Lactate Test
Reviewed
Also called: Lactic Acid Test, Lactic Acid: Plasma, L-Lactate
This test measures the level of lactate, also called lactic acid, in a sample of your blood. In certain cases, cerebrospinal fluid (CSF) may be used.
Specimen: Blood (vein or artery) or cerebrospinal fluid (CSF)
Why this test may be ordered
- To check for symptoms of lactic acidosis, such as shortness of breath, nausea, vomiting, muscle weakness, sweating, or abdominal pain
- To find out if your cells are getting enough oxygen
- To help determine why you have too much acid in your blood
- To help evaluate and monitor conditions that may raise lactate levels
- To help distinguish bacterial meningitis from viral meningitis when meningitis is suspected
Preparation and collection
Your provider will tell you how to prepare for your test. Your provider may tell you to: Avoid exercise for several hours before the test. That's because exercise can cause a temporary increase in lactate levels. Fast (not eat or drink) for 8 to 10 hours before the test. You may need to stop taking certain medicines before this test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.
A health care professional will take a blood sample from a vein or an artery. Make sure you don't clench your fist during the test, as this can temporarily raise lactate levels. A blood sample taken from an artery tends to be more uncomfortable than most blood tests, which use a vein. Pressure will be applied to the site for at least 5 minutes to stop the bleeding.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly. After a blood test from an artery, you may have some bleeding, bruising, or soreness at the spot where the needle was put in. Very rarely, the needle may damage a nerve or the artery. You may be told to avoid lifting heavy objects for 24 hours after the test.
Understanding results
If a result or symptoms suggest an emergency, get emergency medical help right away.
The results of a lactate test can only show whether you have abnormal levels of lactate. They can't tell what's causing the problem.
- Mildly or moderately high blood lactate (hyperlactatemia): Hyperlactatemia means your level of lactate is staying mildly or moderately high, but the acidity of your blood (pH) is still within a normal range. Limitation: If lactate continues to build up, hyperlactatemia can become lactic acidosis. Next step: Your provider will consider your symptoms, medical history, and the results of other tests to diagnose the cause.
- High blood lactate with acidic blood (lactic acidosis): Lactic acidosis means that your lactate level is high enough to make your blood is too acidic, and it is staying high. Limitation: Certain medicines may cause high lactate levels, such as: Metformin, a medicine for type 2 diabetes, Aspirin, Certain medicines to treat HIV called NRTIs. Next step: Lactic acidosis is more serious than hyperlactatemia and needs to be treated right away.
- High lactate in cerebrospinal fluid (CSF): High levels of lactate mean you probably have bacterial meningitis. Limitation: The results of a lactate test can only show whether you have abnormal levels of lactate. Next step: Your provider will consider your symptoms, medical history, and the results of other tests to diagnose the cause.
- Normal or slightly high lactate in cerebrospinal fluid (CSF): Normal or slightly high levels of lactate mean you probably have viral meningitis. Limitation: Low levels of lactate are rare and not considered to be a medical concern. Next step: If you have questions about your results, talk with your provider.
- The test can only show whether lactate levels are abnormal; it cannot diagnose the cause of the abnormality.
- Temporary increases in lactate can occur with exercise or hard physical work, so preparation instructions must be followed to avoid false elevations.
- Clenching your fist during blood collection can temporarily raise lactate levels.
- Certain medicines (e.g., metformin, aspirin, some HIV treatments) may cause high lactate levels, which could affect interpretation.
- Results from a blood sample taken from an artery may be more accurate than from a vein, but the test still cannot identify the underlying condition.
What to do next
Treatment for high levels of lactate depends on the condition that's causing the lactate to build up in your blood. Your provider will consider your symptoms, medical history, and the results of other tests to diagnose the cause.
- What symptoms should I watch for that might indicate lactic acidosis?
- How will my test results affect my treatment plan?
- Do I need to repeat this test to monitor my condition?
- Are there any medicines I am taking that could affect my lactate levels?
- What other tests might I need to help diagnose the cause of my abnormal lactate levels?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.