Porphyrins are compounds necessary for heme synthesis in haemoglobin metabolism. ALA (delta-aminolevulinic acid) is the basic building block of porphyrins and is involved in the synthesis of coproporphyrin and protoporphyrin. Coproporphyrin is the main porphyrin found in urine, whereas protoporphyrin is the main porphyrin found in erythrocytes. When iron is added to protoporphyrin, the final heme molecule is formed. As the haemoglobin is eventually broken down, these products used for heme synthesis again appear in the blood, urine, and stool as haemoglobin-breakdown products. Clients with one of the congenital or acquired diseases classified as the “porphyrias” secrete and excrete increased amounts of these compounds. The diseases are characterized by neurologic abnormalities, acute abdominal pain, acute cutaneous pain, photosensitivity, or psychiatric disturbances. This test is used most frequently with the measurement of urine porphyrin levels to differentiate the cause and type of porphyria present.