This test measures the level of lactic acid, also known as lactate, in your blood. Lactic acid is a substance made by muscle tissue and by red blood cells, which carry oxygen from your lungs to other parts of your body. Normally, the level of lactic acid in the blood is low. Lactic acid levels rise when oxygen levels decrease. Low oxygen levels may be caused by:
- Strenuous exercise
- Heart failure
- Severe infection
- Shock, a dangerous condition that limits blood flow to your organs and tissues
If lactic acid levels get too high, it can lead to a life-threatening condition known as lactic acidosis. A lactic acid test can help diagnose lactic acidosis before it causes serious complications.
Other names: lactate test, lactic acid: plasma
What is it used for?
A lactic acid test is most often used to diagnose lactic acidosis. The test may also be used to:
- Help find out if enough oxygen is reaching the body’s tissues
- Help diagnose sepsis, a life-threatening reaction to a bacterial infection
If meningitis is suspected, the test may also be used to help find out if it is caused by bacteria or a virus. Meningitis is a serious infection of the brain and spinal cord. A test for lactate in cerebrospinal fluid is used with a lactic acid blood test to figure out the type of infection.
Why do I need a lactic acid test?
You may need a lactic acid test if you have symptoms of lactic acidosis. These include:
- Nausea and vomiting
- Muscle weakness
- Shortness of breath
- Abdominal pain
You may also need this test if you have symptoms of sepsis or meningitis. Symptoms of sepsis include:
- Rapid heart rate
- Rapid breathing
Symptoms of meningitis include:
- Severe headache
- Stiff neck
- Sensitivity to light
What happens during a lactic acid test?
A health care professional will take a blood sample from a vein or an artery. To take a sample from a vein, the health care professional will insert a small needle into your arm. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes. Make sure you don’t clench your fist during the test, as this can temporarily raise lactic acid levels.
Blood from an artery has more oxygen than blood from a vein, so your health care provider may recommend this type of blood test. The sample is usually taken from an artery inside the wrist. During the procedure, your provider will insert a needle with a syringe into the artery. You may feel a sharp pain as the needle goes into the artery. Once the syringe is filled with blood, your provider will put a bandage over the puncture site. After the procedure, you or a provider will need to apply firm pressure to the site for 5–10 minutes, or even longer if you are taking a blood-thinning medicine.
If meningitis is suspected, your provider may order a test called a spinal tap or lumbar puncture to get a sample of your cerebrospinal fluid.
Will I need to do anything to prepare for the test?
Your health care provider may tell you to not exercise for several hours before the test. Exercise can cause a temporary increase in lactic acid levels.
Are there any risks to the test?
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.
A blood test from an artery is more painful than a blood test from a vein, but this pain usually goes away quickly. You may have some bleeding, bruising, or soreness at the spot where the needle was put in. Though problems are rare, you should avoid lifting heavy objects for 24 hours after the test.
What do the results mean?
A high lactic acid level means you likely have lactic acidosis. There are two types of lactic acidosis: type A and type B. The cause of your lactic acidosis depends on which type you have.
Type A is the most common form of the disorder. Conditions that cause type A lactic acidosis include:
Type B lactic acidosis may be caused by one of the following conditions:
- Liver disease
- Kidney disease
- Strenuous exercise
If you had a spinal tap to check for a meningitis infection, your results may show:
- High levels of lactic acid. This probably means you have bacterial meningitis.
- Normal or slightly high levels of lactic acid. This probably means you have a viral form of the infection.
If you have questions about your results, talk to your health care provider.
Is there anything else I need to know about a lactic test?
Certain medicines cause the body to make too much lactic acid. These include some treatments for HIV and a medicine for type 2 diabetes called metformin. If you are taking any of these medicines, you may be at a higher risk for lactic acidosis. Talk to your health care provider if you are concerned about any medicines you are taking.
Courtesy of MedlinePlus from the National Library of Medicine.