It is hard to get your blood glucose levels down without taking more insulin. The only other options are drinking water or light activity, such as walking, can help. It would be good to find out why they are going high in the first place, then maybe you can avoid this happening too often in the future. It may be to do with your insulin amounts, or your diet, or hot weather, or if you're not feeling well. All these things can cause high blood glucose levels. I would suggest talking to your diabetes nurse or consultant to try and find out why this is happening and what you can do when it does. I hope this is of help to you.