Lactate Dehydrogenase (LDH)

What is Lactate Dehydrogenase (LDH)?

An enzyme present in almost all tissues that helps cells make energy; because it is so widespread, a raised blood LDH is a nonspecific marker of tissue turnover or damage.

Lactate dehydrogenase (LDH) is an enzyme involved in energy production that is present in almost every tissue, with the largest amounts in muscle, liver, kidneys, and red blood cells. When cells anywhere in the body are damaged or turn over rapidly, they release LDH into the blood, so an elevated level is a broad, nonspecific signal rather than a pointer to one organ. This wide distribution is why LDH is used in many different settings, from assessing red-cell breakdown to helping gauge the activity of certain conditions, usually alongside more specific tests. An LDH isoenzyme test can sometimes suggest which tissue is contributing. Because red-cell rupture in the sample itself can raise LDH, careful handling matters, and vigorous exercise or some medicines can also influence the value.

What to know about Lactate Dehydrogenase (LDH)

Understanding Lactate Dehydrogenase (LDH) means knowing what it reflects, what tends to move it, and the signs that suggest it’s worth a closer look — so you can bring the right questions to your next appointment.

How to read a value in context

A 'normal' LDH means the value is within the lab's assay-specific reference interval, but because LDH comes from nearly all tissues it is a low-specificity marker. A normal result does not rule out a problem, and a mildly high result may reflect something as ordinary as recent exercise or a slightly hemolyzed sample. LDH is most useful trended and paired with more specific tests.

Lifestyle factors that influence this marker

• Follow a balanced, mostly whole-food diet that supports general health
• Be aware that very intense or unaccustomed exercise shortly before a blood draw can transiently raise LDH
• Keep up with routine care for any chronic condition your clinician is monitoring with LDH
• Talk to your doctor before making significant changes to your diet, exercise, medications, or supplements

Tests often checked alongside this

• Complete blood count and reticulocytes — relevant when red-cell breakdown (hemolysis) is being considered
• Haptoglobin — supports assessment of hemolysis alongside LDH
• ALT and AST — help judge whether the liver is a contributing source
• LDH isoenzymes — can suggest which tissue is releasing LDH when it is elevated

How this can show up in how you look and feel

• LDH is a blood measurement and does not itself cause symptoms
• A high LDH can be associated with conditions involving tissue damage or increased red-cell breakdown
• Elevated LDH is sometimes seen after intense exercise or with a hemolyzed blood sample rather than any illness
• On its own, a raised LDH does not indicate a specific condition or location

What can affect this marker

• Tissue damage or high cell turnover anywhere in the body
• Red blood cell breakdown, including hemolysis of the sample
• Recent strenuous exercise
• Certain medicines and laboratory assay differences

What to track over time

• Your LDH trend over repeated tests rather than one reading
• Whether more specific tests point to a particular tissue
• Recent exercise or known sample-handling issues
• Related markers such as haptoglobin or a complete blood count

What to ask your doctor

• Given how nonspecific LDH is, what is it being used to monitor in my case?
• Could recent exercise or a hemolyzed sample explain my result?
• Would an LDH isoenzyme test or other specific tests help clarify the source?
• Should LDH be rechecked to confirm the trend?

This glossary entry is for informational purposes only and is not a substitute for professional medical advice. Read our Medical Disclaimer.