Quick answer: A Letter of Medical Necessity (LMN) is a short letter from your physician explaining that your cranial prosthesis is needed because of a medical condition or treatment — not for cosmetic reasons. Some insurance plans require one alongside (or instead of) a prescription, and HSA/FSA administrators often accept an LMN as documentation. Your doctor writes it; a good provider gives your doctor a template so it takes minutes.
What an LMN typically includes
Your name and the date · your diagnosis or the medical cause of hair loss (for example, chemotherapy-induced alopecia, alopecia areata, lupus-related hair loss) · a statement that a cranial prosthesis is medically necessary as a result · optionally, the expected duration of the need · the physician's signature, credentials, and contact information. It does not need to be long — a few sentences on letterhead is typical.
LMN vs. prescription: which do you need?
It depends entirely on your plan. Some insurers accept a prescription alone; some want both; HSA/FSA administrators frequently ask for an LMN. The only reliable answer comes from one phone call: "For a cranial prosthesis claim, do you require a prescription, a Letter of Medical Necessity, or both?" Ask before your doctor's appointment so a single visit covers everything. How to ask your doctor →
How ANIOR Medical helps
Every prosthesis purchase includes our physician letter template — written in the format insurers expect, ready for your doctor to adapt, sign, and return. Your physician remains the author; we simply remove the blank-page problem.
Reviewed by the ANIOR Medical team · Updated July 2026. General information, not medical or benefits advice.