Britannica Sources used in this answer

Why does diabetes mellitus cause frequent urination and intense thirst?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

An anatomical illustration of the human pancreas shows its location near the stomach and intestines, a detailed cross-section highlighting ducts and the islet of Langerhans, and an inset of pancreatic tissue histology with labeled alpha, beta, and delta cells. — diabetes mellitus The islets of Langerhans are responsible for the endocrine function of the pancreas. Each islet contains beta, alpha, delta, and pancreatic polypeptide (PP) cells that are responsible for the secretion of pancreatic hormones. Beta cells secrete insulin, a well-characterized hormone that plays an important role in regulating glucose metabolism.

In diabetes mellitus, frequent urination and intense thirst are direct consequences of hyperglycemia, or high blood sugar.12

When blood glucose concentrations rise significantly, the kidneys are unable to reabsorb all the filtered sugar back into the bloodstream. As a result, the excess glucose is excreted in the urine. This high concentration of glucose in the urine creates an osmotic effect, which pulls additional water from the body into the renal tubules. This process leads to polyuria, characterized by the excretion of large volumes of urine and an increased frequency of urination.123

The resulting loss of water from the body's circulation triggers a physiological response of intense thirst, known as polydipsia, as the body attempts to compensate for the fluid deficit. Effectively managing these symptoms typically involves adjusting medication regimens to achieve better control over blood glucose levels.123