Lactate Dehydrogenase (LDH)

What is Lactate Dehydrogenase (LDH)?

Lactate dehydrogenase is an important enzyme involved in converting sugar (glucose) into energy^[1]. It’s found in nearly every tissue in the body but is most prominent in the muscles, liver, kidneys, and red blood cells.

LDH is particularly important for anaerobic metabolism, the conversion of energy when little or no oxygen is available. It catalyses the conversion of lactate to pyruvate and vice versa, an important reaction involved in carbohydrate metabolism^[2].

Why Is LDH Important?

LDH is an important biomarker for tissue damage. Normally, LDH levels in the blood are low because it’s contained inside your cells, However, when cells are damaged or destroyed, they release LDH into the bloodstream, causing an increase in levels. Therefore, a high LDH result can suggest cellular injury, but it’s not useful for identifying which specific cells are damaged^[3].

An LDH test can be used if it is suspected that you may have some cellular or tissue damage. For example, it may be used to diagnose:

• heart attacks – LDH was previously used to diagnose and monitor heart attacks, although different tests are used now, like Troponin T^[4]
• liver disease – high LDH levels can suggest acute liver failure or liver cirrhosis^[5]
• kidney disease – elevated LDH may indicate kidney injury or the progression of kidney disease^[6]
• certain cancers – LDH levels can be monitored to see if cancer treatments, such as chemotherapy, are working, but high levels are observed in some cancers including colorectal, lung, breast, prostate, melanoma, and nasopharyngeal^[7]

How Is LDH Measured?

LDH can be measured as total LDH or as LDH isoenzymes.

Total LDH measures 5 different LDH isoenzymes and reflects tissue damage, but it does not indicate which type of tissue has been injured.

LDH isoenzymes measure 5 different molecular versions of the same enzyme, LDH. Each of the 5 isoenzymes is concentrated in specific tissues, so alongside other tests, can be used to find out what may be causing the cellular damage by identifying the organs or tissues involved.

The 5 isoenzyme locations tend to be as follows:

The LDH reference range can vary depending on the testing laboratory and whether total or LDH isoenzymes are being measured. However, LDH levels are usually reported as units per litre (U/L).

What Do LDH Results Mean?

High LDH levels often suggest some tissue damage, and usually rise as the cells are damaged or destroyed, before peaking and falling back down. Levels of LDH can be increased in the blood with the following conditions:

• stroke
• heart attack
• haemolytic anaemia
• pernicious or megaloblastic anaemias
• intestinal and lung tissue death
• kidney disease
• liver disease
• muscular dystrophy
• inflamed pancreas (pancreatitis)
• some cancers
• some drugs (anaesthetics, aspirin, narcotics, alcohol, and procainamide)

Strenuous or high-intensity exercise can also increase your LDH levels temporarily. LDH levels can indicate your muscle’s response to training, with increasing levels associated with skeletal and cardiac muscles after 3 to 5 hours of activity^[8]. Therefore, it is important to consider if you have taken part in strenuous exercise when you test for LDH because it can cause elevated levels^[9].

Healthy LDH levels do not usually indicate a problem. However, sometimes low levels can be caused by consuming large amounts of vitamin C (ascorbic acid). Research shows that vitamin C can have a protective benefit against exercise-induced muscle damage and can significantly reduce LDH levels^[10].

Rarely, low LDH levels can be caused by a genetic condition, such as LDH A or B deficiency.

Managing Health With LDH Levels

You can promote healthy LDH levels and support your overall health in several ways.

Monitor your vitamin C intake

Consuming lots of vitamin C before your test, may give you a false result because the nutrient can lower LDH levels. However, if your levels are high, you might consider including some vitamin C rich food sources into your diet such as:

• citrus fruits (oranges, lemons, limes)
• peppers
• strawberries
• kiwi
• orange juice

Cut down on strenuous exercise

If your LDH result is high and you regularly participate in strenuous, endurance or high-intensity exercise, it could be causing muscle damage. When muscle cells are damaged, they release LDH into your bloodstream, causing a high result.

Remember to incorporate rest days into your exercise routine to avoid injury, and avoid strenuous exercise before providing a sample for an LDH test. Even moderate exercise, like running, can temporarily raise your LDH levels for 12 to 24 hours^[11].

Limit your alcohol intake

Alcohol raises LDH levels from the liver, stomach, and small intestine in both single and repeated doses^[12]. To avoid elevated LDH levels, it is important to limit your alcohol intake and stick with the guideline of consuming no more than 14 units per week^[13].

Review your current medications

If you are currently taking any medication, whether it’s prescribed, over the counter, or a herbal remedy, it’s important to check if this may be influencing the production of LDH. For example, the following drugs and medications can interfere with your LDH levels:

• aspirin
• anaesthetics
• procainamide
• statins
• recreational drugs (cocaine, narcotics)

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.