LDH or lactate dehydrogenase: High and low


LDH, or lactate dehydrogenase, is an enzyme found in many different tissues throughout the body. LDH is involved in the conversion of lactate to pyruvate, which is an important step in energy production. The LDH enzyme exists in five different forms, each made up of different combinations of two types of subunits, M and H. The different forms of LDH are found in different tissues throughout the body, and changes in LDH levels can be a sign of various health conditions.

LDH is often measured as part of a routine blood test, and elevated LDH levels can be a sign of tissue damage or disease. For example, LDH levels can be elevated in people with liver disease, heart disease, and certain types of cancer. In some cases, LDH levels can be used to monitor the progress of these conditions and to evaluate the effectiveness of treatment.

LDH is also used in medical research, particularly in studies of cell metabolism and energy production. Scientists can use LDH assays to measure the activity of the enzyme in different tissues and to investigate the effects of different drugs or treatments on LDH activity.

In addition to its role in energy production, LDH has been implicated in other biological processes, such as immune system function and inflammation. For example, some studies have suggested that LDH plays a role in the development of autoimmune diseases and that LDH inhibitors may have potential therapeutic benefits in these conditions.

LDH isoenzymes

LDH (lactate dehydrogenase) is an enzyme that exists in 5 different forms or isoenzymes, each with a slightly different structure and function. These isoenzymes are named LDH-1, LDH-2, LDH-3, LDH-4, and LDH-5, based on their relative mobility during electrophoresis, a laboratory technique used to separate molecules based on their size and charge.

LDH-1 is primarily found in the heart and red blood cells, while LDH-2 is found in the white blood cells, liver, and red blood cells. LDH-3 is found in the lungs and other tissues, LDH-4 is found in the kidneys, placenta, and pancreas, and LDH-5 is found in the liver and skeletal muscles.

By measuring the relative levels of each LDH isoenzyme, it is possible to identify the source of LDH elevation in the blood. For example, elevated LDH-1 levels may suggest heart damage, while elevated LDH-2 levels may indicate hemolytic anemia, a condition where red blood cells are destroyed too quickly.

LDH isoenzyme analysis may also be useful in monitoring the progression of some cancers, as certain types of cancer are associated with specific LDH isoenzyme patterns. For example, lymphoma is often associated with elevated LDH-2 levels.

In summary, LDH exists in five different isoenzyme forms, and analyzing the relative levels of each isoenzyme can help identify the source of LDH elevation and aid in the diagnosis and monitoring of certain conditions, including cancer.

LDH high: Causes

When LDH levels are elevated, it can be a sign of tissue damage or disease. Some common causes of high LDH levels include:

  1. Tissue injury or inflammation: When cells are damaged or inflamed, they release LDH into the bloodstream. This can occur with injuries, infections, or other inflammatory conditions.
  2. Liver disease: LDH levels can be elevated in people with liver disease, such as hepatitis or cirrhosis.
  3. Heart disease: High LDH levels may be a sign of heart disease, such as myocardial infarction (heart attack) or congestive heart failure.
  4. Blood disorders: Certain blood disorders, such as hemolytic anemia or sickle cell disease, can cause high LDH levels.
  5. Cancer: Some types of cancer, such as lymphoma or leukemia, can cause elevated LDH levels.

Elevation of LDH levels alone is not diagnostic of any specific condition, and additional tests and evaluations may be necessary to determine the underlying cause. Additionally, some medications and treatments can affect LDH levels.

LDH low: Causes

Low LDH levels are generally not a cause for concern and are not typically associated with any specific health conditions. However, very low LDH levels can be seen in some rare genetic disorders, such as lactate dehydrogenase deficiency, which is a condition that affects the body’s ability to produce LDH.

In some cases, low LDH levels may be a result of liver disease, where the liver is not producing enough LDH. However, in most cases, liver disease is associated with high rather than low LDH levels.

Laboratory reference ranges for LDH levels can vary depending on the testing method and laboratory used. Therefore, it is always best to discuss any concerns about LDH levels with a doctor who can interpret the results in the context of an individual’s overall health status and medical history.

LDH normal range

The normal range of LDH levels can vary slightly depending on the laboratory used and the testing method. In general, the reference range for LDH in adults is usually around 140 to 280 U/L (units per liter) in most labs. However, some labs may use a slightly different range.

