What causes high blood glucose (sugar)?
High blood glucose, or high blood sugar, is called hyperglycemia. It is when your blood glucose is above 180 mg/dL.
High blood glucose (hyperglycemia) may happen when you:
eat too much food
take too little insulin or other diabetes medicines
are less active than usual
are stressed or more active than usual
This can happen slowly and may lead to a medical emergency if not taken care of.