Zinc Protoporphyrin Test

This test, Zinc Protoporphyrin, is ordered primarily to help detect iron deficiency in children and to detect and monitor chronic exposure to lead in adults.

The zinc protoporphyrin (ZPP) test is a blood test that can identify problems in the formation of heme. Heme is an essential part of hemoglobin, the protein in red blood cells (RBC's) that carries oxygen from the lungs to the body's tissues and cells. The formation of heme occurs in a series of enzymatic steps that conclude with the insertion of an iron atom into the center of a molecule called protoporphyrin. If there is not enough iron available, or if ferrochelatase (the enzyme responsible for the incorporation of iron) is blocked, then protoporphyrin combines with zinc instead of iron to form zinc protoporphyrin. Since it cannot transport oxygen, ZPP serves no useful purpose in the RBC's that contain it.

The term ZPP is sometimes used interchangeably with free erythrocyte protoporphyrin (FEP). In reality, about 90% of protoporphyrin in red blood cells is ZPP, while the remainder is present as FEP (not bound to zinc). The testing method for ZPP measures both substances, and the results may be reported as either ZPP or FEP.


No preparation is necessary. In adults, ZPP is measured directly in a sample of whole blood taken by inserting a needle into a vein in your arm. In children, it is often measured as the ZPP/heme ratio, using a drop of blood from a fingerstick and an instrument called a hematofluorometer. This instrument measures the fluorescence of ZPP and reports the amount of ZPP per number of heme molecules.


Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.