LDH levels can vary based on age, sex, and other factors, and elevated or low levels should always be evaluated in the context of an individual’s overall health status and medical history.

LDH normal range in child

The normal range of LDH (lactate dehydrogenase) levels in children can vary slightly depending on the laboratory used and the testing method.

AgeNormal range (U/L)
1-30 days135-750
31 days – 11 months180-435
1-3 years160-370
4-6 years145-290
7-9 years143-290
10-12 years120-293
13-15 years110-283
16-17 years105-233
≥18 years122-222

Interpretation of LDH

LDH (lactate dehydrogenase) activity can provide insights into the presence and severity of a variety of medical conditions. In certain conditions such as megaloblastic anemia, untreated pernicious anemia, Hodgkin disease, abdominal and lung cancers, severe shock, and hypoxia, there may be marked elevations in LDH levels. Moderate-to-slight increases in LDH levels may be observed in myocardial infarction (MI), pulmonary infarction, pulmonary embolism, leukemia, hemolytic anemia, infectious mononucleosis, progressive muscular dystrophy (especially in the early and middle stages of the disease), liver disease, and kidney disease.

Elevations of LDH in liver disease are generally not as significant as the increases in aspartate aminotransferase and alanine aminotransferase. You can also see the article on transaminitis at peptiko.gr.

In kidney disease, about one-third of patients may exhibit elevated levels of LDH, especially in those with tubular necrosis or pyelonephritis, but these elevations do not strongly correlate with proteinuria or other parameters of kidney disease.

An elevated LDH level may occasionally indicate the presence of a hidden pulmonary embolus. The presence of LDH-2 in myocardium can be used to help diagnose myocardial damage following a severe MI. A diagnostic ratio of LDH-1 divided by LDH-2 greater than 0.9 is referred to as an LDH “flip”. An elevation of LDH-1 not due to myocardial damage may indicate hemolytic disease or other forms of in vivo hemolysis. LDH-5 (least mobile isoenzyme) elevation typically indicates liver damage and is not typically helpful in diagnosing skeletal muscle disease.

In rare cases, macro-LDH can occur, resulting in an elevation of LDH without any clinical reason. Macro-LDH affects the migration of LDH isoenzymes, leading to atypical migration patterns on electrophoretograms. LDH activity is localized near the origin in these cases.

LDH in cancer

Elevated LDH levels are commonly seen in individuals with various types of cancer. LDH levels can be used as a marker of tumor growth and response to treatment. Cancer cells have a high metabolic rate, and as a result, they often produce high levels of LDH. When cancer cells break down glucose for energy, they produce lactate, which is then converted to pyruvate by LDH. This process helps cancer cells to generate energy and grow rapidly.

High LDH levels can indicate the presence of cancer and may also be useful in determining the stage of the cancer, as well as the prognosis and response to treatment. For example, elevated LDH levels have been associated with a poor prognosis in individuals with certain types of cancer, such as lymphoma, melanoma, and lung cancer.

However, LDH levels alone are not diagnostic of cancer, and further evaluation, such as imaging tests and biopsies, may be necessary to confirm a cancer diagnosis.

LDH levels can be elevated in individuals with cancer, and monitoring LDH levels may be useful in assessing the progression of the disease and the response to treatment.

How can I contact gastroenterologist Dr. Zavos for an appointment?

Dr. Chris Zavos is a board-certified gastroenterologist and hepatologist, located in Thessaloniki Greece, and specifically in Kalamaria suburb, about 7 kilometres (4 miles) southeast of downtown Thessaloniki. His private office is at: Fanariou 8 street (near Aigaiou and Adrianoupoleos avenues), Kalamaria (Thessaloniki), Greece.

Thessaloniki International Airport is only 10 km away from his private office in Kalamaria and can be reached by taxi within 13 minutes from the airport.

Dr. Chris Zavos performs endoscopies at Bioclinic private hospital in downtown Thessaloniki (Mitropoleos 86 street).

You can contact Dr. Zavos at phone numbers: (+30)-6976596988 and (+30)-2311283833, or you can email him at czavos@ymail.com. Dr. Zavos responds to Greek and English languages.

Last update: 3 October 2023, 12:33


Gastroenterologist - Hepatologist, Thessaloniki

PhD at Medical School, Aristotle University of Thessaloniki, Greece

PGDip at Universitair Medisch Centrum Utrecht, The Netherlands

Ex President, Hellenic H. pylori & Microbiota Study Group