What is a medical necessity denial?

A medical necessity denial means your insurance company claims the treatment your doctor ordered did not meet its clinical criteria. This does not mean your doctor was wrong — it means the insurer disagreed. You have the legal right to appeal.

Can I appeal a medical necessity denial?

Yes. You have a legal right to appeal any health insurance denial. Studies show over 40% of appeals are overturned when properly submitted. Most plans give only 30 to 180 days to file — act quickly.

How long do I have to appeal a health insurance denial?

Appeal deadlines are typically 30, 60, or 180 days from the denial letter date. Missing this deadline permanently forfeits your right to appeal. Check your denial letter or call your insurer immediately.

Is this template attorney-drafted?

Yes. This appeal letter template was drafted by an attorney with over a decade of insurance law experience. It is editable, includes a video tutorial, and is available as an instant download.

Why was my claim denied for out-of-network care?

Insurance companies deny out-of-network claims when the provider is not in their approved network. Many of these denials are wrongful — especially when care was urgent, when no in-network provider was reasonably available, or when you had no choice of provider in an emergency.

Can I appeal an out-of-network insurance denial?

Yes. You have the right to appeal, particularly if care was medically urgent, no in-network alternative was available, or the insurer failed to properly apply the No Surprises Act or state network adequacy rules.

What is the No Surprises Act?

The No Surprises Act protects patients from surprise bills for emergency care and for non-emergency care at in-network facilities by out-of-network providers when you had no meaningful choice of provider.

My insurance says my treatment is not covered — can I appeal?

Yes. Even when an insurer says a treatment is not covered or a policy exclusion applies, you can appeal. Many of these denials are based on ambiguous policy language or outright errors. An appeal forces the insurer to justify its reading of the policy.

What is a policy exclusion denial?

A policy exclusion denial means the insurer claims a specific clause in your policy excludes the treatment you received. These exclusions must be clearly stated — if the insurer cannot point to exact policy language, the denial may be wrongful and appealable.

Can I appeal a prior authorization denial?

Yes. You can appeal a prior authorization denial whether prospective, concurrent, or retrospective. Even if authorization was not obtained before care, you may have valid grounds — especially if care was urgent or the insurer's authorization process was unclear.

What if I had an emergency and could not get prior authorization?

Emergency care cannot legally require prior authorization. Cite the Emergency Medical Treatment and Labor Act (EMTALA) and your state emergency care laws in your appeal. Federal and state law require insurers to cover emergency stabilization regardless of prior authorization status.

How fast must insurers respond to a prior authorization appeal?

For urgent or ongoing care, you qualify for an expedited appeal — insurers must respond within 72 hours. For standard prior authorization appeals, deadlines are typically 30 days for pre-service decisions.

Can I appeal an experimental treatment denial?

Yes. Experimental or investigational treatment denials are among the most successfully appealed when the right evidence is presented. Insurers often apply outdated clinical criteria. A strong appeal presents published studies, clinical guidelines, and your physician's statement.

What evidence do I need to appeal an experimental treatment denial?

The strongest appeals include peer-reviewed clinical studies, published guidelines from major medical societies such as the AMA or ASCO, your treating physician's letter explaining why treatment is appropriate for your specific condition, and documentation showing the insurer's criteria are outdated.

What does denial code PR-1 mean?

PR-1 means Deductible Amount — Patient Responsibility. The insurer is applying the charge to your deductible. However, PR-1 denials are frequently incorrect — caused by calculation errors, timing issues, incorrect coordination of benefits, or provider and payer miscommunication.

Can I appeal a PR-1 deductible denial?

Yes. You can appeal if your deductible has already been met, if claims were processed in the wrong order, if there was a coordination-of-benefits error, or if the insurer incorrectly tracked your deductible accumulation.

What does denial code CO-167 mean?

CO-167 means the diagnosis code submitted does not justify the procedure billed. CO-167 denials are often caused by coding errors at the provider's billing office — not by a genuine lack of medical necessity.

How do I appeal a CO-167 diagnosis procedure mismatch denial?

Contact your provider's billing department to verify which codes were submitted. If codes were incorrect, ask the provider to resubmit. If codes were correct, file an appeal demonstrating the diagnosis supports the procedure using medical records and physician documentation.

What should I do first when my health insurance claim is denied?

Read the denial letter to find the denial reason and appeal deadline. Call your insurer for clarification. Gather your medical records, EOB, and insurance policy. File a formal internal appeal before the deadline — typically 30 to 180 days. Missing the deadline permanently forfeits your appeal rights.

