how-to
How to Write a Letter of Medical Necessity for Medicare
Last Updated: November 10, 2026
Quick Summary
A letter of medical necessity is a written statement from your doctor explaining why a specific test, treatment or service is needed. To write one for Medicare, the doctor should include your identifying details, the diagnosis with its ICD-10 code, the requested service, a clinical rationale and references to the supporting records.
- Your name, date of birth and member ID must match your insurance card exactly.
- Include the diagnosis with its correct ICD-10 code so it matches the request.
- List prior treatments with dates and outcomes to show less intensive options were tried.
- Tie each statement to an attached record by type and date.
- An unsigned or undated letter can be returned without review.
Table of Contents
- What a Letter of Medical Necessity Does for Medicare Claims
- What to Include in a Letter of Medical Necessity
- Step-by-Step: Writing the Letter
- Letter of Medical Necessity Example for a Medicare Request
- Letter of Medical Necessity Template PDF: What to Look for
- How to Ask Your Doctor for a Letter of Medical Necessity
- Handling a Denial and Filing an Appeal
- Your Next Step: Confirm Your Coverage Before You Submit
- Frequently Asked Questions
What a Letter of Medical Necessity Does for Medicare Claims
A letter of medical necessity is a written statement from your doctor that explains why a specific test, treatment, device or service is needed for your health. Medicare uses it to decide whether a service is "reasonable and necessary" under its coverage rules (Medicare Coverage of Items and Services). This letter often comes up when a Medicare Advantage plan asks for extra proof before it approves a request.
Here is the key point: the letter does not replace your doctor's medical records. For a deeper explanation of how Medicare Advantage prior authorization works, read the full guide. It summarizes them. It tells the reviewer what condition you have, what the provider recommends, and why the recommendation fits your situation.
A strong letter helps reduce delays. A weak or vague letter can lead to a denial, which means more paperwork and more time waiting for care.
What to Include in a Letter of Medical Necessity
Every letter should answer three questions: who you are, what you need, and why you need it. Most reviewers look for a clear, complete set of details on the first read.
Plan to include:
- Your full name, date of birth and Medicare or plan ID number
- The diagnosis, with the correct ICD-10 code
- The specific test, treatment or item being requested
- A clinical reason that links your diagnosis to the request
- A list of the records attached to support the request
Patient Demographics and Diagnosis Codes
Start with the basics. Your name, date of birth and member ID must match your insurance card exactly. A small mismatch can slow the review.
Next, list the diagnosis with its ICD-10 code. ICD-10 is the standard coding system doctors and insurers use to describe conditions (the CDC). A reviewer checks that the code matches the request. If the code and the request don't line up, the claim can be denied.
Clinical Rationale and Supporting Documentation
The clinical rationale is the heart of the letter. Your doctor explains why the service is needed now, what other options were tried, and what is expected to happen if the service is approved or denied.
Attach the records that back up each claim. Common examples include:
- Office visit notes
- Test results and imaging reports
- Medication history showing prior treatments that did not work
- Specialist referrals
Tie every statement in the letter to a page in your records. That makes it easy for a reviewer to confirm what you wrote.
Step-by-Step: Writing the Letter
A letter of medical necessity works best when your doctor writes it in a fixed order that mirrors how a Medicare reviewer reads it. The steps below describe that order and explain what each part has to do.
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Open with identification. State the patient's full legal name, date of birth, and Medicare Beneficiary Identifier or plan member ID exactly as they appear on the card. A mismatch between the letter and the claim is one of the most common reasons for delay, so check each character.
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State the diagnosis with its ICD-10-CM code. Name the condition in plain clinical language and give the code. The code should describe the condition the service treats. If the request is for a lumbar MRI, the diagnosis should be the lumbar condition that justifies imaging, not a general symptom code.
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Describe the requested service precisely. Name the test, treatment, or item; the quantity, frequency, and duration; and, where relevant, the setting in which it will be delivered. A request for "physical therapy" is weaker than "twelve sessions of physical therapy over six weeks, two sessions per week."
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Write the clinical rationale in order of cause and effect. Start with the findings that establish the problem, such as examination results or imaging, then explain what the requested service will determine or treat. Two to four sentences is usually enough. Each sentence should name a finding or a decision, not a general claim.
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List prior treatments with dates and outcomes. Reviewers look for evidence that less intensive options were tried. Name each treatment, its duration, and the result: for example, "NSAIDs for eight weeks without sustained relief" is more persuasive than "conservative treatment was attempted."
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Tie statements to attached records. Refer to each record by type and date, such as "office note dated 04/02/2026." This lets the reviewer confirm each claim without searching.
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Close with the signature block. The doctor signs, dates, and includes the practice name, address, and National Provider Identifier. An unsigned or undated letter can be returned without review.
Keep the language plain. Reviewers read many of these letters, and a short, specific letter is easier to approve than a long one that buries the request. Avoid promotional phrases such as "essential" or "critical" unless the record supports the claim, because they add nothing a reviewer can verify.
