With blood sugar this high, you must drink plenty of fluids. Non sweetened. Water and unsweetened tea are ok. Do not take any carbohydrate containing foods until your blood sugars come down. If your numbers don't come down within a few hours you should go to the ER.
You will need to see your doctor. maybe you need to start on insulin to help control your blood sugars.
A low carbohydrate diet, and low glycaemic index foods may help you in controlling blood sugars. If you can't do it with diet and exercise, insulin is very helpful.
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Blood sugars averaging 160 mg/dl are high and 309 mg/dl extremely high. Better control and management of your diabetes is needed. Do you know what these are and what you need to do? In any case, if you blood sugars remain above 200 mg/dl I suggest you go to the nearest ER for treatment. Good luck -