A Letter of Medical Necessity (LMN) is a formal document that explains why a specific treatment, service, or device is essential for a patient’s health. Clinicians directly involved in the patient’s care such as physicians, therapists, and other licensed providers typically use the letter to justify insurance claims and obtain prior authorization for treatments.
This letter explains the clinical reasoning for the requested treatment and includes elements such as the patient’s diagnosis, treatment justification, and a formal request aligned with the overall care plan. This information strengthens the request and prevents delays during the coverage review.
How to Write a Letter of Medical Necessity
Each section of the LMN presents essential information about the patient’s condition and the reason for the recommended treatment. The following guide explains how to prepare a complete LMN for review by an insurance company or a medical benefit examiner.
Recipient’s Name and Address
Place the recipient’s contact details at the top of the letter. Include the name of the insurance company or medical reviewer, their department (if known), and the complete mailing address with street, city, state, and ZIP code. Add the phone number and email address, if available, to ensure the letter reaches the appropriate contact without delay.
Salutation
Begin with a formal salutation. If the reviewer’s name is available, use a personalized greeting such as “Dear Dr. Karen Mitchell.” If not, a general greeting like “To Whom It May Concern” is acceptable.
Subject Line
Use a clear subject line that identifies the patient and the purpose of the letter. Mention the requested treatment or equipment and the patient’s full name.
Opening Paragraph
Begin by stating your role as the patient’s attending physician and briefly explaining your professional relationship. Include the patient’s full name and date of birth for identification. Mention the medical diagnosis and ICD-10 code, and note how long the condition has been present or whether it has progressed. Then explain why standard treatments have not been effective or sufficient, especially in helping the patient manage daily activities independently and safely. This paragraph introduces the clinical context and establishes the need for the requested service, device, or treatment.
Body Paragraph (Medical Necessity and Treatment Justification)
Describe the treatment, service, or equipment being requested and explain how it relates to the patient’s diagnosis. Clarify that the recommendation is based on your clinical evaluation and medical judgment. Detail how this intervention will improve the patient’s ability to carry out daily tasks (activities of daily living or ADLs) and reduce the likelihood of future complications.
Request for Coverage
After outlining the medical rationale, formally request approval for the recommended treatment or equipment. Mention that the request is part of the patient’s ongoing care plan and that supporting documentation—such as clinical notes or diagnostic reports—is available upon request.
Closing Statement/Paragraph
Conclude the letter with a respectful closing. Invite the reviewer to contact you if additional information or clarification is needed. Avoid repeating medical details already mentioned. End with a courteous line thanking them for their time and consideration.
Signature Block
At the end of the letter, include a signature block with your full name, medical degree, and professional credentials. Add your official title, specialty, and the name of the medical facility. Leave space above or beside your typed name for a handwritten signature. This information confirms your involvement in the patient’s care and provides reviewers with a way to contact you for follow-up questions.
How to Complete the Letter as a Patient
As a patient or claimant, begin by customizing the template, which includes all required sections. Complete it with accurate personal and medical information. After filling out the form, bring it to your doctor for review. The doctor will verify the information, then sign and stamp the letter to validate it. Once signed, submit the letter along with any required documents to your insurance provider.
This letter template is available for customization in Microsoft Word and Google Docs formats. It can be completed digitally and printed for signing, as many insurers require a physical signature. A completed sample LMN letter is also included in the file as a reference when drafting your own. After submission, stay prepared to respond to any follow-up questions from reviewers and assist with the patient’s approval process.