The steps below run in the order a Medicare reviewer reads the letter, so each part can be checked against the records. For more practical guidance on preventing prior authorization problems before you submit, see our guide.
| Step | What to include | Note |
|---|---|---|
| 1. Identification | Full legal name, date of birth, Medicare or plan ID | Must match the card exactly |
| 2. Diagnosis | Condition in plain clinical language with ICD-10-CM code | Code should match the condition the service treats |
| 3. Requested service | Test or treatment, quantity, frequency, duration | Specific wording is stronger than general terms |
| 4. Clinical rationale | Findings that establish the problem, then the decision they support | Two to four sentences is usually enough |
| 5. Prior treatments | Each treatment, its duration and result | Shows less intensive options were tried |
| 6. Record references | Record type and date, such as office note dated 04/02/2026 | Lets the reviewer confirm each claim |
| 7. Signature block | Signature, date, practice name, address, NPI | Unsigned or undated letters can be returned |
Letter of Medical Necessity Example for a Medicare Request
Here is a simplified example of how the core of a letter might read:
"Mr. Jones (DOB 03/14/1952, Member ID on file) has a confirmed diagnosis of chronic lumbar radiculopathy (ICD-10 M54.16). Conservative treatment including physical therapy and a twelve-week course of prescribed medication has not relieved his symptoms. A lumbar MRI is requested to guide the next treatment decision. Records of prior treatment are attached."
Notice that each sentence does one job. It names the person, the diagnosis, the request and the reason. Your own letter should follow the same pattern, using your records.
Letter of Medical Necessity Template PDF: What to Look for
Many people search for a template PDF. A template can help you organize your thoughts, but look for one that includes:
- Clear fields for patient details and the ICD-10 code
- Space to describe the requested service
- A section for the clinical rationale
- A place for the doctor's signature and date
Avoid templates that promise approval. No form guarantees that a plan will accept a request. Your doctor's notes and records do the real work.
How to Ask Your Doctor for a Letter of Medical Necessity
Ask early. Writing and reviewing a letter takes time, and your doctor may need your records first. When you make the request, bring:
- The name of the service or item you need
- The plan name and any denial notice you received
- Copies of relevant test results and prior treatment notes
Be clear about the deadline. Ask your doctor's office how long they usually need to prepare the letter.
Handling a Denial and Filing an Appeal
A denial is not the final word, but the appeal has to be built around the specific reason the plan gave. A Medicare Advantage plan that denies coverage should issue a written notice explaining the decision. Read it first. If you want to know what steps to take after a denial, see what to do next after a Medicare Advantage claim is denied.
The Medicare standard for "reasonable and necessary" is the question the reviewer is answering. The reviewer applies the coverage standard Medicare uses for "reasonable and necessary" services; check Medicare.gov for the current rules. A revised letter should therefore speak to that test directly: state the diagnosis, the clinical findings that support it, the treatments already tried and their results, and why the requested service is the next appropriate step. Vague statements such as "my patient needs this" do not answer the reviewer's question.
Medicare Advantage appeals run through a series of levels. Learn more about your balance billing protections when a provider charges more than expected. The first step is usually a reconsideration by the plan, and further levels of review may follow if the denial is upheld. Confirm the process on the denial notice or at Medicare.gov. Each level has its own filing deadline, so check the denial notice and calendar it as soon as the notice arrives (Appeals in Medicare health plans).
A practical appeal packet usually contains four items:
- A copy of the denial notice
- An updated letter of medical necessity from your doctor that addresses the specific denial reason
- New or previously missing records, such as a test result or a note documenting a failed treatment
- A short cover statement that identifies the claim and the reason you disagree
Ask your doctor to respond point by point to the plan's stated reason. A letter that repeats the original request with no new clinical detail rarely changes the outcome. A letter that answers the exact objection, with the record cited, gives the reviewer a reason to decide differently.
Watch out: if your doctor has not seen the denial notice, the updated letter may miss the reason entirely, so send the notice to the office along with your records.
Your Next Step: Confirm Your Coverage Before You Submit
A well-written letter is only one part of getting coverage. Before you submit a request, confirm that the service is covered under your specific plan and that your providers are in network.
An independent advisor can help you check your coverage options. Get Free Quote to start the conversation at no cost and with no obligation.
Frequently Asked Questions
Does Medicare require a letter of medical necessity?
Not for every service. Medicare requires that items and services be reasonable and necessary, and a letter of medical necessity is a common way for a prescribing provider to document that. Some items, such as durable medical equipment, often need documentation to support a coverage determination or prior authorization, while routine services usually do not. Check the specific requirements for the item you need, and confirm with your plan or the official Medicare.gov resources before submitting.
Who can write a letter of medical necessity for Medicare?
The letter is usually written by the treating or prescribing physician or another qualified healthcare provider involved in your care. The provider knows your diagnosis, treatment history, and clinical needs, which the letter must explain. Patients and advisors can help organize records and gather documents, but the clinical justification should come from the provider. Your plan may also list specific requirements about who can sign the request.
Can I write my own letter of medical necessity?
You can prepare a draft or organize the information, but the letter should be signed and clinically supported by your provider. Medicare reviewers look for a clinical rationale tied to your diagnosis and records, which a patient typically cannot supply on their own. Ask your doctor to review, edit, and sign the final version so it reflects accurate medical judgment and the documentation in your chart.
What information should a letter of medical necessity include?
A complete letter usually includes the patient's name, date of birth, and Medicare or plan identifier, the diagnosis with the correct ICD-10 code, a description of the recommended item or service, and the clinical rationale explaining why it is reasonable and necessary. It should also list supporting documentation such as office notes, test results, and treatment history, and be dated and signed by the provider with their credentials and contact information.
