Lactate Test
Reviewed
Also called: Lactic Acid Test, Lactic Acid: Plasma, L-Lactate
This test measures the level of lactate (lactic acid) in your blood or cerebrospinal fluid. High levels can indicate a harmful buildup that may lead to a serious condition called lactic acidosis. The test helps detect high lactate levels early but cannot diagnose the cause.
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 give you specific instructions. You may be told to avoid exercise for several hours before the test and to fast (not eat or drink) for 8 to 10 hours. Tell your provider about all medicines you take, as some may need to be stopped temporarily. Do not stop any medicine unless your provider tells you to.
A health care professional will take a blood sample from a vein or an artery. For a vein sample, a needle is inserted into your arm. For an artery sample, the provider usually uses an artery inside your wrist (or sometimes arm or groin) and may apply numbing medicine first. If meningitis is suspected, a sample of cerebrospinal fluid may be collected via a spinal tap (lumbar puncture).
There is very little risk to having a blood test. You may have slight pain or bruising at the needle site, but most symptoms go away quickly. After a blood test from an artery, you may have some bleeding, bruising, or soreness. Very rarely, the needle may damage a nerve or the artery. You may be told to avoid lifting heavy objects for 24 hours after an arterial blood test.
Understanding results
Your lactate test results can only show whether your lactate level is abnormal. They cannot tell what is causing the problem. Your provider will interpret your results along with your symptoms, medical history, and other tests. The following are possible result patterns:
- High lactate level in blood (hyperlactatemia): Your lactate level is mildly or moderately high, but your blood acidity (pH) is still normal. This may indicate a condition that is reducing oxygen to your cells or affecting how your body uses oxygen. Limitation: This result alone cannot diagnose the cause. Further testing is needed to identify the underlying condition. Next step: Your provider will consider your symptoms, medical history, and other test results to determine the cause and appropriate treatment.
- Very high lactate level in blood (lactic acidosis): Your lactate level is high enough to make your blood too acidic. This is more serious than hyperlactatemia and requires immediate medical attention. Limitation: This result indicates a serious condition but does not identify the specific cause. Next step: Treatment for high lactate levels depends on the underlying cause. Your provider will diagnose the cause and treat it right away.
- High lactate level in cerebrospinal fluid (CSF): You probably have bacterial meningitis. Limitation: This is a presumptive finding; other tests are needed to confirm the diagnosis. Next step: Your provider will likely order additional tests to confirm bacterial meningitis and start appropriate treatment.
- Normal or slightly high lactate level in cerebrospinal fluid (CSF): You probably have viral meningitis. Limitation: This is a presumptive finding; other tests are needed to confirm the diagnosis. Next step: Your provider will likely order additional tests to confirm viral meningitis and recommend appropriate care.
- 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
If you have questions about your results, talk with your provider. Your provider will consider your symptoms, medical history, and the results of other tests to diagnose the cause of abnormal lactate levels and recommend appropriate treatment.
- 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?