Ldh
Lactate dehydrogenase, an enzyme found in almost every tissue. A raised level is a non-specific sign of cell turnover or damage.
Typical reference range
| Range | Unit |
|---|---|
| 120–250 | U/l |
What Ldh measures
LDH (lactate dehydrogenase) is an enzyme found in almost every tissue in the body, from red blood cells and muscle to liver, heart, lung and kidney. Because it sits inside cells, very little normally circulates in the blood; levels rise when cells are damaged and spill their contents. That makes LDH a highly nonspecific marker. A raised result tells you that some tissue turnover or damage is happening somewhere, but it does not point to where or why. For that reason, LDH is rarely interpreted on its own. A clinician reads it alongside more specific tests, your symptoms and the wider clinical picture to work out what a change actually means for you.
What a high Ldh can mean
A high LDH can come from many different places, which is exactly why it is not a diagnosis on its own. Common sources include the breakdown of red blood cells (hemolysis, which can even be caused by a difficult or slow blood draw rather than a real problem), along with injury to the liver, heart, muscle, lung or kidney. Certain infections and some cancers can also raise it. Because so many unrelated conditions push LDH up, a high value is best understood as a prompt to look further rather than an answer. A clinician typically follows it with more targeted tests that can pinpoint the tissue involved. They will also weigh the size of the change, whether it is rising or falling over time, and how you feel before drawing any conclusions.
What a low Ldh can mean
A low LDH is uncommon and, in most cases, is not considered clinically significant. Because LDH is released when cells are damaged, having very little in the blood is generally reassuring rather than concerning. Occasionally a low level relates to certain genetic or metabolic factors that affect how much of the enzyme the body makes, but this is unusual and rarely needs action on its own. In practice, almost all of the clinical interest in this test lies in high values, not low ones. If your result comes back below the reference range, a clinician will interpret it in the context of your other results, your history and your symptoms, and will usually reassure you unless something else in the picture warrants a closer look.
Track your Ldh over time in Quanome — it reads your lab reports (PDF or photo) on your device, charts each marker against its range, and an AI coach explains what your trends mean alongside your Apple Health and DNA.