Methemoglobin is a form of hemoglobin (HEEM o glo bin). Hemoglobin is a substance in blood that carries oxygen and distributes it to your tissues and organs. However, methemoglobin is not a type of hemoglobin that is useful in carrying oxygen. Methemoglobin normally exists in small amounts in the blood. However, when methemoglobin levels increase, the blood is less efficient in circulating oxygen. The resulting lack of oxygen throughout the body can cause symptoms such as pale or blue-colored skin. Methemoglobinemia is a condition in which methemoglobin is present in high levels in the blood. Methemoglobinemia usually occurs when a person is exposed to certain drugs or chemicals such as nitrites. It may also be caused by a genetic disorder. Methylene blue injection is used to treat methemoglobinemia. It works by converting methemoglobin to a more efficient type of hemoglobin to better carry oxygen throughout the body. Methylene blue oral is used to treat methemoglobinemia and urinary tract infections. It works as a mild antiseptic to kill bacteria in the urinary tract. You will most likely also be given an antibiotic medication to treat your infection. Methylene blue is also used as a dye or staining agent to make certain body fluids and tissues easier to view during surgery or on an x-ray or other diagnostic exam. Methylene blue may also be used for purposes not listed in this medication guide.