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Understanding the Lactate Dehydrogenase (LDH) test: Purpose and risks

Dr. BhavikaJan 17, 2024

Patients often wonder why blood tests are among the first things doctors advise, sometimes even at the time of the first visit. It is because some simple blood tests can be very insightful in understanding your health status.

The Lactate Dehydrogenase (LDH) test is one such way to know if there is any tissue injury. LDH is an enzyme normally found inside cells and tissue. Much like water spills out of a pot when it is cracked, LDH leaks out of cells into the bloodstream when they are damaged. Read ahead to get an overview of the Lactate Dehydrogenase test.




What is a Lactate Dehydrogenase (LDH) test?

The LDH test is a way to measure the levels of Lactate Dehydrogenase (LDH) in the blood and other bodily fluids. LDH is an enzyme that is found in several tissues and organs in the body, like blood cells, heart tissue, muscles, kidney, brain, lungs, etc.

When any of these organs are injured because of inflammation, abnormal growth like a tumour, or infection, LDH levels in the blood are raised. In addition, it is also used to monitor the response of cancer patients to chemotherapy.

LDH as an enzyme plays an important role in energy production in the body. When you eat carbohydrates, your body has to convert glucose into energy. This is a long process and LDH has an important role to play in it. It also works to prevent muscle failure and fatigue in many ways.

What type of sample is needed for a Lactate Dehydrogenase (LDH) test?

The LDH test is most often performed on a blood sample. The process is pretty straightforward. Blood is usually drawn from veins. A trained professional will clean the site, and using a needle, access your vein through a small prick. A small amount of the sample will be collected. This process is practically painless when done by an expert.

You are not required to be fasting prior to giving the sample for an LDH test. Inform your doctor regarding your current medications at the time of prescribing the LDH test, so they can tell if you are required to stop taking a certain medicine prior to the test.

There are also conditions in which LDH levels are tested in other body fluids, such as when fluid gets collected in the abdomen. The process of draining and sampling such fluids is very different and requires a hospital setting.

Are there any risks of performing a Lactate Dehydrogenase (LDH) test?

We know blood tests are scary. Unfortunately, there is no way around them. The LDH test is not linked with any major risks. You may experience some pain or bruising at the blood-drawing site for a few hours. Rarely, a small painful red bump may form at the site called a hematoma. This happens because of the collection of blood under the skin. It is not a cause of worry and usually resolves on its own in a few days.

When is a Lactate Dehydrogenase (LDH) test prescribed?

The LDH test from a blood sample is usually prescribed in one of the following situations.

  1. Suspicion of tissue/organ damage (for example, myocardial infarction, acute liver injury, acute kidney injury, etc.)

  2. Suspicion of hemolysis: A condition in which the red blood cells present in your blood are breaking down.

  3. In cancer patients to observe the progress of chemotherapy. A high LDH level after chemotherapy is an indication of poor response and could mean that the medications have caused some tissue damage.

  4. Suspicion of sepsis: A potentially life-threatening condition that can occur when your body is trying to fight off any serious infection. It can also result in multiorgan failure.

  5. Infections like meningitis.

  6. Inflammatory conditions like pancreatitis.

  7. To monitor the progress of chronic diseases such as HIV/AIDS.

As mentioned before, LDH can also be measured from other bodily fluids. When doctors are suspecting a specific disease and can collect fluid from the related organ, they may suggest one of these:

  1. Pleural effusion: Testing LDH from a pleural fluid sample is helpful in diagnosing the cause of the fluid, thereby enabling targeted treatment.

  2. Cerebrospinal fluid (CSF) - Cerebrospinal fluid is present around the brain and spinal cord. It can be collected and tested when there is a suspicion of meningitis and encephalitis (infections of the brain and spinal cord). The test value can help understand the severity of the disease as well.

In some cases, the LDH test is prescribed along with a panel of other tests such as a liver profile test. This will test all the enzymes related to liver function.

What is the normal level for a Lactate Dehydrogenase (LDH) test?

The normal range for Lactate Dehydrogenase in the blood is between 50 to 150 U/L. A small amount of LDH exists in your bloodstream always, because the cells and tissues in the body are continuously being replaced, resulting in older cells being destroyed and excreted. This releases a small amount of LDH which is normal.

What do abnormal levels mean in a Lactate Dehydrogenase (LDH) test?

A high LDH level is an indicator of cell or tissue damage. It can be an indicator of underlying organ dysfunction (heart, liver, kidney, etc.), infection & sepsis, or any malignant cellular activity. A high LDH level in patients who have undergone chemotherapy for cancer treatment is an indicator of poor response to therapy.

Low LDH levels can be caused by the ingestion of a large amount of Vitamin C. A low LDH level is not pathological.

It is important to understand that an LDH test by itself does not give a specific diagnosis. It just gives a hint that something is wrong. However, research has taken us one step further. We now know that there are 5 different types of LDH called LDH isoenzymes.

The way this helps is because different types of LDH are raised in different conditions. For example, if LDH 5 levels are higher than LDH 4, it could indicate a liver disorder. Talk to your doctor to understand why this test is prescribed for you, and how it is interpreted in relation to you. Following this, you may be recommended further investigations to diagnose your medical condition and treat it.

Frequently Asked Questions (FAQs)

Here’s a list of common questions and answers related to the Lactate Dehydrogenase Test.

What does the LDH test aim to achieve?

The LDH test is one of many routine tests that give doctors a peek into the functioning of your body.

What is the use of the LDH test?

With medical research advancing each day, such simple tests prevent the need for more invasive investigations.

How to interpret theLDH test results?

The LDH test may show higher levels in a wide variety of cases. Hence, it is important to let your doctor explain the significance of the results before getting worried or scared.

Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. Please consult a doctor before making any health-related decisions.


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