As a rule of thumb, if BG is really high two hours after a meal, should I inject more insulin to get me in good shape until the next meal?
It is not a good idea to take insulin two hours after a meal because the insulin you took before the meal may still be working to lower your blood glucose and it can put you at risk for lows later on. Also, most insulin dosing is based upon pre-meal numbers not after-meal numbers, so if you use the same dosing rules that you normally use, you will end up giving yourself too much insulin. If you are seeing that there is a pattern of highs after your meals, start checking more often both before and 3 hours after meals (this gives the insulin enough time to work to lower your blood glucose). Write down the numbers and see if there are patterns to the highs. Talk to your doctor or diabetes educator to see if there is a need to change your insulin pre-meal dosing. Also, to make sure you are counting your carbs correctly, it may be a good idea to take 3 days of detailed blood glucose, food and carb counting records to a dietitian for review. If you are off on your carb counting or for some reason forget to take your pre-meal insulin, talk to your diabetes team about how to safely take a correction dose 3 hours after eating.