Methemoglobin is a form of hemoglobin, the protein in red blood cells responsible for carrying oxygen. In methemoglobin, the iron in hemoglobin is oxidized, which prevents it from binding oxygen effectively. This condition can lead to reduced oxygen delivery to tissues, resulting in symptoms like cyanosis, where the skin appears bluish. Methemoglobinemia is the term used when methemoglobin levels are elevated in the blood. It can occur due to genetic factors, exposure to certain chemicals, or medications. Treatment often involves administering methylene blue, which helps convert methemoglobin back to its normal form, restoring oxygen-carrying capacity.