LDH Test: Purpose, Normal Range, Procedure, Result & More

The LDH test is a blood test that measures the levels of lactate dehydrogenase (LDH) in your blood. LDH is an enzyme that helps to convert lactate to pyruvate, which is then used by your cells for energy. So, a person should have a higher LDH level if they have more lactate in their blood. The LDH test helps to diagnose and monitor conditions that cause high levels of lactate in the blood, such as cancer, heart disease, and liver disease. One can do this test to check for side effects of certain medications.

What is an LDH Test?

The LDH test is a blood test that determines the quantity of lactate dehydrogenase (LDH) in your blood. LDH's function is to change lactate into pyruvate, which provides energy for cells.

What is The Purpose of The LDH Test?

The LDH blood test is used to help diagnose and monitor conditions that cause high levels of lactate in the blood, such as cancer, heart disease, and liver disease. It can also be used to check for side effects of certain medications so that the dosage can be adjusted accordingly. During the LDH test, the healthcare professional will take a blood sample from you and send it to a lab for analysis. The results of your LDH test can help your doctor understand what's going on with your health and make decisions about your treatment.

Why is The LDH Test important?

The LDH blood test is essential because it can help to diagnose various conditions, such as heart disease, liver disease, and certain types of cancer. It can also help to monitor the progress of these conditions. A person should take the LDH test if they have symptoms of high lactate levels, such as fatigue, muscle weakness, and nausea. The LDH test may also be used to monitor for adverse reactions to drugs. After the age of 50, both men and women should take the LDH test every five years as part of a routine health checkup to detect any health conditions early. It's always better to take a test and diagnose a disease than to wait for its symptoms to appear.

LDH Test Procedure (Step-by-Step)

1. You’ll be seated comfortably or asked to lie down, with your arm supported on a rest for stability.
2. An elastic band is placed around your upper arm to make the veins more visible and accessible for the blood test.
3. The healthcare provider examines your arm and selects an appropriate vein, typically in the inner elbow area.
4. The puncture site is cleaned with an antiseptic to prevent infection.
5. A sterile needle attached to a collection tube is inserted into your vein — you may feel a quick, mild pinch.
6. Once adequate blood is collected, the needle is withdrawn, and pressure is applied with gauze to stop bleeding before securing with a small bandage.

What Is The Normal Range for the LDH Test?

LDH Levels by Isoenzyme

• LDH-1: Predominantly found in heart muscle, red blood cells, and kidneys. High levels may indicate heart muscle injury or haemolytic anaemia.

• LDH-2: Found in white blood cells, heart muscle, and red blood cells. Changes in the LDH-1/LDH-2 ratio can help diagnose certain cardiac conditions.

• LDH-3: Mainly found in lungs, spleen, and pancreas. Elevations may suggest pulmonary diseases or certain malignancies.

• LDH-4: Predominant in kidneys, pancreas, and placental tissue, sharing distribution with other soft tissues.

• LDH-5: Found primarily in liver and skeletal muscle. Raised levels often indicate liver disease or muscle injury.

High LDH Levels: Causes & Interpretation

• Blood cell breakdown: Haemolytic anaemia, transfusion reactions, or even rough handling of blood samples during collection can elevate LDH levels.

• Liver conditions: Hepatitis, cirrhosis, and other liver diseases commonly cause raised LDH alongside other liver enzymes.

• Muscle disorders: Intense exercise, muscle trauma, or conditions like muscular dystrophy can increase LDH levels significantly.

• Heart problems: While less commonly used now, LDH can rise after heart attacks, though troponin tests are preferred for diagnosis.

• Lung conditions: Pulmonary embolism, infarction, or severe respiratory diseases may elevate LDH levels, particularly LDH-3.

• Kidney disease: Various renal disorders can moderately increase LDH due to tissue damage.

• Cancer: Leukaemia, lymphoma, and metastatic cancers frequently show elevated LDH because rapidly growing or dying tumour cells release the enzyme.

• Severe illness: Shock, severe infections like sepsis, and multi-organ failure can cause very high LDH levels due to widespread tissue injury.

