Methemagenic refers to the ability of certain substances to induce the formation of methemoglobin in the blood, a condition known as methemoglobinemia. Methemoglobin is a form of hemoglobin that cannot effectively bind oxygen, leading to reduced oxygen delivery to tissues. This can cause symptoms like cyanosis and, in severe cases, can be life-threatening. Common methemagenic agents include certain drugs, chemicals, and food additives.