Insurers may seek access to your medical records. Rather than just asking for access to the records which are relative to the accident, they often seek full access. The reason for this is often to look for information relating to conditions you may have had before the accident. This can be another way for them to reduce the offer they make for your injuries.
Your best bet if you are asked to sign any forms is to advise the adjuster of your intention to have your lawyer review the documents. This way, you are not jeopardizing your rights, and the insurance company knows they will have to deal with your attorney for all negotiations and discussions.