Is 5000mcg of biotin too much for a type 1 diabetic to take? and does the brand of biotin matters?

Check with your dr: It's best to let your doctor know that you're interested in taking biotin, especially if s/he are managing you for diabetes type 1. For someone who is nondiabetic that amount is not a problem. However in your particular situation, your doctor is probably monitoring you very carefully. So, they need to know all the supplements that you're taking. Then you can work together as a team! as a sidenote, your clinical pharmacist can also help you with this.