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LDH (lactate dehydrogenase)
A general tissue-damage enzyme found in the heart, liver, muscles, and many other tissues.
Other names: Lactate dehydrogenaseSection: Blood chemistry
Updated: August 29, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortA common adult reference range is 125–220 IU/L. High LDH signals tissue damage somewhere in the body; low values are uncommon and rarely a problem.
Reference ranges
Group
Reference range
Adults
125–220 IU/L
Normal value ranges vary slightly among laboratories, and some labs test different samples. Use the reference range printed on your report.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
Lactate dehydrogenase (LDH) is a protein that helps produce energy in the body. It sits inside the cells of many tissues — especially the heart, liver, kidney, muscles, brain, blood cells, and lungs. When cells are damaged, LDH spills into the blood, and the measured level rises. The result is reported in international units per liter (IU/L).
Because LDH is almost everywhere, a high value is a general alarm rather than a pointer to one organ. The meaning of the result depends on why the test was ordered, on your symptoms, and on the other tests done alongside it. If LDH is high, the provider may order an LDH isoenzymes test, which separates the forms of the enzyme and helps locate the damaged tissue.
The test is used in many settings: checking for tissue damage from disease, infection, or injury, and in the work-up of anemia and of blood cancers such as leukemia or lymphoma. In those conditions LDH also serves as a number to follow over time.
Blood is drawn from a vein, and no specific preparation is necessary. One practical detail matters: if many red blood cells break open while the sample is collected or handled, LDH leaks out of them and the result can look falsely high.
When it is high
Heart attackInjured heart muscle releases LDH. A high value after chest symptoms is read together with the heart-specific tests.
Hemolytic anemiaWhen red blood cells are destroyed faster than they are replaced, their LDH pours into the blood.
Leukemia and lymphomaBlood cancers are among the reasons LDH is ordered, and the level helps track these conditions over time.
Liver diseaseHepatitis and other liver diseases release LDH along with the liver enzymes.
Muscle injury and muscular dystrophyDamaged skeletal muscle — from injury or from muscle-wasting disease — raises the level.
Other tissue damageStroke, pancreatitis, infectious mononucleosis, low blood pressure with poor tissue perfusion, and new abnormal tissue growth (usually cancer) can all push LDH up.
When it is low
Usually not a health problemLower-than-normal LDH levels are uncommon and are usually not considered a health problem.
Large amounts of vitamin C or ETaking large amounts of vitamin C or vitamin E may cause low LDH levels.
Lactate dehydrogenase deficiencyA rare genetic disorder called lactate dehydrogenase deficiency can also produce low values.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
Intense exerciseCertain medicines, including aspirinRed blood cells breaking open in the sample
How to prepare
No specific preparation is necessary. Mention intense recent exercise and the medicines you take — including aspirin — because they can shift the result.
When a retest makes sense
If the result is unexpectedly high and the sample may have been damaged during collection, the test is repeated. A confirmed high value is followed by tests that locate the tissue damage, sometimes including LDH isoenzymes.
Who usually reviews this result
A result outside the reference range is usually reviewed by: your GP or primary care doctor; a hematologist if a blood disorder is suspected. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: LDHLD testLactic dehydrogenaseLactic acid dehydrogenase
Units
Measured in: IU/L
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
LDH is present in many tissues — heart, liver, kidney, muscles, brain, blood cells, and lungs — so a high value only says that some tissue is damaged. Symptoms, the reason for the test, and other results supply the location; the LDH isoenzymes test can narrow it down further.
Can the blood sample itself raise LDH?
Yes. If many red blood cells break open when the sample is collected or tested, their LDH enters the serum and the result reads high. A repeat draw settles the question.
Is low LDH dangerous?
Low LDH levels are uncommon and usually are not considered a health problem. Large amounts of vitamin C or E can lower the level, and a rare genetic deficiency exists.
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