Cytochrome b5 reductase
Cytochrome b5 reductase is an enzyme in the blood. It controls the amount of iron in your red blood cells, and helps the cells carry the normal amount of oxygen.
Enzyme
Enzymes are complex proteins that cause a specific chemical change. For example, they can help break down the foods we eat so the body can use them....
Read Article Now Book Mark ArticlePeople who do not have enough of this enzyme may develop a condition called methemoglobinemia.
Methemoglobinemia
Methemoglobinemia (MetHb) is a blood disorder in which an abnormal amount of methemoglobin is produced. Hemoglobin is the protein in red blood cells...

Reviewed By
Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Means Jr. RT. Approach to the anemias. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 144.
Smith-Whitley K, Kwiatkowski JL. Hemoglobinopathies. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 511.