Unless you had a lot to drink just before you drove and your reading was going to go up a lot, you will be under the legal limit.
you do not have to tell your insurance company at this time.
Some policies say you must tell them when you are convicted, others simply say to tell them at renewal.
Check your policy, just in case there is something obscure in there requiring you to disclose being under investigation, but as you had an accident they will presumably be made aware of that, if not by you then by the other parties insurance. The other party may have put on his claim form that you blew a positive breath test at the scene. (But that is not evidence, just an indicator)