What Is a Lactate Dehydrogenase (LDH) Test?

Written by Michele Jordan
Medically Reviewed by Jennifer Robinson, MD and Melinda Ratini, MS, DO on February 10, 2025
7 min read

The lactate dehydrogenase (LDH) test looks for signs of damage to your body’s tissues.

Cars need gas or electricity to go. Your cells need an enzyme (proteins that help speed up your metabolism) called lactate dehydrogenase (LDH). This enzyme helps with cellular respiration, the process that allows your body to turn glucose (sugar) into energy.

Your cells go through a normal cleansing process, ditching old cells and making new ones. When cells are damaged or destroyed, the LDH enzyme is released into your blood.  

LDH tests measure the level of LDH in a sample of your blood or sometimes other body fluids.

LDH and liver function 

Your liver is an important organ that helps filter toxins from your blood. If it’s not working properly, your doctor will want to know. If you’re showing signs of early liver damage like abdominal pain, fatigue, nausea, or loss of appetite, your doctor may order blood tests. 

LDH is one way to tell if you have some liver damage. An LDH test can show signs of liver diseases like hepatitis or cirrhosis. 

There are four stages of liver disease:

Stage 1: Hepatitis. Hepatitis leads to inflammation in the tissue of your liver. Inflammation anywhere in your body often means some injury (like a sprained ankle) or toxicity. When this happens, your body puts up a defense wall (inflammation) – often a temporary fix. If not fixed, hepatitis can lead to scarring of your liver. “In cases of hepatitis, liver cells are inflamed and damaged, leading to increased LDH levels in the blood. However, the test does not necessarily specify where the damage is coming from,” says Didi Mwengela, MD, a gastroenterologist at UCLA in Los Angeles, CA. “Other tests may be reviewed along with LDH to interpret the results.”

Stage 2: Fibrosis. Over time, scarring of your liver, called fibrosis, can reduce blood flow, important nutrients, and oxygen. When this happens, your liver health may begin to decline. But the liver is an amazing organ and can heal itself if the damage isn’t too severe. 

Stage 3: Cirrhosis. If your liver has permanent scarring and not enough healthy cells, this is called cirrhosis. At this stage, your liver won’t be able to regenerate (make new liver tissue). This stage may show up in blood tests like an LDH test or other tests. But you may not have visible symptoms. 

Stage 4: Liver failure. As liver damage increases, you might see and feel symptoms in your body. Yellowing of your skin, eyeballs (jaundice), pain in your upper right abdomen, a swollen belly, nausea, and tremors are a few signs of liver failure. This is a slow process, but it can lead to death if you don't get a liver transplant. An LDH test during the early signs of liver damage may prevent you from getting to this stage. 

There are four main reasons your doctor might suggest an LDH test:

  • To find out if you have tissue damage.
  • To monitor conditions like anemia, organ disease, or infections that might cause tissue damage.
  • To learn how severe cancer might be.
  • To see if certain cancer treatments (like chemotherapy) are working.

Depending on your condition, you may have LDH tests on a regular basis.

You might have an LDH test of different body fluids to:

  • Find the cause of fluid buildup. It could be due to many things, like injury and inflammation. It could also be brought on by an imbalance in the pressure within your blood vessels and the amount of protein in your blood.
  • Help determine if you have bacterial or viral meningitis.

For LDH tests, you’ll have blood drawn through a needle inserted into a vein in your arm. A health care professional will collect a sample of your blood in a test tube. The process is short and typically takes less then five minutes.

Before the test, let your doctor know about all the medicines, supplements, herbs, vitamins, and anything else you’re taking.

If your doctor believes that another condition may be affecting your LDH levels, they may need you to have another procedure to get a sample of the fluid. These may include procedures such as a thoracentesis for fluid in your chest, a lumbar puncture (or spinal tap) to get cerebrospinal fluid (the fluid that moves between your brain and spinal cord), or a paracentesis (also called an abdominal tap) for fluid in your belly.

