Your child's occupational therapy was denied. The letter says "not medically necessary." You know that's wrong. The therapist recommended it. Your child needs it. The denial feels arbitrary, final, and designed to make you give up.

It's not final. "Not medically necessary" is the most common denial reason health insurers cite, and it's also the most reversible. Families win these appeals when they understand the process, meet the documentation requirements, and know where the system gives them power to push back.

Here's how to appeal a medical necessity denial: timelines, documentation, and what happens when internal appeals fail.

Understand Your Timeline

The clock starts the day you receive the denial letter. How long you have to appeal depends on whether your plan is governed by ERISA, which covers most employer-sponsored plans, or state law, which applies to individual marketplace plans and some government plans.

ERISA plans give you 180 days to file an internal appeal. The plan must respond within 30 days for urgent appeals, where waiting could seriously jeopardize your health, or 60 days for non-urgent appeals.

Non-ERISA plans follow state law. Timelines vary. Some states allow as few as 60 days to appeal, others give you 180. Your denial letter must state the deadline. If it doesn't, call the plan and ask.

Don't wait to figure out which type of plan you have. Your HR department can tell you if it's ERISA. If you bought the plan on the healthcare marketplace, it's likely governed by state law.

The 180-day window sounds generous. It's not. Getting a strong appeal letter from your provider takes time, and most families don't know what to ask for until they've already lost weeks.

The Letter of Medical Necessity Is the Linchpin

Most appeals succeed or fail on one document: the letter of medical necessity. This isn't the same as the initial referral or prescription. It's a detailed clinical justification that proves the treatment meets the insurer's medical criteria.

Your provider writes it, but you need to ask for it specifically. Most don't know what an appeal-ready letter requires. They'll write a vague paragraph restating that your child needs the service. That's not enough.

Ask your provider to include:

• Diagnosis with ICD-10 codes: the specific medical condition requiring treatment
• Functional limitations: what your child cannot do without the treatment, documented with assessments or clinical notes
• Treatment goals with measurable outcomes: not "improve fine motor skills" but "achieve independent feeding using adaptive utensils within 12 weeks"
• Why this treatment is medically appropriate: clinical rationale, citing treatment guidelines or peer-reviewed research if available
• Why alternatives won't work: if the insurer suggested a different treatment or no treatment, explain why those options don't meet the clinical need

If the denial cited specific criteria your child didn't meet, the letter must directly address those criteria. Don't guess. Look at the denial letter. If it says "treatment exceeds the frequency limit for this diagnosis," the letter needs to explain why higher frequency is clinically justified for your child's specific case.

Some providers balk at writing detailed letters. They're busy. They see it as administrative work that takes time from patient care. That's real, but it's also the difference between an appeal that reverses the denial and one that doesn't.

If your provider won't write the letter or doesn't know how, ask if their office has a case manager or patient advocate who handles appeals. Larger practices often do. If not, consider getting a second opinion from a provider who will document the medical necessity thoroughly.

Build Your Supporting Documentation

The letter of medical necessity is central, but it's not the only document. Compile everything that shows the treatment is medically appropriate and was properly authorized:

• Prior authorization approval: if the insurer initially approved the treatment, include that documentation. Denying something they already approved is harder to justify.
• Clinical notes: progress notes, intake assessments, or evaluations showing your child's condition and response to treatment
• Peer-reviewed research: if you can find journal articles supporting the treatment for your child's diagnosis, include them. This is especially useful for newer therapies or off-label use of established treatments.
• Treatment guidelines: professional associations often publish clinical practice guidelines. If the American Academy of Pediatrics or a relevant specialty organization recommends this treatment for this diagnosis, cite it.
• Functional assessments: standardized tests showing baseline function and deficits. If your child scored in the 5th percentile for fine motor skills, that's objective evidence the insurer can't easily dismiss.

You're not writing the appeal yourself. Your provider is. But gathering this documentation helps them write a stronger letter and shows the insurer you're not giving up after the first denial.

File the Internal Appeal

Most plans require you to use their appeal form. Call member services and ask them to send it, or download it from the plan's website. If there's no form, write a letter that includes:

• Your name, member ID, and contact information
• The patient's name and date of birth
• The date of the denial letter and the claim number
• A clear statement that you're appealing the denial
• The treatment or service that was denied
• The reason you're appealing, with the letter of medical necessity and supporting documents attached

Send the appeal by certified mail so you have proof of delivery. Keep copies of everything.

