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Lactate Dehydrogenase (LDH) Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Lactate Dehydrogenase (LDH) Test

The LDH test is a general screening tool used to detect tissue damage throughout the body by measuring the levels of the LDH enzyme in your blood or other body fluids.

Overview

Lactate dehydrogenase (LDH) is an enzyme that facilitates energy production in cells. It is found in nearly all body tissues, with the highest concentrations in the muscles, liver, kidneys, and red blood cells. When these tissues are injured or diseased, they release LDH into the bloodstream or surrounding body fluids. Because LDH is found in so many places, this test is used as a general indicator of tissue damage rather than a specific diagnostic tool for a single condition.

What is it used for?

LDH testing is used to monitor or help diagnose a wide range of acute and chronic conditions, including:

  • Blood disorders, such as anemia
  • Liver, lung, kidney, or pancreatic disease
  • Heart conditions, including heart attack
  • Brain and spinal cord infections (e.g., meningitis or encephalitis)
  • Muscular dystrophy and HIV
  • Various cancers, such as lymphoma, leukemia, and testicular cancer

Test Procedure

The test typically involves a blood draw from a vein in your arm. In some cases, your provider may need to test other body fluids, which may require procedures such as:

  • Lumbar puncture (spinal tap): To collect cerebrospinal fluid.
  • Thoracentesis: To remove fluid from the chest.
  • Paracentesis (abdominal tap): To remove fluid from the abdomen.

No special preparation is required for a standard blood LDH test.

Understanding Results

Elevated LDH levels generally indicate tissue damage from disease, infection, or injury. However, high levels can also result from intense exercise, certain medications (like aspirin), or the accidental breakdown of red blood cells during the testing process. Low levels are rare and usually not a health concern, though they can be caused by high doses of vitamin C or E, or a rare genetic condition called lactate dehydrogenase deficiency.

If your results are high, your provider may order an LDH isoenzyme test to determine exactly which tissue is damaged and the severity of that damage.

Frequently Asked Questions

If the LDH is markedly elevated (often >2‑3 times the upper limit of normal) and you have symptoms such as chest pain, shortness of breath, sudden weakness, jaundice, dark urine, or unexplained fever, seek medical attention promptly. These signs may indicate heart attack, severe hemolysis, liver injury, or other acute conditions that need urgent evaluation.
Exercise can raise LDH for up to 24‑48 hours. If possible, schedule the blood draw on a rest day or at least 24 hours after the most strenuous activity to avoid a falsely high result.
Mildly elevated LDH often reflects a temporary, non‑serious cause such as recent vigorous exercise, a minor infection, or a medication effect. Your doctor will review the exact value, compare it to previous labs, and consider any symptoms before ordering repeat testing or additional studies. If you’re asymptomatic, most clinicians simply monitor and repeat the test in a few weeks.
spirin and some other drugs can raise LDH levels, so it’s best to tell your provider every medication you use, including over‑the‑counter drugs. In most cases you don’t need to stop the medication, but your doctor may ask you to hold it for 24‑48 hours if a very accurate baseline is required.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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