Do I need a lawyer to appeal a health insurance denial?

No. Most health insurance denials can be appealed successfully without a lawyer using a well-structured appeal letter, your medical records, and your doctor's support. Attorney-drafted templates give you professional legal framing without the cost of retaining a lawyer.

What are the most important tips for winning a health insurance appeal?

Always file before the deadline. Address the specific denial reason rather than writing a generic letter. Get a detailed medical necessity letter from your treating physician. Include all relevant medical records. Cite clinical guidelines supporting your treatment. Send via certified mail and keep copies of everything.

What is the biggest mistake people make when appealing an insurance denial?

Writing a generic appeal that does not directly address the insurer's stated reason for denial. Each denial type requires different legal and clinical arguments. Match your arguments to the denial code and reasoning in your denial letter.

Are insurance companies using AI to deny claims?

Yes. Many major health insurers now use automated AI systems to review and deny claims — often without meaningful human review. These automated denials are legally challengeable through the standard appeal process.

What are the most common reasons health insurance claims are denied?

The most common reasons are: lack of prior authorization, treatment deemed not medically necessary, out-of-network provider, policy exclusion, diagnosis and procedure code mismatch (CO-167), deductible not met (PR-1), and experimental or investigational treatment classification. Most are appealable.

What is the difference between an internal and external insurance appeal?

An internal appeal is reviewed by your insurance company and is the required first step. An external appeal is reviewed by an independent organization — and its decision is legally binding on the insurer. Under the ACA, most health plans must offer external review after an internal appeal denial.

What Is a Letter of Medical Necessity? (And How to Get One That Actually Works)

May 11

Written By Tatiana Kadetskaya

If your health insurance claim was denied, this one document may be the most important thing standing between you and a reversal.

A letter of medical necessity is a formal statement from your treating physician explaining why a specific treatment, procedure, medication, or piece of equipment is medically required for your condition. It is not the same as a prescription, a referral, or a note in your medical chart. It is a targeted, standalone document written specifically to address an insurer's denial.

When written correctly, it forces the insurance company's reviewing clinician to engage directly with your physician's clinical reasoning — not just a billing code on a claim form.

When written poorly — or not written at all — it can be the single reason an otherwise valid appeal fails.

Why insurers require a letter of medical necessity

Insurance companies deny claims using automated systems that compare your diagnosis and procedure codes against internal clinical criteria. Those systems do not read your medical records, your treatment history, or your doctor's notes. They check whether your codes fit their criteria. When they don't match, the claim is flagged as "not medically necessary" — often before a human reviewer ever sees it.

A letter of medical necessity breaks that cycle. It introduces your physician's direct, documented clinical judgment into the appeal record. Insurers are required to address it. A reviewing clinician cannot simply ignore a signed letter from your treating doctor — they must explain why they disagree, which is a much higher bar than simply running a code through a filter.

This is why insurance reviewers pay close attention to how appeals are structured — and why a letter of medical necessity, properly written, shifts the burden back onto the insurer.

What a letter of medical necessity is NOT

Before explaining what it must include, it helps to understand what it is not:

It is not a prescription. A prescription says what treatment to provide. A letter of medical necessity explains why it is required.
It is not a referral. A referral authorizes a visit. A letter of medical necessity justifies coverage.
It is not a progress note or chart entry. Your medical records are evidence. A letter of medical necessity is an argument.
It is not a form your doctor fills out. Some insurers have standardized forms, but a standalone letter on physician letterhead is almost always more effective.

The letter is a persuasive clinical document. Its job is to connect your diagnosis, your treatment history, and your physician's judgment directly to your insurance policy's definition of medical necessity.

What a strong letter of medical necessity must include

1. Patient identification

Your full name, date of birth, member ID, and the specific treatment or service being requested or denied. The letter must be unambiguously tied to your specific claim.

2. Diagnosis and clinical findings

The specific diagnosis — with ICD-10 codes — and the clinical findings that support it. Lab results, imaging findings, examination findings, and symptom history should be referenced here. Vague statements like "patient has back pain" are not enough. Specific findings like "MRI confirms L4-L5 disc herniation with nerve root compression causing radiculopathy" are.

H3: 3. Treatment history — what was tried and failed

Insurers routinely deny claims on the basis that less intensive alternatives have not been tried. Your letter needs to document what was tried, for how long, and why it was insufficient. This is called the "step therapy" argument, and addressing it proactively is essential for most denials.

