Platform
Company
Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
U24 Coproporphyrin III is a 24 hour urine test that measures the total amount of coproporphyrin III your body excretes in a full day. Coproporphyrins are natural byproducts made during heme production, the pathway that creates heme for hemoglobin and many enzymes. When this pathway is disrupted, or when the liver and bile system do not process these compounds normally, more coproporphyrins can appear in urine.
This test is part of the broader evaluation of porphyrin metabolism. It is often performed together with other porphyrin tests to help distinguish inherited porphyrias from liver or biliary conditions. The sample is collected over 24 hours in a light-protected container so the laboratory can measure the total daily amount.
Clinicians order this test when symptoms suggest a porphyria, when there is unexplained photosensitive skin fragility, when abdominal pain occurs with neurologic features, or when liver tests are abnormal. Patterns of coproporphyrin excretion can point toward hereditary coproporphyria or other acute hepatic porphyrias, and can also reflect cholestasis, medication effects, alcohol use, or heavy metal exposure. The result helps decide if additional testing such as porphyrin fractionation, fecal porphyrins, plasma fluorescence scanning, or testing for porphobilinogen and aminolevulinic acid is needed.
Beyond diagnosing porphyrias, the test can provide clues in chronic liver disease and in some inherited disorders of bilirubin transport. It can also be used to monitor changes over time or in response to treatment, especially when combined with related porphyrin studies.
Your report shows the amount of coproporphyrin III passed in a complete 24 hour collection. Higher than expected values can occur during an acute porphyria episode, with bile duct blockage or reduced bile flow, or when the liver is stressed by infection, alcohol, or certain medicines. A result within the expected range does not rule out porphyria, because timing, specimen handling, and which porphyrin fractions are affected can influence findings.
If results are surprising or do not match your symptoms, your clinician may confirm that the collection was complete, repeat the test, and order related studies such as total and fractionated urine or fecal porphyrins, plasma fluorescence testing, or ALA and PBG measurements. Next steps depend on your overall health, medications, and family history, so share details about drugs, supplements, alcohol use, occupational exposures, and prior liver issues to help with interpretation.
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.
Missing some urine or starting or stopping the collection at the wrong time can falsely lower or raise the measured amount. Follow the collection instructions exactly and record start and end times.
Porphyrins are light sensitive and can degrade if the container is not protected from light or kept appropriately cooled. Use the provided container, keep it covered, and store as instructed.
Alcohol, barbiturates, rifampin, estrogen-containing therapies, and some anticonvulsants can alter porphyrin metabolism or liver transport. Tell your clinician about all prescriptions, over the counter drugs, and supplements.
Cholestasis, hepatitis, fatty liver, and inherited bilirubin transport disorders can raise urinary coproporphyrins. Interpreting the result alongside liver tests and symptoms improves accuracy.
Exposure to lead or other metals can affect heme synthesis and increase porphyrin excretion. Let your clinician know about workplace hazards, hobbies, or environmental risks.
Pregnancy, infancy, and serious illness can change porphyrin handling and results. Your care team will interpret the test in the context of age, pregnancy status, and overall health.
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