The Purpose of Lactic Acid Testing

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What is Lactic Acid?

Lactic acids levels increase when there is decreased oxygen. An increase in lactic acid may be a result of anaerobic exercise such as sprinting or heavy weight lifting or a disease. In normal metabolism and energy requirements, the muscles break down carbohydrates for energy. In the presence of oxygen the carbohydrate metabolism produces water and carbon dioxide. In the absence of oxygen, carbohydrate metabolism results in lactic acid production. Rapid breathing occurs in an effort to increase the oxygen and eliminate the carbon dioxide that is building up.

Under conditions of anaerobic activity such as heavy exercise, the body will adjust and re-establish equilibrium once the exercise is discontinued, clearing the system of excess lactic acid. There may be muscle stiffness or discomfort but this resolves as the body metabolizes the lactic acid. One of the liver’s functions is to metabolize lactic acid, therefore, the health of the liver is a factor in removing lactic acid from the body. The accumulation of lactic acid can be critical, so a lactic acid test may be done for the purpose of identifying acidic conditions in the body.

Symptoms of Elevated Lactic Acid

Blood levels of lactic acid can increase to dangerous levels under certain conditions. This could be due to difficulty in metabolizing the lactic acid or a compromised respiratory system. Symptoms of increased lactic acid include rapid, shallow breathing, cold and clammy skin, pallor, nausea, vomiting and even coma. The breath may smell sweet and fruity. An individual with extremely high lactic acid may be slow to respond having difficulty speaking cohently.

How the Test is Done

Blood needs to be drawn from a vein, for the purpose of lactic acid test. It is then transported to the lab for analysis. The sample is centrifuged and the testing is done on plasma. The test procedure involves the oxidation of lactate to pyruvate using LDH (lactic dehydrogenase) as a catalyst for the reaction. Normal results for lactic acid are 0.4 - 2.0 mmol/liter with results over than 4.0 mmol/liter considered to be critical.

Diseases With High Lactic Acid

If lactic acid is increased this can be an indication of heart failure which results in diminished capacity to move the blood through the circulatory system. The lactic acid along with carbon dioxide builds up in the bloodstream as it cannot be cleared through the lungs. Liver disease can result in an increased lactic acid as well. The liver is involved in breakdown of lactic acid. Liver disease means that the liver is functioning below normal and cannot respond as needed. The purpose of lactic acid test is to aid physicians to know the severity of the condition.

Other Testing Done With Lactic Acid

Lactic acid testing is primarily done to diagnose lactic acidosis, an acidic condition of the body that can compromise many systems and organs. Other blood tests that would likely be ordered would be a Comprehensive Metabolic Panel (CMP) which includes electrolytes, glucose, as well as several tests to determine kidney and liver functioning. The CMP is a good screening test to evaluate the overall condition of the body. Generally, lactic acid testing would be secondary to screening tests and evaluation of symptoms.


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