Lactic acid is a vital component for the proper working of the body. It increases in concentration during exercise but does not cause muscle soreness.

Lactic acid is integral to bodily function and is not solely a byproduct of exercise.

Some health conditions can increase lactic acid production or reduce the body’s ability to clear lactate from the blood. This can result in a more severe buildup of lactate, which doctors refer to as lactic acidosis.

In this article, we outline what lactic acid is, its role in the body, and the symptoms of lactic acidosis.

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The body uses lactic acid at a whole-body level. It plays an important role in the correct working of cells, tissues, and organs.

Lactic acid has three main uses in the body:

  • as a major energy source for mitochondria
  • as a precursor for producing glucose
  • as a signaling molecule

Doctors previously thought that muscles produced lactic acid when low on oxygen. Research has shown this to be false. Lactic acid production is fully aerobic, meaning it occurs during normal respiration.

Neither lactic acid nor lactate are responsible for muscles soreness or burning sensations from exercise. In fact, lactic acid is an important fuel source for muscles during exercise, including those in the heart.

Muscle soreness after exercise occurs due to microdamage to muscles. It is not the result of lactic acid buildup in the muscles.

Muscle fatigue and burning during high intensity exercise result from an accumulation of intracellular metabolites such as inorganic phosphate and hydrogen ions that impair the contractile function of the muscle.

Intracellular metabolites are substances within cells that the body makes when it breaks down chemicals in a person’s system.

Lactic acidosis occurs when the body produces too much lactic acid and cannot process or remove it quickly enough. The condition can occur quickly and may lead to severe complications.

Lactic acidosis is often a complication of other health conditions. Some causes of lactic acidosis include:

Certain medications can also cause lactic acidosis. These include metformin, a first-line treatment for diabetes, and nucleoside reverse transcriptase inhibitors, which doctors prescribe to treat HIV.

Liver damage and liver disease impact the body’s ability to remove lactate from the blood. This can result in high blood lactate levels, known as hyperlactatemia. In some cases, hyperlactatemia can progress to lactic acidosis.

Heart failure, shock, and severe infections can reduce blood oxygen levels. This can increase the concentration of lactic acid in the blood, leading to lactic acidosis.

The symptoms doctors associate with lactic acidosis include:

Anyone who thinks they have lactic acidosis or hyperlactatemia should speak with a doctor immediately.

Diagnosis and treatment

A doctor will usually carry out a blood test to check levels of lactate in the blood. In some cases, they may ask the person not to eat, drink, or exercise for several hours before the test.

If the tests detect lactic acidosis, the doctor will work to diagnose and treat its underlying cause. Treatment will allow the body to dispose of the lactic acid in the usual way.

Lactic acid is an integral part of the human body. It assists in cell respiration, glucose production, and molecule signaling. Contrary to belief, lactic acid does not cause muscle soreness. However, the concentration of lactic acid in the blood does increase during exercise.

High levels of lactic acid in the blood can lead to hyperlactatemia and lactic acidosis. Specific health conditions can increase a person’s risk of developing hyperlactatemia and lactic acidosis.

Without treatment, both of these conditions can lead to severe, potentially fatal complications.