Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
This test measures C18:1-OH, also known as 3-hydroxyoctadecenoylcarnitine, a long-chain 3-hydroxy acylcarnitine formed when your body breaks down certain fats for energy. Acylcarnitines act as carriers that help move fatty acids into mitochondria, the energy-producing parts of cells.
It is usually performed on a blood sample using tandem mass spectrometry, often as part of an acylcarnitine profile. The result helps clinicians assess how well long-chain fatty acid oxidation is working, particularly in settings like newborn screening or when there are symptoms that suggest a problem with fat metabolism.
C18:1-OH is a marker that can rise when long-chain fatty acids are not being processed efficiently. Patterns that include this marker can point to conditions such as long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency or mitochondrial trifunctional protein deficiency. Identifying these issues early can guide diet and medical care to support energy needs and reduce the risk of complications.
Your clinician may order this test after an abnormal newborn screen, when there are episodes triggered by fasting or illness, or if there are concerns such as muscle pain, weakness, heart involvement, or liver problems. Results help determine whether more specialized metabolic and genetic testing is needed and whether preventive steps, such as avoiding prolonged fasting, should be put in place.
Your result is interpreted alongside other acylcarnitines, your symptoms, and clinical history. A higher-than-expected value can be seen in inherited fatty acid oxidation disorders, but it can also rise temporarily during illness or if you have recently received certain nutrition or medications. A single result does not confirm a diagnosis, so clinicians look for a consistent pattern and may repeat the test when you are well.
If your result is unexpected, your care team may suggest follow-up tests such as a full acylcarnitine profile, urine organic acids, plasma free and 3-hydroxy fatty acids, and, in some cases, genetic testing. Management typically focuses on preventing energy shortages by ensuring regular intake, adjusting fat sources under specialist guidance, and making a plan for times of illness. Your clinician will discuss what your specific result means for you and whether any immediate steps are needed.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Being fasted or acutely ill can shift the body into a catabolic state, increasing long-chain 3-hydroxy acylcarnitines such as C18:1-OH. Tell your clinician if the sample was taken during fever, vomiting, or poor intake.
Newborns, especially if preterm, can show transient elevations as metabolism adapts after birth. Age-specific interpretation is important, and repeat testing may be recommended.
Parenteral nutrition, lipid emulsions, high-fat medical formulas, or carnitine supplements can alter acylcarnitine patterns. Share details about recent feeds, specialized formulas, or supplements.
Some medicines, such as valproate, high-dose salicylates, certain anesthetics, and antiretrovirals, can influence fatty acid oxidation and acylcarnitine levels. Provide a complete medication list.
Recent blood transfusion or exchange transfusion can dilute or mask abnormal acylcarnitine results. Timing of the test relative to procedures should be noted.
Differences between dried blood spot and plasma, delayed processing, or hemolysis can affect measurements. Proper collection and prompt handling improve reliability.
In pregnancies at risk for a fetus with a fatty acid oxidation disorder, maternal metabolites can shift. Discuss any pregnancy or postpartum status with your clinician.
References