What is prior authorization — and why are denials so common?
Prior authorization (PA) is the process insurers use to review a proposed treatment, procedure, medication, or medical device before they agree to pay for it. If the insurer denies prior authorization, your provider cannot proceed expecting coverage — which means either the treatment gets delayed, you pay out of pocket, or you appeal.
PA was originally designed to catch unnecessary or high-cost procedures. In practice it has become a routine bottleneck: the American Medical Association's 2024 physician survey found that 94% of physicians report PA delays patient care, and 33% report PA has led to a serious adverse event for a patient. Medicare Advantage plans alone denied roughly 4.1 million PA requests in a single year, according to KFF.
Denial reasons cluster into a few patterns:
- Medical necessity not established — the insurer's reviewer determined the clinical evidence in your record doesn't meet the plan's criteria for coverage.
- Step therapy / fail-first requirements — the plan requires a cheaper alternative be tried and fail before approving the requested treatment.
- Experimental or investigational exclusion — the plan classifies the treatment as not yet proven, even when clinical guidelines and major medical society statements support its use.
- Missing documentation — the prior auth submission lacked specific clinical notes, imaging, lab results, or provider attestations the plan requires. This is the easiest category to fix.
- Out-of-network provider — the requested treatment is in-network in principle but the specific provider is not, or the site of service is classified wrong.
The critical insight: PA denials often turn on documentation, plan rules, and deadlines. The reason appeals matter is simple: most denied claims are never appealed, so many patients never get a second review of the clinical evidence, criteria, or paperwork the plan relied on.
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Start my prior-auth appeal — free analysisYour legal rights on prior authorization
Affordable Care Act (ACA) Section 2719
Every ACA-compliant plan must provide a written internal appeal process and, if the internal appeal is denied, an independent external review by a medical reviewer not employed by the insurer. The external reviewer's decision is binding on the insurer. Urgent prior-auth situations qualify for expedited review with a decision within 72 hours.
Federal PA transparency rule (CMS-0057-F)
Starting in 2026, Medicare Advantage, Medicaid managed care, CHIP, and ACA marketplace plans are required to publicly report prior-authorization metrics including approval rates, denial rates, and average processing times. By 2027 they must use electronic PA APIs that eliminate fax-based submissions. These rules create strong leverage — if your insurer misses PA decision deadlines, the service is considered approved by default under many plans.
ERISA “full and fair review”
Employer-sponsored plans are governed by ERISA, which requires a “full and fair review” of any denied claim — including prior-auth denials. You have 180 days from the denial date to file an appeal. The plan must give you the specific clinical guidelines and criteria used to deny, and you can request and review the complete claim file.
State prompt-decision laws
Many states have their own laws requiring insurers to decide PA requests within 24–72 hours for urgent cases and 7–15 days for standard cases. If the insurer misses the deadline, the request is deemed approved in many states. Check your state insurance department's PA regulations.
Step-by-step: appealing a prior authorization denial
Read the denial letter and identify the specific reason
Every PA denial must state the specific medical-necessity criteria, plan provision, or clinical policy the insurer relied on. Find that exact reason — it dictates everything that follows. A denial for "not medically necessary" requires different evidence than one for "experimental" or "step therapy not met". Read the denial letter word by word and note the specific criteria cited.
Request a peer-to-peer review within 24–72 hours
Your prescribing physician can request a peer-to-peer (P2P) review — a direct phone call between your doctor and the insurer's medical reviewer (another physician or nurse). P2P can be the fastest path before any written appeal is needed. Call the number on your denial letter. If the denial is urgent (e.g. cancer treatment), request expedited P2P — most plans respond within 24–72 hours for urgent cases.
Gather your medical-necessity evidence
If peer-to-peer fails or is unavailable, build the written appeal file. You need: (a) the original PA submission and denial letter, (b) all relevant clinical notes, labs, imaging, and prior treatment records, (c) clinical guideline citations from major medical societies that support the requested treatment for your diagnosis, (d) peer-reviewed literature supporting efficacy for your clinical situation, (e) a medical-necessity letter from your treating physician that directly addresses each denial reason cited.
File the formal internal appeal within 180 days
Submit your written appeal within 180 days of the denial (ACA / ERISA minimum). Include a cover letter summarizing why each denial reason is incorrect, the evidence file you gathered, and a request for expedited review if the situation is urgent. Send by certified mail with return receipt or via the insurer portal with screenshots of the submission confirmation. The insurer must respond within 30 days for pre-service claims and 60 days for post-service claims.
