Definition

Porphyrins help form many important substances in the body. One of these is hemoglobin. This is the protein in red blood cells that carries oxygen in the blood.

Porphyrins can be measured in the blood or the urine. This article discusses the blood test.

Alternative Names

Protoporphyrin levels; Porphyrins - total; Coproporphyrin levels; PROTO test

How the Test is Performed

A blood sample is needed.

The sample is then placed in ice and taken immediately to the laboratory. Three porphyrins can normally be measured in small amounts in human blood. They are:

• Coproporphyrin
• Protoporphyrin (PROTO)
• Uroporphyrin

Protoporphyrin is normally found in the highest amount. More tests are needed to show the levels of specific porphyrins.

How to Prepare for the Test

You should not eat for 12 to 14 hours before this test. You may drink water right before the test. Your test results may be affected if you do not follow these instructions.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

This test is used to diagnose porphyrias. This is a group of rare disorders often passed down through family members.

It may also be used along with other tests to diagnose lead poisoning and certain nervous system and skin disorders.

Normal Results

This test specifically measures total porphyrin levels. But, reference values (a range of values seen in a group of healthy people) for the individual components are also included:

• Total porphyrin levels: 0 to 1.0 mcg/dL (0 to 15 nmol/L)
• Coproporphyrin level: <2 mcg/dL (<30 nmol/L)
• Protoporphyrin level: 16 to 60 mcg/dL (0.28 to 1.07 µmol/L)
• Uroporphyrin level: <2 mcg/dL (<2.4 nmol/L)

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Increased levels of coproporphyrins may be a sign of:

• Congenital erythropoietic porphyria
• Hepatic coproporphyria
• Sideroblastic anemia
• Variegate porphyria

An increased protoporphyrin level may be a sign of:

• Anemia of chronic disease
• Congenital erythropoietic protoporphyria
• Increased erythropoiesis
• Infection
• Iron deficiency anemia
• Lead poisoning
• Sideroblastic anemia
• Thalassemia
• Variegate porphyria

An increased uroporphyrin level may be a sign of:

• Congenital erythropoietic porphyria
• Porphyria cutanea tarda

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

American porphyria foundation website. Tests for Porphyria Diagnosis. porphyriafoundation.org/for-patients/about-porphyria/testing-for-porphyria/tests-for-porphyria-diagnosis/. Accessed March 27, 2023.

Fuller SJ, Wiley JS. Heme biosynthesis and its disorders: porphyrias and sideroblastic anemias. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 39.