Polydipsia is extreme thirst that can't be quenched. One group of people that suffer from this are undiagnosed diabetics. The renal system can't conserve glucose properly because blood glucose concentrations are too high. The kidneys "spill" glucose into the urine (glycosuria). When this happens water follows glucose into the urine by osmosis (passive process), this results in a net water loss from the body (polyuria). Because of the water loss from polyuria, the person stays thirsty (polydipsia).
The good news is that if we regulate the blood sugar better, all these symptoms will disapear because you will no longer be dumping glucose into the urine.
Polydipsia is when a person is incredibly thirsty and is drinking lots of fluids. They have very high levels of sugar (diabetes) in their bloodstream and the kidneys are working overtime in order to get rid of the sugar. They produce a lot of urine so the body needs fluids in order to replace the lost fluids.
Polydipsia usually occurs in people who have diabetes. It can also be a sign of some kind of fluid imbalance in the body or decrease in blood volume.
Polydipsia is not a disease but it is actually a symptom which means excessive thirst.