Lactic Acidosis: Why Too Much Lactic Acid in Your Blood Is Dangerous

Do you remember chemistry class? Maybe something about acids and bases rings a bell. The balance between acids and bases is called the pH level. The normal pH of human blood sits between 7.35 and 7.45. Too much acid decreases the pH, and too much base increases it. If blood pH is abnormal, the body can’t function properly. 

Lactic acidosis occurs when too much lactic acid (also known as “lactate”) builds up in the bloodstream. Left untreated, lactic acidosis can be life-threatening. There are many different causes of lactic acidosis, and treatment depends on the cause. 

What causes lactic acidosis?

Lactic acid is produced by many parts of the body on a daily basis. For example, heavy exercise causes the muscles to produce lactic acid. This is why muscles burn after a sprint. 

Lactic acid itself isn’t dangerous. But you can run into problems when there’s too much of it. Normally, the liver and kidneys get rid of lactic acid after it’s produced, keeping blood pH within the normal range. 

Lactic acidosis occurs when the amount of lactic acid overwhelms the ability of the liver and kidneys to get rid of it. Blood pH drops, and organs struggle to work properly.

People with liver or kidney problems may develop lactic acidosis more easily than others. This is because they have a reduced ability to get rid of lactic acid.

What are the different types of lactic acidosis?

Causes of lactic acidosis fall into two categories: Type A and Type B.

Type A lactic acidosis is caused by hypoperfusion — when tissues don’t get enough blood and oxygen to function properly. For example:

• Infections causing septic shock

• Severe bleeding 

• Heart failure, in which the heart can’t pump blood well enough to reach all tissues

• Cardiac arrest (the heart stops beating)

• Respiratory failure (the lungs stop breathing)

Type B lactic acidosis is caused by a range of different things, including:

• Medications, like metformin

• Seizures

• Certain cancers, like leukemia and lymphoma

• Ingestion of large amounts of alcohol (alcohol use disorder)

• Cocaine

• Ingestion of poisonous substances, like methanol

• HIV infection 

• Short bowel syndrome, which can occur after long parts of the bowels have been surgically removed

• Thiamine deficiency (vitamin B1)

• Rare genetic conditions that cause problems with mitochondria, the parts of cells that help get rid of lactic acid (like MELAS)

What are the symptoms of lactic acidosis?

Symptoms of lactic acidosis aren’t due to lactic acid itself. Rather, they’re due to the fact that there’s too much acid in the blood. Sometimes, people with lactic acidosis will have no symptoms at all. But when symptoms occur, they might include: 

• Confusion

• Feelings of tiredness and weakness

• Fast heartbeat

• Rapid breathing

• Lack of appetite, nausea, or vomiting

In type A lactic acidosis, people also have signs and symptoms of hypoperfusion:

• Low blood pressure

• Cool or clammy extremities

• Decreased urination

• Fast heartbeat

Why is lactic acidosis a problem?

Lactic acidosis makes the blood acidic, lowering the pH outside the normal range. The human body can only tolerate an abnormal blood pH for so long. When the pH is dangerously low for a prolonged amount of time, organs begin to shut down, leading to death.

How do you diagnose lactic acidosis?

Lactic acidosis is always caused by some other problem, and those problems make people quite sick. So, lactic acidosis is typically diagnosed in a hospital, not a doctor’s office.  

Lactic acidosis is easy to diagnose. Simple blood tests can measure the levels of lactic acid in the blood and the blood pH. The tricky part is knowing when to order these tests. In type A lactic acidosis, symptoms of hypoperfusion (like low blood pressure) provide clues. But type B lactic acidosis requires a little more detective work.

How do you treat lactic acidosis?

To treat lactic acidosis, healthcare providers treat the underlying cause. For example, if a poison causes lactic acidosis, they’ll reverse the poisoning. If severe infection with septic shock is the problem, they’ll treat the infection and increase blood pressure with IV (intravenous) fluids. If heart failure is the problem, they’ll treat the heart failure. 

By treating the underlying cause, the production of lactic acid slows down, and the body has time to get rid of it. 

Lactic acidosis is typically treated in a hospital because people with lactic acidosis are quite ill.

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Written by:

Samantha C. Shapiro, MD

Samantha Shapiro, MD, is a board-certified rheumatologist and internist with expertise in autoimmune and inflammatory conditions. She founded the division of rheumatology at Dell Medical School at The University of Texas at Austin.

Edited by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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