A doctor refers a patient to a specialist or another physician who can take care of a condition.
The primary care is submitting a request to the patient's insurance to cover a visit(s) to a specialist for a condition.
Unfortunately, the requirements are changing year-to-year (sometimes sooner), so we're not able to provide an adequate list of all insurances requiring referrals. The best option to avoid having to reschedule is to call your insurance prior to the visit to ensure a referral isn't required.
Insurance referrals are required to have start and end dates, as well as the number of allotted visits.