At a glance
Also known as
Why get tested?
To help detect hypoxia (oxygen deficiency) and other conditions that cause excess production or insufficient clearing of lactate from the blood
When to get tested?
The test is usually requested in emergency departments and intensive care units for patients with severe infection, sepsis, shock in and other clinical situations that suggest a lack of oxygen or an . It is sometimes requested if it is suspected someone may have an inherited metabolic or mitochondrial disorder or in situations where there is the possibility of drug side effects.
A blood sample drawn from a vein in the arm; sometimes a blood sample collected from an artery and, rarely, a sample of (CSF) is collected from the lumbar region of the spinal canal.
Test preparation needed?
may be required. Your doctor will advise you. You may also be told to not do any exercise before the sample is collected.
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 energy production, that is energy production by breaking down foods without using any oxygen in the process. Lactate is usually present in low levels in the blood. Aerobic energy production is the body’s preferred process, that is production of energy by combining foods with oxygen but it requires an adequate supply of oxygen. Aerobic energy production occurs in the , tiny power stations inside each cell of the body that use glucose and oxygen to produce ATP (adenosine triphosphate), the body’s primary source of energy.
When cellular oxygen levels are decreased or the mitochondria are not functioning properly such as in some rare inherited disorders, the body must turn to less efficient anaerobic energy production to metabolise glucose and produce ATP. In this process, the primary byproduct is lactic acid which can build up faster than the liver can break it down. When lactic acid levels increase significantly in the blood, someone is said to have hyperlactataemia which can then progress to become lactic acidosis as more lactic acid accumulates. The body can often compensate for the effects of hyperlactataemia but lactic acidosis can be severe enough to disrupt a person’s and cause symptoms such as muscular weakness, rapid breathing, nausea, vomiting, sweating and even coma.
Lactic acidosis is classified in two groups - types A and B.
- Type A lactic acidosis, the most common type, may be due to conditions that cause someone to be unable to breathe in enough oxygen (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. However, lactic acidosis may also be due to conditions such as heart attack, congestive heart failure and pulmonary oedema (fluid in the lungs).
- Type B lactic acidosis is not related to delivery of oxygen but reflects excess demand for oxygen or metabolic problems. This includes liver and kidney disease, uncontrolled diabetes, leukaemia, AIDS, storage diseases (such as glucose-6-phosphatase deficiency), drugs and toxins, severe infections (both systemic and ) 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 levels of lactate.
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 is collected from the spinal canal during a procedure called a .
Is any test preparation needed to ensure the quality of the sample?
Your doctor will let you know if you need to . You may also be told not to exercise for a period of time before this test.