Lactate dehydrogenase (LDH)

Lactate dehydrogenase (LDH) is a cytoplasmic zinc-containing enzyme that participates in the final stages of glycolysis, catalyzing the reverse conversion of lactate (lactic acid) to pyruvate. The enzyme is present in almost all human tissues and organs, with the highest concentrations in the heart, kidneys, liver, skeletal muscles, erythrocytes, and lungs.

Normally, LDH is present in small amounts in the bloodstream. When cell membranes are damaged or destroyed (cytolysis), the enzyme is released into the blood in large quantities. The LDH content increases in proportion to the volume of the affected tissue, which makes it a highly sensitive indicator of pathological processes.

Indications for appointment

• Diagnosis and monitoring of tissue damage: Comprehensive examination in case of suspected myocardial infarction, pulmonary or renal infarction.

• Hematological studies: Differential diagnosis of anemias (hemolytic, B12-deficient, folate-deficient), assessment of the degree of erythrocyte hemolysis.

• Oncology: Assessment of the prevalence of the tumor process, monitoring the effectiveness of chemotherapy, detection of relapses (in particular, in lymphomas, seminomas, melanoma).

• Liver and kidney pathologies: Acute and chronic hepatitis, toxic lesions, cirrhosis, acute renal tubular necrosis, pyelonephritis.

• Diseases of the muscular system: Muscle injuries, dermatomyositis, polymyositis, muscular dystrophy.

Interpretation of results

The indicated reference values are approximate. The final diagnosis is established by a doctor based on the clinical picture and a comprehensive examination.

Causes of increased LDH levels:

• Cardiovascular pathologies: Myocardial infarction, acute heart failure, pulmonary embolism, myocarditis.

• Hematological disorders: Hemolytic, megaloblastic and pernicious anemia, acute leukemia.

• Liver disease: Viral, toxic and alcoholic hepatitis, mechanical jaundice, cirrhosis.

• Oncological diseases: Malignant neoplasms of various localization, presence of metastases.

• Other states: Burn disease, skeletal muscle injuries, acute pancreatitis, infectious mononucleosis, renal infarctions, intense physical overload.

Reasons for decreased LDH levels:

• Positive dynamics and effectiveness of the therapy (for oncological or hematological diseases).

• Taking high doses of ascorbic acid (vitamin C).

Preparation for the study

1. Nutrition: Blood is donated strictly on an empty stomach in the morning (after 8–12 hours of fasting). It is allowed to drink clean, non-carbonated water.

2. Restrictions on the eve: 24 hours before blood sampling, you should avoid fatty and fried foods, alcohol, and also refrain from intense physical exercise and visiting the sauna.

3. Smoking: Do not smoke for at least 1–2 hours before the test.

4. Medicines: In consultation with your doctor, temporarily stop taking medications that affect LDH levels (aspirin, statins, NSAIDs, narcotic analgesics).

5. Emotional state: Immediately before blood sampling, you should rest for 10–15 minutes in a quiet environment.

Frequently Asked Questions (FAQ)

1. Can I take an LDH test after eating? or during the day? No, to obtain reliable results, blood must be donated strictly on an empty stomach. Eating can affect the composition of the serum and lead to false distortion of the indicators.

2. Why can LDH levels be elevated after the gym? Intense physical activity causes microtrauma to muscle fibers. Since LDH is found in skeletal muscles, the release of this enzyme into the blood after exercise is a natural physiological process. That is why it is recommended to avoid physical activity the day before the analysis.

3. With what additional tests is LDH usually prescribed? Since LDH is a general (non-specific) marker of cell destruction, your doctor will order additional tests to determine the specific organ affected. Most often, these are ALT, AST, bilirubin (to check the liver), creatine kinase and troponin (to diagnose the heart), or a complete blood count (to detect anemia).

Recommendations after receiving the results

• Avoid self-diagnosis. Deviation of LDH levels from the norm is not an independent diagnosis, but only signals the presence of a pathological process that requires additional examination.

• Doctor's consultation. With the results obtained, you should contact a specialized specialist (general practitioner, cardiologist, hematologist, gastroenterologist, or oncologist) for correct interpretation in combination with your symptoms.

• Additional examinations. If LDH is elevated, the doctor may recommend taking an analysis for LDH isoenzymes (they allow you to accurately determine which organ is damaged) and undergoing instrumental diagnostics (ultrasound, ECG).