For an LDH blood test, there are very little risks involved. Most side effects of this test go away fast. They may include:

  • Bleeding
  • Bruising
  • Infection
  • Soreness at the site where blood was taken

 

Higher LDH levels in your blood may be a sign of tissue damage or disease. Your blood LDH level can also let your doctor know if your disease is getting worse or whether your treatment is working. LDH levels that are in the normal or lower-than-normal range aren’t usually a problem.

Normal range LDH

Usually, normal levels range between 140 units per liter (U/L) to 280 U/L for adults and tend to be higher for children and teens.

The specific normal ranges for LDH levels are:

  • Men or assigned male at birth: 134-225 units per liter (U/L)
  • Women or assigned female at birth: 135-214 U/L

Since some labs have different ranges for LDH levels. Check with your doctor to explain what your levels mean based on your medical history. 

High LDH 

Having a high LDH test result can mean several areas of your body aren’t working properly. It can show you have some type of tissue damage (like liver damage).

Higher LDH numbers could be linked to: 

  • Anemia
  • Kidney disease 
  • Lung disease 
  • Kidney disease 
  • Muscle injury
  • Muscular dystrophy 
  • Bone fracture
  • Heart attack
  • Pancreatitis 
  • Certain infections including meningitis, mononucleosis (mono), and HIV
  • Some types of cancer, including melanoma, lymphoma, testicular cancer, and leukemia

Your doctor will treat a high LDH based on the cause. They will likely order more testing to confirm your diagnosis. Other tests like a CBC (complete blood count) or CMP (complete metabolic panel) may be the next step.

Recent studies allow doctors to pinpoint where damage may be. This is not always accurate, so your doctor may order more tests.   

There are five forms of the LDH enzyme which are called LDH isoenzymes. Each isoenzyme has a slightly different structure and is found in specific tissues in your body:

  • LDH-1 is mainly in your heart and red blood cells.
  • LDH-2 is mainly in your white blood cells. It's also found in your heart and red blood cells but in smaller amounts than LDH-1.
  • LDH-3 is mainly in your lungs. Smaller amounts are found in other tissue.
  • LDH-4 is mainly in your kidneys and pancreas. If you're pregnant, it's also found in the placenta (the organ that brings oxygen and nutrients to your baby).
  • LDH-5 is mainly in your liver and muscles.

But elevated blood LDH doesn’t always signal a problem. It might be the result of strenuous exercise. The level may also be high if your blood sample is handled roughly in the lab or not stored at the proper temperature. Your blood LDH also might be high if your platelet (tiny, disc-shaped pieces of cell that help slow bleeding) count is higher than normal.

Low LDH 

Getting a low score on your LDH bloodwork is rare. It can mean you have high levels of vitamin C in your system. Or it can signal a rare genetic condition called lactate dehydrogenase A deficiency (glycogen storage disease XI) or lactate dehydrogenase B deficiency.

Usually, having low LDH isn't a concern and won't mean you need treatment.

An LDH blood test checks for tissue damage by measuring the LDH enzyme in your blood. High levels can mean liver disease, infections, muscle injury, or certain cancers, but more tests may be needed to find the exact cause. The test is a simple blood test. High LDH isn’t always bad. Your doctor will look at your results and may order more tests to figure out what’s going on.

How do I lower my LDH levels? 

Taking care of your overall health and wellness can ensure your body — especially organs like your liver and kidneys — function well. Your doctor will help you figure out the reason for your high LDH and help you bring it back to a normal level.

Can inflammation cause high LDH? 

A high LDH can cause tissue damage in organs like your kidneys and liver. Hepatitis is inflammation in your liver and may show up as a high LDH. 

What cancers does LDH detect? 

An LDH test can help your doctor find out if you might have certain types of cancers. A diagnosis of metastatic melanoma, multiple myeloma, lymphoma, testicular cancer, or leukemia may be confirmed with the help of an LDH test. 

Why do doctors test for LDH? 

Your doctor may order an LDH blood test to check for tissue damage in your heart, liver, kidney, muscles, brain, blood cells, or lungs. The test can also show a low red blood count (anemia) or certain cancers like leukemia (blood cancer) or lymphoma (lymph cancer).