LDH too high: what does this blood value mean?

A high LDH value usually doesn't mean something serious is going on. LDH (lactate dehydrogenase) is an enzyme found in almost all your cells, from muscles to red blood cells. So it can rise after a heavy workout, but also from dozens of other, often harmless causes. It's a non-specific value.

I sometimes see people startle at a high LDH, because online you quickly land on scary causes. In practice the context is almost always more important than the number itself.

What is LDH?

LDH plays a role in the energy metabolism of your cells. Because the enzyme is present in so many tissues, some LDH is released whenever cells are broken down or damaged somewhere. So a raised LDH says there's something, but not what.

That's the heart of it: LDH is sensitive but not specific. It points a direction, not a diagnosis.

Why is a high LDH often not alarming?

Precisely because LDH is everywhere, many causes of a mild rise are everyday. A solid workout, a recent infection, or even the way your blood was drawn can affect the value. A single, mildly raised LDH without symptoms is usually no reason to panic.

That doesn't mean you should ignore it. It means you should read it in context, together with your symptoms and other values.

For the bigger picture of sport and blood, read the pillar blood values for athletes.

Can sport raise my LDH?

Yes. With exertion some muscle damage can occur, and then LDH is released alongside creatine kinase. Serum enzymes such as CK and LDH are tracked together after load in sports medicine for this reason (Brancaccio, 2008). The rise is usually temporary.

If you trained hard shortly before the blood test, keep that in mind. A rest period before the measurement gives a fairer picture of your resting value.

What other causes are there?

A raised LDH can come from many sides. The table below gives a few known causes and why a doctor rarely relies on LDH alone.

Why does a doctor read LDH with other values?

Because LDH is so non-specific, it only gains meaning in combination. If your CK is also high, that points towards muscle. If your liver values are raised, the doctor looks that way. So LDH is an addition, not a stand-alone answer.

There's more on that muscle enzyme in CK value too high. You can also check the single value LDH, as well as lactate, to which it is related.

When do you see your GP?

Discuss a raised LDH with your GP if you have symptoms with it, if the value is sharply raised, or if it stays high on repeat testing. The GP can decide whether further tests make sense. A single, mildly raised value without symptoms is often no alarm.

See your result as a starting point for that conversation, not a diagnosis on its own.

What if your LDH stays high?

A single raised LDH says little, but a value that stays high on repeat testing can be a reason to look further. Your GP weighs that together with your symptoms and other results. Sometimes the test is repeated after a few weeks to rule out a temporary cause.

Bear in mind too that the way blood is drawn matters. If red blood cells break down during or after the draw, the LDH can look falsely raised. A fresh draw then sometimes gives a very different picture.

What stays important: don't hang your whole health on this one enzyme. LDH is a tool that gives direction, and it's up to your GP to decide whether and when further testing makes sense.

Getting started

If you want to see LDH in a broader picture, the Extended Health Checkup maps several markers at once. That way a single value doesn't stand alone.

References

1. Brancaccio P, Lippi G, Maffulli N. Biochemical markers of muscular damage. Clin Sports Med. 2008. PMID 18206566.
2. Thuisarts.nl. I am having my blood tested. Dutch College of General Practitioners.
3. RIVM. Physical activity and health. National Institute for Public Health and the Environment.

Disclaimer

Caliberhealth works with BIG-registered doctors who assess your blood results. This article gives general information and is not a substitute for medical advice from a GP or specialist. A blood test is a tool, not a diagnosis in itself. For serious symptoms, contact your GP, or in an emergency call 112.