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 can lead to reduced oxygen delivery to tissues, causing symptoms like cyanosis, where the skin appears bluish. Normally, the body maintains low levels of methemoglobin through enzymes that convert it back to regular hemoglobin. However, certain factors, such as exposure to nitrates, aniline dyes, or genetic conditions, can increase methemoglobin levels, leading to a condition known as methemoglobinemia.