Urine Coproporphyrin III

This test measures the amount of coproporphyrin III in your urine, adjusted to creatinine to account for how concentrated the urine is. Coproporphyrins are intermediate chemicals made during the production of heme, the molecule that carries oxygen in blood. Coproporphyrin III is one of the main isoforms and its level can reflect how well your body is making and clearing porphyrins.

Clinicians often order this test together with other porphyrin and porphobilinogen tests when evaluating symptoms that may suggest a porphyria or a problem with the liver or bile flow. Because many conditions can influence porphyrins, your result is interpreted in the context of other labs, your age, and your symptoms.

Abnormal urinary coproporphyrin III can be a clue to acute hepatic porphyrias, such as hereditary coproporphyria, and can also rise in several non-porphyria conditions like cholestasis, certain liver disorders, medication effects, and heavy metal exposure. It helps your clinician decide if further specialized porphyrin testing is needed, and whether your symptoms might relate to the heme pathway.

This test is often ordered when you have sudden severe abdominal pain, nausea, neurological symptoms, or dark urine, or when routine tests suggest impaired bile flow or liver injury. It can also support follow-up in known porphyria, helping monitor patterns over time alongside more specific tests.

Results are considered together with your symptoms, other porphyrin measurements, and tests like urine porphobilinogen, fecal porphyrins, and sometimes plasma studies. A higher value may suggest increased production or reduced excretion of porphyrins, but it is not specific to one condition. Many common issues, including liver inflammation or certain medicines, can shift coproporphyrin patterns, so a single result rarely gives a final diagnosis.

If your result is higher than expected, your clinician may repeat the test with careful sample handling, review your medication and exposure history, and order additional fractionated porphyrin testing or genetic testing when appropriate. If your result is within expected limits yet your symptoms persist, testing during or soon after symptom flares may be advised. Discuss any concerns with your care team so follow-up is tailored to your situation.