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Medical treatment: your doctor, the MPN, UR and IMR

By Richard Vaughn CPCU, ARM, AIS. Reviewed November 8, 2026. Richard is an insurance professional, not an attorney. This page explains the law; it is not legal advice.

What the employer must provide

Your employer is required to provide all medical, surgical, chiropractic, acupuncture and hospital treatment, including medicines, supplies and prosthetic devices, that is reasonably required to cure or relieve the effects of the injury (Labor Code §4600(a)). "Reasonably required" means consistent with the medical treatment utilization schedule (MTUS), the evidence-based guidelines the Division of Workers' Compensation adopts (Labor Code §4600(b)). There is no copay, no deductible and no time limit; what limits treatment is the guideline, not the calendar. Treatment that goes beyond the guidelines needs other medical evidence from your doctor to support it.

You are reimbursed for travel to and from medical appointments at the state mileage rate, plus tolls, and for a day of temporary disability for each day of wages lost attending an examination the claims administrator or a judge requires (Labor Code §4600(e)).

Who chooses the doctor

For the first visit after an injury, the employer or its medical provider network usually chooses the physician. The exception is predesignation: if, before the injury, you told your employer in writing that your personal physician should treat you for any work injury, you had non-work health coverage on the date of injury, and the doctor is your regular primary care physician who agreed in advance to be predesignated, you can be treated by that doctor from the start (Labor Code §4600(d)). Predesignation has to be done before you are hurt; it is a form worth filing on your first day of work.

If your employer has no MPN, you can choose your own treating physician in a reasonable geographic area 30 days after you reported the injury (Labor Code §4600(c)). Almost every insured employer has an MPN, so the network rules below are the ones that usually apply.

Inside a medical provider network

A medical provider network (MPN) is a group of doctors assembled by the insurer or self-insured employer and approved by the Division of Workers' Compensation for four years at a time (Labor Code §4616(b)). It has to include physicians who mainly treat work injuries, enough of the right specialties for the injuries common in your industry and area, and treatment reasonably available at reasonable times (Labor Code §4616(a)). The network must post an online roster of its doctors, updated at least quarterly, and staff a toll-free line of medical access assistants, 7 a.m. to 8 p.m. Monday through Saturday, whose job is to help you find a doctor (Labor Code §4616(a)(4), (5)).

Your rights inside the network are specific. After the first visit you may change to any other physician in the network, and your employer must tell you that in writing, along with how to find the roster (Labor Code §4616.3(b)). If you dispute the diagnosis or the treatment plan, you can get a second opinion from another network doctor and, if still in dispute, a third (Labor Code §4616.3(c)). The choice of doctor is based on the specialty the injury needs, and if no network doctor can provide an approved treatment, an outside specialist can be allowed case by case (Labor Code §4616.3(d)).

Utilization review: the approval step

Your doctor does not simply order treatment. For anything beyond the first 30 days of basic care, the doctor sends a Request for Authorization (RFA) to the claims administrator, which runs it through utilization review (UR). UR is the process the claims administrator uses to decide whether a requested treatment is medically necessary under the MTUS (Labor Code §4610). Within the first 30 days after the injury, treatment of an accepted body part by an MPN or predesignated physician is exempt from prospective review, except for surgery, imaging other than x-rays, psychological treatment, home health care, non-formulary drugs and equipment over a set cost (Labor Code §4610(b), (c)).

The rules protect you in four ways. Only a licensed physician may modify or deny a request on medical grounds; a nurse or claims examiner may approve but not deny (Labor Code §4610(g)). Decisions must follow the MTUS and the drug formulary, and the criteria used to deny must be disclosed (Labor Code §4610(g), (h)). The timeframes are fixed: five working days from the request for a prospective decision, no later than 14 days after the doctor's recommendation; 72 hours for an expedited request where delay threatens your health; 30 days for retrospective review of treatment already given (Labor Code §4610(i)). And a denial must be in writing to you within two working days, must state the reasons and the clinical basis, and must come with the form to request independent medical review (Labor Code §4610(i)(4), §4610.5(f)).

A UR denial stands for 12 months for the same treatment from the same doctor unless a documented change in your condition supports a new request (Labor Code §4610(k)). That rule is why the IMR deadline matters.

Independent medical review: the appeal

If UR modifies, delays or denies a treatment request, the only way to challenge the medical-necessity decision is independent medical review (IMR) (Labor Code §4610.5(e), §4062(b)). You, or your doctor on your behalf, request it by signing and returning the one-page IMR application that must accompany the denial letter, within 30 days of the date the decision was served (10 days for a drug formulary dispute) (Labor Code §4610.5(h)). If the claims administrator failed to send the application, the deadline does not start until it does.

The review is conducted by an independent physician reviewer under contract to the Division of Workers' Compensation. The reviewer applies the MTUS and the drug formulary, peer-reviewed evidence, nationally recognized standards and expert opinion, and can consider treatments likely to benefit a patient when the guideline treatments have not worked (Labor Code §4610.5(c)). The claims administrator must send the records and its reasons within 10 days of assignment, and your treating doctor can submit the recommendation and supporting material (Labor Code §4610.5(l), (f)(3)). The claims administrator can end the review at any point by authorizing the treatment in writing (Labor Code §4610.5(g)).

The IMR decision decides the medical question. Disputes about whether the injury is work-related, or which body parts are covered, are not UR or IMR questions; they go to a qualified medical evaluator, covered on the QME and AME page.

When the dispute is with the doctor, not the insurer

If you disagree with your MPN doctor's diagnosis or treatment plan, the route is the second and third opinion inside the network (Labor Code §4616.3(c)), not IMR. If you disagree with your treating doctor about whether you can work, whether you are permanent and stationary, or how much permanent disability you have, the route is a written objection within 30 days of the report (20 if you have an attorney) and a request for a qualified medical evaluator panel (Labor Code §4062(a)). Which route applies depends on what is in dispute: medical necessity of a treatment goes to UR and IMR; diagnosis or plan inside the network goes to second and third opinion; work status and disability go to a QME.

Questions people ask

Richard Vaughn CPCU, ARM, AIS

Richard Vaughn spent 35 years in commercial property and casualty insurance, most of it in workers' compensation: running a self-insured group, auditing premiums, and implementing claims systems for carriers and third-party administrators. He is not an attorney. dickvaughn.com