When you have low blood sugar (under 67 mg/dL), there are specific things you can do to raise blood sugar back to normal (70-99 mg/dL); but it’s not so easy when you have high blood sugar. For anything over 300 mg/dL, I would definitely phone your on-call advice nurse and ask for help. For blood sugars of 400+, don’t hesitate to go to the ER! They will give you regular insulin along with fluid and electrolyte replacement.
When your blood sugars are really high (200-300 mg/dL), it would be best to fast and only drink water or broth. But if you’re hungry, what you need to eat is pretty much protein and healthy fat—NO carbs, not even vegetables—until your blood sugar goes down. Use plain half-and-half in your coffee instead of any commercial creamer, though the best creamer is pure unsweetened heavy whipping cream. Drink enough water to stay hydrated but don’t overdo it as water flushes electrolytes out which need to be replaced (sodium and potassium). You can walk—gently—but no aggressive exercise until your blood sugar is back down. Definitely NO exercise if your blood sugar is over 250 mg/dL. You should discuss exercise with your healthcare provider, anyway.
Of course, the best thing is to prevent high blood sugars by not eating foods that raise your blood sugar. Don’t even buy them! At [your grocery source], stay away from highly processed grain products (no pasta, cereals, chips, crackers, cheese puffs, etc.)—get real cheese instead (cheddar cheese, mozzarella cheese sticks, full-fat cream cheese) and no starchy vegetables (cauliflower instead of potatoes). Get as much of the non-starchy vegetables as possible—green beans, spinach, kale, lettuce, cabbage, bok choy, cucumbers, green bell pepper, broccoli, asparagus, Brussels sprouts, zucchini. And, of course, lots of eggs! Get berries (strawberries, blackberries, blueberries, raspberries). If you can get virgin coconut oil and extra virgin olive oil (in a dark bottle), please do so! If/when you eat meat, you can have ground beef or turkey, uncured beef or turkey hot dogs, uncured turkey bacon, and chicken. Hope this helps.