Independent Medical Review (IMR) in California Workers' Compensation

What is Independent Medical Review and how does it work?

Independent Medical Review (IMR) is California's statutory appeal process for any Utilization Review denial of workers' compensation medical treatment. Under California Labor Code §4610.5, when a UR conducted under California Labor Code §4610 denies, delays, or modifies a treatment request, the injured worker can appeal to IMR, which is administered by an independent organization contracted by the California Division of Workers' Compensation.

An independent physician — selected by the IMR organization, not by either party — reviews the worker's medical record, the treating physician's request, the UR denial reasoning, and the Medical Treatment Utilization Schedule. The physician decides whether the requested treatment is medically necessary. The decision is binding, with limited grounds for appeal to the Workers' Compensation Appeals Board.

How does the IMR process actually run?

The IMR process has four steps, each with a specific deadline. Missing a step generally means losing the appeal.

Step 1 — File the IMR request within 30 days of the UR denial

Under California Labor Code §4610.5, the worker has 30 days from receipt of the UR denial to file the IMR application. The application form is included with the UR denial letter and is also available from the California Division of Workers' Compensation at dir.ca.gov. The 30-day deadline is hard — extensions are not granted absent extraordinary circumstances. A worker who needs help should consult an attorney immediately upon receiving the UR denial.

Step 2 — Medical records are gathered and sent to the IMR organization

Within 15 days after the IMR request is accepted, the insurer must provide the IMR organization with the worker's medical records relevant to the treatment dispute — including the treating physician's request, prior medical records, and the UR denial documentation. The worker (or the worker's attorney) can also submit additional medical evidence directly to the IMR organization.

Step 3 — Independent physician review

The IMR organization assigns an independent physician with relevant clinical expertise. The physician reviews the medical record, the treating physician's recommendation, the UR denial reasoning, and the Medical Treatment Utilization Schedule. The reviewing physician does not examine the worker in person — IMR is a records-based review. The decision must be issued within 30 days of receipt of the medical records (sooner for expedited reviews of urgent treatment).

Step 4 — The IMR decision is binding, with narrow appeal rights

The IMR determination is binding on both parties. Grounds for appeal to the WCAB are limited to specific procedural failures — for example, that the IMR was conducted without sufficient medical evidence, that the IMR organization acted in excess of its authority, that the determination was procured by fraud, or that there was a material conflict of interest. A worker who wants to challenge the IMR decision must file a Petition for Reconsideration within 25 days of service by mail (or 20 days from electronic service) under California Labor Code §5903.

What does the UR denial letter actually mean?

A UR denial letter is one reviewing physician's decision that, based on the medical record and the MTUS, the requested treatment is not medically necessary. It is not a final ruling on the worker's care — the worker can still pursue alternative treatments, escalate to IMR, or in some cases proceed with the treatment out-of-pocket and litigate reimbursement. Critically, a UR denial does not relieve the insurer of its obligation to authorize up to $10,000 in initial treatment within one day of the completed DWC-1 under California Labor Code §5402(c).

The UR denial letter must include specific information: the clinical reasons for the denial, the name and credentials of the reviewing physician, the MTUS guideline citations relied on, and instructions for filing an IMR appeal. A UR denial that omits any of these is procedurally defective and may be challenged directly at the WCAB.

What if the UR denial keeps getting issued after each request?

A pattern of repeated UR denials — particularly for treatment a QME or AME under California Labor Code §4062.2 has stated is necessary, or for treatment expressly supported by the MTUS — can be evidence of bad faith. Unreasonable delay in providing medical care can support a 25% penalty on unreasonably delayed benefits under California Labor Code §5814. If an employer's repeated treatment denials are tied to a retaliatory motive against the claim, a separate California Labor Code §132a petition may apply, providing reinstatement, lost wages, an increase in compensation up to $10,000, and costs up to $250.

What protections does the worker have during the IMR process?

The worker's right to medical treatment under California Labor Code §4600 continues during the IMR process — for any treatment not subject to the specific UR denial. The right to choose a treating physician within the Medical Provider Network is preserved. Immigration status does not affect the worker's IMR rights: California Labor Code §3351 extends California workers' compensation coverage including IMR to every California worker, and California Labor Code §244 prohibits the employer from threatening immigration-status reporting as retaliation. Under California Labor Code §5811, the worker is entitled to a qualified interpreter at any related WCAB hearings.