How to Appeal an HMO Claim Denial

When an HMO denies a claim or refuses to authorize a service, members have federally and state-protected rights to challenge that decision through a structured appeal process. This page explains how internal and external appeals work, the timelines that govern each stage, the scenarios that most commonly trigger denials, and the criteria that determine which appeal pathway applies. Understanding the process before filing can materially affect the outcome.

Definition and scope

An HMO claim denial is a formal determination by a health plan that a requested service, item, or payment does not qualify for coverage under the plan's terms. Denials fall into two broad categories: adverse benefit determinations (coverage or payment refused after service) and prior authorization denials (coverage refused before service is rendered). Both are subject to appeal rights established under the Affordable Care Act (ACA, 42 U.S.C. § 18001 et seq.) and, for employer-sponsored plans, the Employee Retirement Income Security Act (ERISA, 29 U.S.C. § 1001 et seq.).

Federal regulations at 29 C.F.R. § 2560.503-1 set minimum claims and appeals standards for ERISA-governed plans. State-regulated HMOs — those sold in the individual and small-group markets — are subject to state insurance department rules that must meet or exceed ACA requirements. Members enrolled in Medicaid HMOs operate under a parallel appeals framework governed by 42 C.F.R. Part 438, administered by the Centers for Medicare & Medicaid Services (CMS). The practical scope of appeal rights therefore depends on whether the plan is ERISA-governed, state-regulated, or a public program.

For a broader orientation to consumer rights within HMO structures, the hmoauthority.com home resource outlines the full landscape of coverage and regulatory topics.

How it works

The appeal process follows a sequential structure with mandatory deadlines at each stage.

Stage 1 — Internal Appeal

The member (or an authorized representative) submits a written request challenging the denial. Under 45 C.F.R. § 147.136, non-grandfathered plans must:

Acknowledge receipt of the appeal within a reasonable time frame.
Complete an urgent/expedited appeal (when the standard timeframe would seriously jeopardize health) within 72 hours.
Complete a pre-service appeal (for services not yet rendered under non-urgent circumstances) within 30 calendar days.
Complete a post-service appeal (for reimbursement of already-delivered care) within 60 calendar days.

The plan must conduct the review using a qualified reviewer who was not involved in the initial denial and who has appropriate medical or clinical expertise. Plans must provide free access to all documents relevant to the decision upon request.

Stage 2 — External Review

If the internal appeal is upheld, members of non-grandfathered plans have the right to request an independent external review. Federal standards under 45 C.F.R. § 147.138 require states to maintain an accredited Independent Review Organization (IRO) system or operate under the federal external review process administered by the Department of Labor (DOL) and the Department of Health and Human Services (HHS). External reviewers render a binding decision. The expedited external review timeline is 72 hours; the standard timeline is 45 calendar days.

HMO external review rights and HMO consumer protections and grievance procedures provide deeper analysis of each stage's procedural requirements.

Common scenarios

Denials that most frequently trigger appeals include the following:

Out-of-network service without authorization — A member receives care from a provider outside the HMO network without a plan-approved exception. HMO network rules are strict; out-of-network care in an HMO explains when exceptions apply.
Medical necessity denial — The plan determines the requested service does not meet its definition of medical necessity. This is the most litigated denial category in external review proceedings.
Referral not obtained — A member sees a specialist without a required primary care physician referral. How HMO referrals work details the referral requirement.
Formulary exclusion — A prescribed drug is not on the plan's approved formulary. HMO prescription drug coverage and formularies covers formulary exception processes separately.
Emergency care coding disputes — The plan reclassifies a billed emergency visit as non-emergent after the fact, triggering a retroactive denial. Emergency care under an HMO plan explains the "prudent layperson" standard that governs these situations.
Experimental or investigational treatment — The plan excludes a requested therapy as not proven effective under its benefit design criteria.

Decision boundaries

Choosing the correct appeal type and pathway depends on three factors: plan type, urgency, and whether internal remedies are exhausted.

Factor	Internal Appeal	External Review
Who decides	Plan's independent clinical reviewer	Accredited IRO, not affiliated with the plan
Binding on plan	Plan may uphold denial	IRO decision is binding
Deadline (standard)	30–60 days depending on service type	45 calendar days
Deadline (expedited)	72 hours	72 hours
Cost to member	None permitted	None permitted (federally required)

ERISA-governed employer plans add a further layer: members who exhaust internal remedies and external review may still pursue civil action under ERISA § 502(a), which preempts state-law remedies. State-regulated individual and small-group HMO members retain state-law remedies, including complaints to state insurance regulators, even after external review. ERISA and HMO plans addresses how federal preemption affects litigation options.

Medicaid HMO enrollees follow a distinct track: they may request a State Fair Hearing under 42 C.F.R. § 431.200 in addition to or instead of the plan's internal appeal, with continuation of benefits during the hearing if the request is filed within 10 days of the denial notice.

References

The law belongs to the people. Georgia v. Public.Resource.Org, 590 U.S. (2020)