Lactic acid test: definition, procedure, test results

Definition

What is lactic acid?

Lactic acid test is a blood test that measures the levels of lactic acid in the body. Most of it is made by muscle tissue and red blood cells. If the oxygen level in the blood is normal, carbohydrates break down into water and carbon dioxide. When oxygen levels are low, carbohydrates are broken down into energy and lactic acid. Lactic acid levels get higher when excessive exercise or other conditions — such as heart failure, severe infection (sepsis), or shock — reduce blood flow and oxygen throughout the body. Lactic acid levels also get higher if the liver is badly damaged, because the liver normally breaks down lactic acid. Very high levels of lactic acid cause a serious, sometimes life-threatening condition called lactic acidosis. Lactic acidosis can also occur in people who take metformin (Glucophage) to control diabetes if they also have heart or kidney failure or severe infections.

The lactic acid test is generally done on a blood sample taken from an artery in the arm but may also be done on a blood sample from an artery (arterial blood gas).

When do I need to have a lactic acid test?

You will need to have a lactic acid test if your doctor needs:

• check if you have lactic acidosis. Symptoms of lactic acidosis include rapid breathing, excessive sweating, cold and wet skin, sweet smelling breath, stomach pain, nausea or vomiting, confusion, and coma.
• see if the right amount of oxygen is reaching the body tissues
• find the cause of high levels of acid (low pH) in the blood

Precautions & warnings

What should I know before taking lactic acid?

The results of the lactic acid test may be more accurate if blood is drawn from an artery (arterial blood gas) rather than from an artery. Clenched fists or bandaged hands for a long time while the blood is drawn can give the result of an incorrectly elevated lactic acid level.

During aerobic exercise, the heart and lungs provide an adequate amount of oxygen to the body for energy. Anaerobic exercise uses more oxygen than the lungs and heart can provide to the body so that it supplies less energy, leading to increased levels of lactic acid in the blood. Usually anaerobic exercise forces a person to slow down or stop exercising because the buildup of lactic acid causes moderate or severe muscle pain and muscle stiffness. However, some highly trained athletes learn to tolerate short periods of high lactic acid levels. During aerobic exercise, the air you breathe contains enough oxygen to use blood sugar normally and completely for the body's energy needs, and lactic acid levels do not increase.

Lactic acid can be measured in fluids other than blood, such as spinal fluid. Lactic acid levels in body fluids often increase if an infection is present. The amount of lactic acid in the spinal fluid may be measured to determine whether a brain infection is caused by bacteria or a virus.

Process

What should I do before taking lactic acid?

To prepare for the lactic acid test:

• Do not eat or drink anything other than water for 8-10 hours before the test
• do not exercise for several hours before the test. Exercise can cause a temporary increase in lactic acid levels

How is lactic acid processed?

The doctor will clean a small area on the arm or elbow with an antiseptic cloth or alcohol pad. In some cases, the doctor will tie an elastic band around your upper arm to increase blood flow. This makes collecting blood from the arteries much easier. Your arm will then be pierced with a needle that the doctor inserts into the vein. The tube that will collect blood is attached to the other end of the needle.

Once the blood is drawn, the doctor will take a needle and then use a cotton cloth and bandage to stop the bleeding from the needle pricked skin.

What should I do after the lactic acid test?

You can return to your normal activities when you finish the test. The doctor will discuss with you about the condition and provide suitable treatment. Sometimes, the doctor may order further tests. Follow the doctor's instructions carefully.

Explanation of the Test Results

What do my test results mean?

The test results will be ready in 1 day.

Normal score

The normal scores listed on this list (called a 'reference range') are only a guide. This range varies from laboratory to laboratory, and your laboratory may have different normal scores. Your laboratory report will usually contain what ranges they are using. Your doctor will also check your test results based on your health condition and other factors. This means that if your test results fall into the abnormal range in this guide, it could be in your laboratory or for your condition the score falls into the normal range.

Venous blood: 0.5-2.2 milliequivalent per liter (mEq / l) or 0.5-2.2 millimol per liter (mmol / l)

Arterial blood: 0.5-1.6 mEq / l or 0.5-1.6 mmol / l

High score

An abnormal result means that the body's tissues are not getting enough oxygen.

A high lactic acid value means lactic acidosis, which can be caused by:

• severe dehydration
• blood problems such as severe anemia or leukemia
• liver disease or damage that prevents the liver from breaking down lactic acid in the blood
• conditions such as severe bleeding, shock, severe infection, heart failure, blockage of blood flow to the intestines, carbon monoxide poisoning, or pulmonary embolism that prevents adequate oxygen from reaching the body's cells
• excessive or too hot exercise
• Poisoning with alcohol (ethanol), wood alcohol (methanol), or antifreeze (ethylene glycol)
• some drugs, for example isoniazid for tuberculosis or metformin (Glucophage) for diabetes. Lactic acidosis is a problem for people who take metformin to control diabetes, especially those with poor kidney function