February 26, 2024

What Is a Lactate Dehydrogenase (LDH) Test and Why is it important?

A lactate dehydrogenase test (or LDH test) test is a blood test that checks the levels of an enzyme in your blood. The levels can be used to help diagnose and assess certain diseases and health conditions.

Just about every cell in the body has mitochondria, little powerhouses that use oxygen to create energy. Inside the mitochondria, there’s a molecule called pyruvate made by breaking down sugars in a process called glycolysis.

Pyruvate is a very strong acid and tends to disrupt the chemistry of the mitochondria, where it’s normally localized. So pyruvate is converted into another substance called lactate by another enzyme, lactate dehydrogenase (LDH). And Lactate tends to stay in the mitochondria where it’s needed for energy.

The LDH test checks for two separate types of LDH: 

  • LDH1 and 
  • LDH2. 

And some health conditions are associated with changes in their levels.

To better understand how the LDH test works and what it can tell doctors, here’s a look at the causes, symptoms, and treatments of high or low LDH.

What Is a Lactate Dehydrogenase Test (LDH test)?

A lactate dehydrogenase test (LDH test) is a blood test that checks for the level of an enzyme in the blood called lactate dehydrogenase (LDH).

Levels of lactate dehydrogenase (LDH) can be used to assess several diseases and health conditions, but there are a few exceptions. Here’s the full list:

  • Ischemic Heart Disease 

Also known as “coronary heart disease,” it’s caused by reduced blood flow through the heart or a decrease in heart function. In some cases, it can happen as a result of heart valve problems.

Lactate dehydrogenase (LDH) is found in red blood cells where it plays a role in the breakdown of muscle tissue during exercise. When you exercise at high intensity or do a lot of weight lifting, lactate dehydrogenase (LDH) levels may increase, but this is normal.

A heart attack happens when there’s an obstruction to blood flow through the heart. While it’s not known exactly why heart attacks are more common in some groups, one theory is that it may be related to a build-up of lactate dehydrogenase (LDH).

If you have the test routinely at blood screening, LDH levels can be used as an early indicator of heart disease. Treatments include medications such as beta-blockers and ACE inhibitors.

  • High LDH Levels

LDH levels above 10 are considered high. But the average is closer to 5. Therefore, if your LDH level is above 8, you may want to seek further medical advice.

The LDH test can also be used for: 

  • Dietary Disorders 

People who have diets that don’t include many fruits and vegetables have a higher risk of developing kidney disease, which can lead to elevated lactate dehydrogenase (LDH) levels.

  • Diagnosing Diseases of the Liver 

Lactate dehydrogenase (LDH) levels can be used to assess liver function and diagnose several such as:


  • Testing Drugs for Side Effects 

When drugs are given to people, some may have adverse reactions. For example, the LDH test can measure how well a medication is metabolized by the liver. Some drugs used to treat high cholesterol and triglycerides are metabolized by the liver, but may not work as effectively if they’re administered too often. The LDH test can test the ability of a drug to be metabolized.

  • Checking Out Cancer 

Lactate dehydrogenase (LDH) levels help detect cancer because some cancers have altered the metabolism of the body.

What Are the Causes of High and Low Lactate Dehydrogenase (LDH)?

There can be several causes for high or low lactate dehydrogenase (LDH) levels. When levels are moderately elevated, it may mean the body has an abnormal metabolism of lactate. There are several causes for abnormally low LDH levels. These causes include: 

  • Medications:

Certain medications such as the antibiotics rifampin and ritonavir, and the antidepressant Seroquel can cause high levels of lactate dehydrogenase (LDH). As previously mentioned, it’s also possible that stress can lead to an elevated LDH level.

  • Malnutrition or malnutrition

An immune system that is not at its full capacity can be an issue especially if you are malnourished from multiple causes such as lack of food, water, or medications.

  • Fitness

If you are regularly exercising, then your immune system will be functioning at a high level. This can be an issue if you are doing the exercise at a level that is too intense especially if you do not know your limits.


Recognizing the symptoms of high or low LDH levels depends on the cause. An elevated LDH level doesn’t necessarily mean you have a disease. For example, if your lactate dehydrogenase (LDH) is raised because of an infection, it doesn’t necessarily mean you have an infection. In some cases, it may be caused by stress or eating too much protein. However, elevated levels can be a red flag that an underlying problem exists.

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