C16-OH (3-hydroxypalmitoylcarnitine)

This test measures 3-hydroxypalmitoylcarnitine, often abbreviated C16-OH, in your blood. C16-OH is a long-chain acylcarnitine that forms when the body breaks down certain fats for energy inside mitochondria. Measuring it helps assess how well your body is performing long-chain fatty acid oxidation.

The test is typically performed by tandem mass spectrometry on a dried blood spot or a plasma sample. It is commonly included in newborn screening panels and in broader acylcarnitine profiles when doctors are evaluating possible inherited metabolic conditions or unexplained low blood sugar, muscle symptoms, or heart issues.

C16-OH can be higher than expected when there is a problem with long-chain fatty acid oxidation, such as long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency or mitochondrial trifunctional protein deficiency. Finding these conditions early can guide nutrition and medical plans that help prevent metabolic crises, muscle breakdown, or heart and liver complications.

Your clinician may order this test after an abnormal newborn screen, during evaluation of unexplained low blood sugar or muscle pain, or if there are signs that suggest a fatty acid oxidation disorder. Results are most useful when interpreted alongside other acylcarnitines, clinical symptoms, and additional laboratory tests.

A higher than expected C16-OH result does not by itself make a diagnosis. Your clinician will consider your symptoms, other acylcarnitine results, and follow-up tests such as urine organic acids, plasma acylcarnitines, and genetic testing. Sometimes a repeat sample is collected when you are well fed and not acutely ill to confirm the pattern.

Levels can be influenced by diet, fasting, intercurrent illness, and some medications or supplements. If results suggest a fatty acid oxidation disorder, your care team may recommend specific dietary changes, an emergency sick-day plan, and referral to a metabolic specialist. For newborns, results may reflect early feeding status or maternal factors, so repeat testing and clinical follow-up are often part of the evaluation.