Definition
Referring Physician
A referring physician is the physician or other practitioner who sends a patient to another provider, or orders a service such as imaging, laboratory tests, medical equipment or home health care, and is named on the resulting claim.
1 min readReviewed September 14, 2026
Also known as: Referring provider, Ordering provider, Ordering physician, Referral source
Key facts
- Claim data
- Referring or ordering provider name and NPI
- Medicare requirement
- Ordering and referring providers must be enrolled in or opted out of Medicare
- Order-and-refer-only enrollment
- Form CMS-855O
- Self-referral law
- Physician Self-Referral Law (Stark Law), Section 1877 of the Social Security Act
What is a referring physician?
A referral moves a patient from one clinician to another: a primary care physician sends a patient to a cardiologist, or a surgeon orders physical therapy after an operation. The practitioner who initiates the service is the referring or ordering provider, and many claims must identify that person as well as the provider who performed the service.
Despite the name, the referring provider does not have to be a physician. Depending on the service and the payer, nurse practitioners, physician assistants and other practitioners can order and refer.
How Medicare ordering and referring rules work
Medicare applies specific rules to ordered and referred services:
Home health certification has its own rules. Since the CARES Act of 2020, nurse practitioners, clinical nurse specialists and physician assistants can certify eligibility for Medicare home health services, not only physicians.
- Claims for clinical laboratory services, imaging, durable medical equipment and home health services must name the ordering or referring provider and NPI.
- That provider must have an approved Medicare enrollment or a valid opt-out on file, or the claim can be denied.
- Practitioners who do not bill Medicare can enroll only to order and refer, using form CMS-855O.
- CMS publishes a public file of practitioners eligible to order and refer.
Why referring physicians matter
Referrals drive specialist volume, hospital admissions and procedure demand. Health systems study referral patterns to reduce leakage to competitors, device and diagnostics companies target the physicians who order tests and procedures, and specialty practices build relationships with referral sources.
Referral relationships also carry legal risk. The Stark Law bars physicians from referring Medicare patients for designated health services to entities with which they have a financial relationship unless an exception applies, and the federal Anti-Kickback Statute prohibits paying for referrals.