Lactate Dehydrogenase (LDH): What Your Result Means

What is Lactate Dehydrogenase (LDH)?

Lactate dehydrogenase is an enzyme found inside nearly every cell in the body. When cells are injured, destroyed, or stressed, LDH leaks into the blood. Because it is everywhere, a high total LDH is a strong 'something is happening' signal with an almost comically long list of possible causes — which is why doctors pair it with organ-specific tests to locate the damage.

Typical reference interval: Reference ranges vary by lab and assay, commonly roughly 140–280 U/L in adults. Note that red blood cells contain a lot of LDH — hemolyzed samples (red cells broken during the draw or transport) can inflate it falsely.. Laboratories differ — the interval printed on YOUR report always governs.

If your Lactate Dehydrogenase (LDH) is high

Common reasons Lactate Dehydrogenase (LDH) runs above the reference interval:

• Red-cell breakdown (hemolysis) — ruptured red cells release large amounts of LDH — including from a poorly handled blood sample
• Liver damage — hepatitis, alcohol, or drug-induced liver injury raise LDH along with ALT/AST
• Muscle injury or extreme exercise — any muscle damage spills LDH — trauma, falls, heavy exertion, or medication-related muscle breakdown
• Heart attack — LDH rises after cardiac muscle damage, though troponin is the preferred modern marker
• Kidney injury or infarction — organ damage anywhere in the body contributes
• Cancer with cell turnover — many tumors shed LDH, and very high values can flag certain blood or solid-organ cancers
• B12 or folate deficiency — immature red cells are destroyed in the marrow, raising the total

If your Lactate Dehydrogenase (LDH) is low

Common reasons Lactate Dehydrogenase (LDH) runs below the reference interval:

• Low muscle mass or sedentary state — less tissue mass to leak means a lower baseline
• No recent cell turnover — low-normal levels are simply the quiet end of the spectrum

Symptoms worth knowing

LDH itself is silent — it is a laboratory echo of damage, not a sensation. The symptoms are those of whatever is damaging tissue: fatigue and jaundice (liver), muscle aches (muscle), or breathlessness (heart).

What usually happens next

1. Treat a high LDH as a clue, not an answer — pair it with organ-specific markers (ALT/AST for liver, CK for muscle, troponin for heart)
2. Rule out sample hemolysis before acting on a single high value — a redrawn sample often normalizes it
3. Persistent very high LDH with weight loss or unusual fatigue warrants a medical workup

Frequently asked questions about Lactate Dehydrogenase (LDH) results