Low LDH Levels: What They Indicate

Low LDH levels are rare and usually not a cause for concern. Most medical guidance focuses on elevated levels rather than decreased ones. When LDH levels are below normal, it typically doesn't indicate serious health problems. According to MedlinePlus, very low LDH levels can rarely occur in a genetic condition known as lactate dehydrogenase deficiency.

What are The risks Associated With The LDH Test?

There are minimal risks associated with the LDH test. However, as with any blood test, there is a small risk of bruising, bleeding, or infection at the needle's insertion site. In addition, some people may experience dizziness or lightheadedness after having their blood drawn. So, if a person decides to go for an LDH test, they should be sure to tell the doctor or nurse if they have any concerns related to the test. Having a higher-than-normal LDH test means you have some type of tissue damage from an injury, disease, or infection—whether chronic or acute. Conditions that cause high LDH levels include anaemia.

What Should People Do Before Having an LDH Test?

A person should not eat or drink anything for at least six hours before the test and should also avoid taking any medication, such as painkillers, for at least six hours before the test. In addition, the person should fast for at least 12 hours before the test if their doctor has instructed them to do so, and do not ignore these instructions. Fasting for the LDH test is essential because it can help to ensure accurate results.

How is The LDH Test Performed?

The LDH test is a simple blood test. A sample of your blood will be taken from a vein in your arm. The doctor or nurse will insert a needle into your arm and draw the blood into a syringe or vial. After that, the needle is removed, and a cotton ball or Band-Aid is placed over the area where the needle was inserted. The LDH test usually takes less than 30 minutes to complete. It is a little painful, but not much.

What are The Results of The LDH Test?

The LDH test results will be available within a few days. The results will be either normal or abnormal. If the results are abnormal, it is essential to follow up with a doctor to determine the cause. Then a person should visit a doctor to learn about high LDH levels and what can be done to treat them. Most importantly, don't ignore the test results.

Conclusion

In this article, we have discussed the LDH test in detail. We have also asked some essential questions about this test. A person should take the LDH test if they have symptoms of high lactate levels, such as fatigue, muscle weakness, and nausea. The LDH test may also be used to monitor for adverse reactions to drugs. If you have any further questions about this test, then you should visit a doctor so that he can guide you in a better way.

When to See a Doctor After an LDH Test

• Persistent fatigue or weakness following abnormal LDH test results.

• Symptoms like chest pain, shortness of breath, or unusual muscle pain.

• Jaundice (yellowing of skin or eyes) combined with elevated LDH levels.

• Significantly elevated LDH levels should always be investigated further to determine the cause.

• Need for follow-up testing to monitor treatment progress.

FAQs

What is a normal LDH level?

• Normal LDH levels typically range from 0 to 250 U/L for adults.
• Age and gender may slightly influence normal ranges.

What causes high LDH levels?

• Tissue damage from various causes, including liver disease, muscle injury, and cancer
• Blood cell breakdown (haemolysis)
• Heart muscle damage
• Severe infections or inflammatory conditions
• Certain medications and intense physical exercise

Is high LDH serious?

High LDH levels indicate tissue damage but aren't specific to one condition. The significance depends on how elevated the levels are, accompanying symptoms, and other test results requiring medical evaluation.

How is a high LDH level treated?

• Treatment focuses on addressing the underlying cause rather than the LDH level itself.
• May include medications for specific conditions
• Lifestyle modifications depending on the diagnosis
• Regular monitoring through follow-up blood tests

What does LDH indicate in blood tests?

LDH serves as a general marker of tissue damage or cell death, helping doctors identify potential problems requiring further investigation through additional testing.

Is fasting required for the LDH test?

No fasting is required for the LDH test. You can eat normally before this blood test, making it convenient for routine health monitoring.

Does LDH show inflammation?

LDH can rise during inflammation, but it’s not a specific inflammation marker like CRP or ESR — it mainly indicates cellular injury.

Can exercise increase LDH levels?

Yes, intense or prolonged exercise can temporarily raise LDH levels due to normal muscle cell turnover, typically returning to baseline within days.

What cancers can LDH detect?

LDH isn’t specific for any one cancer but is often elevated in blood cancers (like leukaemia or lymphoma) and in many metastatic tumours.

Can LDH be high due to infection?

Yes, serious infections like sepsis can elevate LDH levels due to tissue damage and cellular breakdown caused by the infectious process.