When my mother-in-law had this during radiation treatment that included steroids to reduce swelling, it resolved as treatment ended and steroids were tapered. Her oncologist had failed to have her monitored daily as the radiation protocol recommended, and we had no clue until she had a seizure. Now we know the protocol for treating steroid induced diabetes is generally monitoring plus treatment with medication or insulin, depending on patient response.

If your husband's blood sugar levels stay above 250-300 even after increased glipizide & reduced steroids, he is possibly at risk for ketoacidosis Since the meter doesn't check for this, ketone testing might be needed. So, if the levels stay up, you might want to ask the doctor...

I understand the difficulty you face with offering food and drink - but additional water is highly recommended to reduce both ketones & effects of the diabetes and radiation.

Is he willing and able to drink more water?
Sue