Lactic Acid Blood Test: What Your Levels Mean

Medically Reviewed by Jabeen Begum, MD on March 14, 2024
5 min read

It’s a test that measures the amount of lactic acid (also called “lactate”) in your blood.

This acid is made in muscle cells and red blood cells. It forms when your body turns food into energy. Your body relies on this energy when its oxygen levels are low. Oxygen levels might drop during an intense workout or when you have an infection or disease. Once you finish your workout or recover from the illness, your lactic acid level tends to go back to normal.

But sometimes, it doesn't.

Lactic acid is a chemical made by the body when it breaks down carbohydrates or glucose (stored energy) to use for fuel. It is produced by your cells when you use more oxygen than normal, such as during a strenuous workout. This happens most often in the muscles and blood cells but can occur anywhere in the body. 

What does lactic acid do in the body?

When your body doesn’t have enough oxygen available to fuel its cells, it breaks down glucose to use as energy instead. This process creates lactic acid in the blood. Normally, the kidneys and liver filter out excess lactic acid and turn it back into glucose, which can be used as energy in the future. Lactic acid also spurs your immune system to repair and protect the body. 

Lactic acid that isn’t removed can become toxic for the body. High levels of lactic acid can decrease the pH of the blood and result in a condition called lactic acidosis. Without treatment, this can cause problems with your heart, organ failure, or even death.

If lactic acidosis is severe enough, it can upset your body’s pH balance, which indicates the level of acid in your blood. The condition can lead to these symptoms:

If lactic acid buildup is suspected, your doctor will order a lactic acid blood test. Signs of high levels of lactic acid include the following:

  • Being very tired
  • Nausea
  • Vomiting
  • Rapid heart rate
  • Fast breathing
  • Yellowing of the skin
  • Muscle cramps
  • Weakness
  • Confusion
  • Not urinating
  • Trouble with walking or coordination

It’s a simple blood test. Your doctor will draw blood from a vein or artery using a needle. In rare cases, they may take a sample of cerebrospinal fluid from your spinal column during a procedure called a spinal tap.

Normally, you don’t have to adjust your routine to prepare for the test.

If your lactic acid level is normal, you don’t have lactic acidosis. Your cells have enough oxygen and your liver and kidneys are processing lactic acid normally. It also tells your doctor that something other than lactic acidosis is causing your symptoms. They’ll likely order other tests to find out what it is.

If your lactic acid level is high, it could be caused by a number of things. Most often, it’s because you have a condition that makes it hard for you to breathe in enough oxygen. These conditions include:

A higher-than-normal lactic acid level in your blood can also be a sign of problems with your metabolism. And your body might need more oxygen than normal because you have one of the following conditions:

Elevated lactic acid levels can also mean you’re not getting enough vitamin B1.

Normal lactate range

During hard physical activity, your lactate range may be higher. But when you're at rest, the normal level for lactic acid in the blood is less than 2 mmol/L (millimoles per liter). Millimoles are a scientific unit used to measure chemicals.

High lactic acid levels

Your lactic acid level is high if it is between 2 and 4 mmol/L. This is called hyperlactemia or lactic acidosis. Lactate levels over 4 mmol/L are considered severe. High lactic acid requires treatment to reduce the lactic acid in your blood and raise your blood’s pH back to a normal level. 

If you are showing signs of lactic acidosis, your doctor will do a lactic acid blood test. Treatment is needed to lower your blood lactic acid level if your results are 2 mmol/L or higher. If not, then something else is causing your symptoms. Either way, your doctor will use the lactic acid blood test to diagnose your illness and come up with a treatment plan.

What is the main cause of lactic acidosis?

Lactic acidosis is caused by either your cells producing too much lactic acid or not being able to filter out this excess – or sometimes both. Often, this happens due to a disease that causes low oxygen levels in the body or disrupts the metabolism of lactic acid. These include diseases of the lungs, circulation, metabolism, blood, immune system, kidneys, or liver. HIV, AIDS, cancer, diabetes, genetic conditions, seizures, alcohol use disorder, vitamin B1 deficiency, certain medications or drugs, or carbon monoxide poisoning can also be to blame. Intense periods of exercise can temporarily cause lactic acidosis.

How do you fix lactic acidosis?

Lactic acidosis is fixed by treating the condition that’s causing it. Healthy lifestyle choices, such as drinking plenty of water, regular exercise, getting enough sleep, and limiting alcohol and drug use, can also help. But any chronic medical issues need to be addressed as well.

How do you get rid of lactic acid in your body?

Early treatment usually includes rest, IV fluids, and oxygen therapy, if necessary, as well as finding the cause. If it’s due to overexertion, stopping exercise and taking it easy may be all that’s needed for your body to clear the lactate buildup. If your lactic acidosis is due to another medical condition or medication, you’ll need to get that issue under control to clear the lactic acid from your body.