Hi,
Well, an insulin overdose is a hypo - so it is very possible to do. Also elevated insulin levels cause a lot of other problems.
The 6ish end of your blood glucose levels is the one to stay at; 25 is very high and is going to do you a lot of harm, you really need to avoid any and all foods that get you to that level. Are you carb counting? Have you been given advice on insulin dosage and carb levels?
Read the various threads on this forum, and especially the low-carb one to get a flavour of how to control your blood sugars, and speak to your GP to get as much advice as possible.
Dillinger