Lactate Dehydrogenase (LD/LDH) Biomarker Testing
It measures LDH, an enzyme released with cell damage; interpret results with symptoms and other labs, and order through Vitals Vault with Quest access.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
Lactate dehydrogenase (LD, also called LDH) is an enzyme found in many tissues, including your muscles, liver, red blood cells, lungs, and kidneys. When cells are stressed or damaged, LD can leak into the bloodstream, so the test is often used as a broad “signal” that something is irritating or injuring tissue.
Because LD is not specific to one organ, a single abnormal result rarely gives you a diagnosis on its own. The value is in how your LD result fits with your symptoms, your other labs, and whether the number is changing over time.
If you are comparing options or deciding whether to retest, it helps to know what can falsely raise LD (like a difficult blood draw that breaks red blood cells) and what companion tests can narrow down the source.
Do I need a Lactate Dehydrogenase (LD) test?
You might consider an LD test if you have symptoms that could reflect inflammation or tissue injury, but your clinician needs a broad starting point. Examples include unexplained fatigue, shortness of breath, muscle aches, jaundice, dark urine, or persistent fevers, especially when initial testing has not clarified what is going on.
LD is also commonly used as a follow-up marker when there is concern for hemolysis (red blood cell breakdown), certain liver or muscle conditions, or to monitor disease activity in some cancers and blood disorders. In those situations, the trend (rising, falling, or stable) can be more informative than one isolated number.
You may not need LD as a routine screening test if you feel well and your other labs are normal, because it is a nonspecific marker. Testing works best when it supports clinician-directed care and is interpreted alongside targeted labs that point to a specific organ system.
LD is measured in a CLIA-certified laboratory; results should be interpreted in clinical context and are not a standalone diagnosis.
Lab testing
Ready to order an LD test or bundle it with related labs?
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
If you want an LD result you can act on, Vitals Vault helps you order the lab and then make sense of it in context. You can choose LD as a focused test when you are following a known issue, or pair it with related labs when you are trying to localize the source of an abnormal result.
After your blood draw, you can use PocketMD to review what LD typically reflects, what common pre-analytic issues can distort it (like sample hemolysis), and which follow-up tests are usually the next step. This is especially helpful when you are deciding whether to repeat the test, add companion markers, or bring a clearer summary to your next appointment.
If your LD is abnormal, you can reorder to confirm a trend at a consistent lab network and timing, which reduces noise from day-to-day variability and collection differences.
- Order labs directly and choose a convenient draw location
- PocketMD guidance to help you prepare questions for your clinician
- Easy retesting to confirm whether a change is persistent or temporary
Key benefits of Lactate Dehydrogenase (LD) testing
- Gives a broad read on whether cell injury or inflammation may be present somewhere in the body.
- Helps evaluate suspected hemolysis when interpreted with haptoglobin, bilirubin, and a CBC.
- Adds context to liver and muscle symptoms when paired with AST/ALT, alkaline phosphatase, and creatine kinase (CK).
- Supports monitoring over time in certain cancers and blood disorders where LD can track disease activity.
- Can help distinguish a one-time lab artifact from a real problem when you repeat the test under good collection conditions.
- Provides a simple, widely available baseline marker to compare against future results during recovery or treatment.
- Works well as a “bridge” test that guides which more specific labs to order next, rather than guessing.
What is Lactate Dehydrogenase (LD)?
Lactate dehydrogenase is an enzyme your cells use to help convert lactate to pyruvate (and back) as part of energy production. You have LD in many tissues, which is why the test is considered a general marker rather than an organ-specific one.
When cells are damaged, stressed, or break apart, LD can spill into your bloodstream and your measured level can rise. That rise does not tell you exactly where the problem is, but it can confirm that “something is irritating tissue” and help your clinician decide what to check next.
Most modern testing reports a total LD value. Older “LD isoenzyme” testing (separating LD forms from different tissues) is less commonly used today because other tests usually pinpoint the source more reliably.
Why LD can be high without a serious disease
LD can increase from temporary or correctable issues such as strenuous exercise, a recent injury, infection, or a blood sample that was hemolyzed during collection or transport. That is why repeating the test and checking related markers often matters more than reacting to one number.
How LD fits with other labs
LD is most useful when it is interpreted with tests that narrow down the source of cell injury. Common pairings include a complete blood count (CBC) and reticulocyte count for anemia/hemolysis, liver enzymes (AST/ALT) for liver stress, and creatine kinase (CK) for muscle injury.
What do my Lactate Dehydrogenase (LD) results mean?
Low LD levels
A low LD result is usually not clinically concerning. It can occur due to normal biological variation or differences between labs and methods. If you have symptoms, a low LD typically does not explain them, and your clinician will usually focus on other markers that match your situation.
In-range (optimal) LD levels
An in-range LD level suggests there is no strong signal of widespread cell injury at the time of testing. This does not rule out localized problems, early disease, or conditions that do not raise LD. If you are monitoring a known condition, stability over time is often the key takeaway.
High LD levels
A high LD result means more LD is circulating in your blood than expected, which often reflects increased cell turnover or tissue damage somewhere in the body. Common categories include hemolysis (red blood cell breakdown), liver inflammation, muscle injury, lung or kidney stress, and some cancers or severe infections. The next step is usually to confirm the result (especially if the draw was difficult) and interpret it with targeted labs and your symptoms to localize the source.
Factors that influence LD
Sample hemolysis is one of the most important confounders because breaking red blood cells during collection can falsely elevate LD. Recent intense exercise, trauma, surgery, infections, and some medications can also raise LD. Because reference ranges vary by lab and method, it helps to compare your result to the range printed on your report and, when possible, trend results from the same lab over time.
What’s included
- Lactate Dehydrogenase (LD)
Frequently Asked Questions
What is the LDH (LD) blood test used for?
It is used as a general marker of cell injury or increased cell turnover. Clinicians often order it to support evaluation of hemolysis, liver or muscle injury, severe infection/inflammation, or to monitor certain cancers and blood disorders over time.
Do I need to fast for an LD test?
Fasting is usually not required for LD alone. If LD is ordered with other tests that do require fasting (such as a lipid panel), follow the instructions for the full panel.
What can cause a falsely high LDH result?
The most common cause is hemolysis of the blood sample during collection or handling, which releases LD from red blood cells. Recent strenuous exercise, a hard workout, or a recent injury can also raise LD temporarily, so timing and repeat testing can matter.
How high is “too high” for LDH?
There is no single cutoff that applies to every lab because methods and reference ranges differ. Mild elevations are often nonspecific, while larger or rapidly rising elevations usually prompt a more focused workup. Your clinician will interpret the number relative to your lab’s range, your symptoms, and related tests.
If my LDH is high, what other tests are usually checked?
Common follow-ups include a CBC with smear and reticulocyte count, haptoglobin, bilirubin (total and direct), and sometimes a direct antiglobulin test (DAT) if hemolysis is suspected. Liver enzymes (AST/ALT), alkaline phosphatase, and creatine kinase (CK) are also frequently used to look for liver or muscle sources.
How soon should I retest LDH?
That depends on why it was high and whether you had a possible temporary trigger (like intense exercise or a difficult blood draw). For a borderline elevation without concerning symptoms, clinicians often repeat within days to a few weeks to confirm persistence. If LD is being used to monitor a known condition, retest timing is usually tied to your treatment plan.
Is LDH a cancer test?
LD is not a screening test for cancer and it cannot diagnose cancer by itself. In some diagnosed cancers and blood malignancies, LD can be used as a monitoring or prognostic marker because it can reflect tumor burden or rapid cell turnover, but it must be interpreted with imaging, pathology, and other labs.