All pramehas change into diabetes in the absence of proper treatment. In diabetes the patient passes urine which is as sweet as honey and his body also becomes sweet. That is why it and other Pramehas endowed with these symptoms are called Madhumeha.
In Ayurveda, the main reason of diabetes is believed to be Vayu. When Vata gets aggravated and Oja flows out through urine, the condition is called diabetes. Usually diabetes occurs during the old age when all the Dhatus go on weakening day by day.