Escalate to independent external review if the internal appeal is denied
Once internal appeals are exhausted, ACA gives you the right to independent external review by a medical reviewer with no financial tie to the insurer. For ACA plans, the external review is typically administered by the state insurance department or a federally-contracted Independent Review Organization (IRO). Submit within 60–120 days of the final internal denial (exact window varies by state and plan type). The IRO decision is binding on the insurer.
Track every deadline and keep copies of everything
Prior-auth appeals are unforgiving on deadlines. Missing the 180-day internal appeal window or the external review window waives the right entirely. Maintain a written log of every call (date, time, person you spoke with, reference number), keep copies of every letter and portal submission, and set calendar reminders for each deadline. Your appeal file may need to be referenced months later during external review.
What to include in a medical-necessity appeal letter
The single most important document in a prior-auth appeal is the medical-necessity letter from your treating physician. A well-crafted letter should include:
- Your diagnosis with ICD-10 codes and the specific clinical findings that support it (lab values, imaging findings, symptom duration).
- A statement of why the requested treatment is medically necessary for your specific presentation — not a generic endorsement.
- Direct address of each denial reason the insurer cited, with counter-evidence. If they said "not medically necessary," cite the specific clinical guidelines and your clinical findings that satisfy their criteria.
- Clinical guideline citations from major medical societies (ACOG, AAP, NCCN, ACC, etc.) that support the treatment for your condition.
- Peer-reviewed literature supporting efficacy in your clinical situation — at least 3–5 recent citations where possible.
- History of prior treatments tried and why they failed or were inappropriate (crucial for step-therapy denials).
- The risk of delay or denial — what happens clinically if this treatment is not approved. This is especially important for urgent cases.
- A request for peer-to-peer review if not already done, and expedited review if the situation is urgent.
Common mistakes that sink PA appeals
Skipping peer-to-peer review
A peer-to-peer call can sometimes resolve issues faster than a written appeal. Consider it early unless the deadline has passed.
Generic medical-necessity language
A letter that says "this treatment is standard of care" without citing guidelines and tying them to your specific clinical findings will lose. Insurers need to see your diagnosis, your labs, your imaging, and the specific criteria you meet.
Missing the 180-day window
The appeal clock starts the day you receive the denial — not the day the treatment was denied. Miss this window and you lose the right to appeal under both ACA and ERISA. File early even if you're still gathering evidence; you can supplement later.
Not requesting expedited review for urgent cases
If your health is at risk from delay (cancer treatment, active flare of chronic condition, etc.), request expedited review. Insurers must respond within 72 hours. Standard review windows can take weeks — unacceptable for urgent care.
Submitting without your doctor's active participation
The insurer's reviewer will call your doctor's office for clarifications. If your doctor's staff isn't prepped to respond, the appeal can fail on a missed callback. Coordinate with your doctor's office before submitting — make sure they know an appeal is in flight and to route insurer calls to the right person.
What to do if the internal appeal is denied
Internal appeal denied? You still have multiple paths:
- Independent external review (ACA right). A medical reviewer with no financial relationship to your insurer reviews the case. Their decision is binding — if they overturn, the insurer must approve. External review overturn rates are meaningfully higher than internal appeal rates because the reviewer doesn't work for the insurer.
- State insurance department complaint. Particularly effective if the insurer missed a statutory deadline or ignored state prompt-decision laws. Many states have consumer advocate offices that will intercede directly.
- ERISA civil action (employer plans). For employer-sponsored plans under ERISA, if internal appeals are exhausted, you can bring a civil action in federal court challenging the denial. Most cases settle once filed; few reach trial.
- HHS / CMS complaint for Medicare Advantage. Medicare Advantage plans have specific federal oversight. Complaints to 1-800-MEDICARE or via medicare.gov trigger direct CMS investigation.
- Consult a healthcare attorney. For high-dollar or life-threatening denials, an attorney can often resolve the case through a demand letter that cites ERISA, state consumer protection laws, and medical necessity — before litigation is even filed.
Your prior auth was denied. We can help.
Lysco analyzes your denial, tells you exactly what the insurer needs, and drafts a medical-necessity support letter your doctor can review, sign, and submit — tailored to your plan's specific criteria.
Start my appeal — free analysisInformational only — not legal or medical advice. Individual outcomes depend on the specifics of each case.
Related guides
This guide is informational and does not constitute legal or medical advice. Federal and state PA rules change; consult current regulations and, where appropriate, licensed professionals for your specific situation. Lysco is not a law firm and does not represent you in appeals or regulatory proceedings.