By making a personal injury claim, you are asking the insurance company for the person who caused your injuries to pay you for your damages. In the most generous view of insurance companies, in order to fairly compensate you, the will need to do a full invesitigation of your claim. Of course, we normally see that this investigation is not as impartial as it should be. Nevertheless, when you make a claim, you open a window into parts of your life you would ordinarily consider private.
One example is your medical history. For instance, if you are claiming that you have an injury to the muscles in your neck, it makes sense for the insurance company to verify that you weren’t treating for the same thing before the accident. Obviously, they are not required to pay you to get physical therapy for your neck if it was necessitated by a prior, chronic neck problem. There is no way to know if you had a prior neck problem without examining your medical history.
The analysis of what information the insurance company is entitled to review really comes down to what they may receive should your case enter litgation, and further, what they would be allowed to present to a jury. The scope is extremely broad. However, in some circumstances, items that could in no way be related to an auto accident, or would not be allowed into evidence in a trial, can be withheld.