systemic sepsis and meningitis), and a variety of inherited metabolic and mitochondrial diseases (forms of muscular dystrophy that affect normal ATP production). Strenuous exercise can also result in increased blood lactate concentrations.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes, an arterial sample is collected by inserting a needle into an artery. Occasionally, a sample of cerebrospinal fluid is collected from the spinal column during a procedure called a lumbar puncture.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

Fasting may or may not be required. Ask your doctor. You may also be told not to exercise for a period of time before this test.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.