The insurer will assign your appeal to a reviewer, ideally someone with expertise in your child's condition. ERISA plans must use "appropriate" reviewers, meaning someone qualified to evaluate the clinical evidence. If the reviewer is a general practitioner and your child has a rare genetic condition, you can challenge the reviewer's qualifications as part of the appeal.

You have the right to request and review your full claim file during the appeal process. This includes the clinical criteria the insurer used to deny the claim, the credentials of the reviewer, and any internal communications about the denial. If you see evidence that the denial was based on cost savings rather than medical criteria, that strengthens your case for external review.

When the Internal Appeal Fails

If the insurer denies your internal appeal, you can request external review through an Independent Review Organization. This is available in 46 states and required for all ERISA plans.

External review is binding. If the IRO rules in your favor, the insurer must cover the treatment. The process is free to you. The insurer pays the IRO's fee.

You typically have 4 months from the date of the internal appeal denial to request external review. Some states allow longer. The denial letter must include instructions for how to request it.

The IRO reviews the same evidence you submitted during the internal appeal, plus any additional documentation you provide. The reviewer must be a clinical expert in the relevant specialty. They can't be the same person who denied your internal appeal and can't have a financial relationship to your insurer.

External review timelines vary by state and urgency. Urgent cases, where delay could seriously harm your child, are decided within 72 hours. Standard cases take 30 to 45 days.

ERISA Plans vs. Non-ERISA Plans: What's Different

ERISA plans, which cover most employer-sponsored coverage, follow federal rules:

• 180 days to file internal appeal
• 60 days for insurer to decide for non-urgent cases or 30 days for urgent cases
• External review available after internal appeal is exhausted
• You can sue in federal court if all appeals fail, but you can only recover the cost of the denied treatment, not damages for emotional distress or bad faith

Non-ERISA plans, which include individual marketplace plans and some state and local government plans, follow state law:

• Appeal timelines vary by state
• Some states allow you to skip straight to external review in certain cases
• If you win in external review, you may have additional remedies under state consumer protection laws

Your denial letter should state whether your plan is governed by ERISA. If it doesn't, ask. The distinction matters because it affects your timeline, your procedural rights, and what happens if you need to escalate beyond external review.

What If You Can't Wait for the Appeal

If your child needs the treatment immediately and waiting 60 to 180 days for an appeal decision would cause harm, you have two options:

Expedited appeal: ERISA plans must offer expedited review for urgent cases. The plan must decide within 72 hours if delaying treatment could seriously jeopardize your child's health or ability to regain maximum function. Call the plan and request an expedited appeal. You'll need a statement from your provider explaining why the delay is dangerous.

Pay out of pocket and appeal later: If you can afford it, pay for the treatment and continue the appeal. If you win, the insurer must reimburse you. This is a last resort. Most families can't front the cost. But it's an option if the treatment can't wait and the expedited appeal is denied.

Common Mistakes That Weaken Appeals

Submitting the same referral letter that was denied the first time. If the insurer already reviewed it and said no, sending it again won't change the outcome. You need a letter of medical necessity that directly addresses the denial reason.

Missing the deadline. Appeals filed even one day late are usually denied on procedural grounds, and you lose your right to external review. Mark the deadline on your calendar the day you receive the denial letter.

Not addressing the insurer's stated reason. If the denial says "treatment exceeds frequency limits," your appeal must explain why those limits don't apply to your child's case. A generic letter about why the treatment works won't move the decision.

Assuming the provider knows what to write. Providers are clinical experts, not appeals experts. Unless they've written successful appeal letters before, they may not know what documentation the insurer requires. Give them the denial letter, explain what the insurer wants to see, and offer to gather supporting research.

You're Not Fighting Alone

Medical necessity denials feel designed to intimidate families into giving up. The process is bureaucratic, the timelines are tight, and the documentation requirements aren't obvious unless you've done this before.

But the process is navigable. Families reverse these denials every day by understanding the timeline, getting a strong letter of medical necessity from their provider, and using external review when internal appeals fail. The insurer is betting you won't follow through. Following through is how you win.