A blood glucose that is over 15 mmol/l can quickly weaken the insulin-producing beta cells.

When it drops to more normal levels, 5-10 mmol/l, the beta cells often become healthier and stronger again in just a few days and the glucose stabilizes because the own production of insulin is then sufficient again.

It is this weakening of the insulin production of the beta cells that can cause a temporary infection or other stress to trigger diabetes from having previously been prediabetes.

When blood glucose is over 15 mmol/l, you usually urinate a lot of glucose, and the amount of urine increases as the glucose in the urine draws liquid with it.