Methylene Blue hydrate is widely used in medical, biological, and chemical fields. In medicine, it serves as an antidote for methemoglobinemia caused by toxins like nitrites or chlorates, where blood cannot carry oxygen effectively. It is also used to treat cyanide poisoning and vasoplegic or septic shock. In diagnostic procedures, such as staining tissues for microscopic examination, it highlights cellular structures. In microbiology, it acts as a vital stain to differentiate living and dead cells. In dentistry, it functions as an oral antiseptic and for treating mouth wounds. Additionally, it is used in surgical settings to mark tissues or as a dye in various procedures. Beyond medicine, it is applied in aquaculture to treat fungal and parasitic infections in fish. In scientific applications, it serves as a redox indicator in oxidation-reduction reactions. Its versatility makes it a valuable tool in clinical, research, and industrial environments.