4. Why this specific treatment is necessary

This is the core of the letter. Your physician must explain — in clinical terms — why this specific treatment is the appropriate next step. This should reference:

The mechanism of the treatment and how it addresses the diagnosis
Clinical practice guidelines from relevant medical societies that support the treatment
Why alternatives are not appropriate for this patient specifically

5. Consequences of denial

What happens to the patient if this treatment is not provided? Specific, documented risks — functional decline, disease progression, emergency hospitalization — carry more weight than general statements. If delay creates urgency, this section supports an expedited appeal.

6. Citation of applicable guidelines

Any published clinical practice guidelines, peer-reviewed studies, or specialty society recommendations that support the treatment should be cited by name. The American Medical Association, specialty boards, and published clinical literature are the most authoritative sources.

7. Direct response to the denial reason

If the insurer has already issued a denial, the letter must address the specific reason stated. "Patient's diagnosis does not support this procedure" requires a point-by-point clinical rebuttal, not a general statement of necessity.

8. Physician signature on letterhead

The letter must be signed and dated, on the physician's official letterhead, with contact information for follow-up. Unsigned or undated letters are frequently rejected on procedural grounds.

How to ask your doctor for a letter of medical necessity

This is where most patients lose momentum. Many physicians are willing to write the letter but don't know exactly what the insurer needs — so they write something too general to be effective.

When you contact your doctor's office, give them:

A copy of your denial letter with the specific denial reason highlighted
A written request explaining that you need a letter of medical necessity for your insurance appeal — not a generic letter, but one that specifically addresses the insurer's stated denial reason
A list of the elements above, so their office knows what to include
Any relevant clinical guidelines that support your treatment, which you or your physician can research together

Many physician offices deal with insurance paperwork constantly. Giving them a clear framework makes the process faster and produces a better letter.

The letter of medical necessity and your appeal letter work together

A letter of medical necessity alone is not an appeal. It is evidence. Your appeal letter is the argument that ties the evidence to your policy language and demands a specific outcome.

This is why the two documents need to be coordinated. Your medical necessity appeal letter should reference the letter of medical necessity explicitly, quote from it where relevant, and frame it as clinical support for each point your appeal letter makes.

If you submit a letter of medical necessity without a well-structured appeal letter — or a strong appeal letter without a letter of medical necessity — you are fighting with half your evidence. Learn more about why insurers deny claims as not medically necessary and what a complete appeal requires →

Get your appeal letter and make your letter of medical necessity count

Our Medical Necessity Appeal Letter Template is built to work with your physician's letter. It includes structured placeholders that show you exactly where and how to incorporate your doctor's clinical findings, guidelines citations, and treatment history — so the two documents reinforce each other rather than sitting in a file separately.

Written by a licensed insurance attorney with 13 years of experience. Instant download. $29.

Get the Medical Necessity Appeal Letter Template — $29 →

Not sure if medical necessity is the right template for your denial? Take the 3-question quiz →

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Frequently Asked Questions

Who can write a letter of medical necessity?

Your treating physician is the most authoritative source. In some cases, a specialist, nurse practitioner, or physician assistant may also write one — but the treating physician's letter carries the most weight with insurance reviewers. The key is that the writer must have a direct clinical relationship with you and firsthand knowledge of your condition.

Does a letter of medical necessity guarantee my appeal will be approved?

No. A letter of medical necessity is the most important piece of evidence in most medical necessity appeals, but it must be paired with a well-structured appeal letter that ties it to your policy language. A good letter submitted with a poor appeal letter may still be denied.

How long should a letter of medical necessity be?

Long enough to cover all required elements, but not so long that key points get buried. One to two pages is typical. Dense, well-organized paragraphs are more effective than long narratives.

My doctor says they've already sent my medical records. Is that the same thing?

No. Medical records are raw documentation of your treatment history. A letter of medical necessity is a targeted argument written specifically for your appeal. Submitting records alone without a letter is one of the most common reasons medical necessity appeals fail.

What if my doctor refuses to write the letter?

It is uncommon for treating physicians to refuse, but if it happens, consider requesting it in writing and explaining the specific financial impact of the denial. You can also ask a specialist involved in your care. If you genuinely cannot obtain one, your appeal can still be filed — but it will be significantly weaker without it.

Tatiana Kadetskaya