The Ultimate Guide to Letters of Medical Necessity (LMN)
Everything about Letters of Medical Necessity for HSA and FSA reimbursement: what they are, when you need one, what they must say, and how to get one online for $35.
5 minute read
A Letter of Medical Necessity (LMN) can be the key to unlocking additional savings through your Health Savings Account (HSA) or Flexible Spending Account (FSA). Whether it's for nutritional supplements, massage therapy, or special equipment, an LMN can help you prove that a purchase is medically necessary, and thus eligible for reimbursement with pre-tax funds. Below is everything you need to know about letters of medical necessity, when to secure one, and how to draft an effective template. If you already know you need one, here is how to get a Letter of Medical Necessity online for $35.
If you already know you want an LMN, you can request one in about two minutes and skip the rest of this guide.
1. What is a Letter of Medical Necessity?
An LMN is a written statement from a licensed healthcare provider (e.g., doctor, nurse practitioner, therapist) that explains:
What item or service is being recommended.
Why it's needed for the diagnosis, treatment, or prevention of a specific medical condition.
Although many items are automatically eligible under IRS guidelines, certain products and services fall into a gray area. An LMN helps bridge the gap by clarifying the medical purpose.
For official details on qualifying medical expenses, refer to:
2. When You Need One
You'll likely require an LMN if:
The Item Is Not Obviously Medical
For instance, a massage chair might be perceived as a luxury item unless a doctor confirms it's part of a prescribed treatment plan.IRS Guidance Isn't Clear
If an expense falls into a “maybe” category (like nutritional supplements or weight-loss programs) an LMN can validate the medical need.Your FSA/HSA Administrator Requests It
Some administrators ask for an LMN for certain claims to ensure compliance with IRS rules.
Pro Tip: if a product needs a letter, get the letter first, then buy. Burst gets you one online for $35, usually the same day, and files the reimbursement for you.
3. How to Get One
Obtaining an LMN is relatively straightforward, and now you have two great options:
Option 1: Traditional Route
Consult Your Healthcare Provider
Schedule an appointment or contact your provider explaining that you need a medical necessity statement for your FSA or HSA.Be Specific
Provide details of the item or service you want covered and explain how it relates to your condition or treatment plan.Obtain a Dated, Signed Letter
The LMN should be on official letterhead, signed, and dated by your provider. Keep both digital and physical copies for future claims or audits.
Option 2: Get one online with Burst
$35 once, about two minutes, and a licensed clinician signs your Letter of Medical Necessity, usually the same day if approved and always within 24 hours. Then buy from any store with any card, and Burst files the reimbursement claim for you, start to finish. If your administrator pushes back, we write the appeal.
15,000+ letters issued. Works with every FSA/HSA administrator.
No letter, no charge. Claim denied, money back.
About two minutes to request · usually the same day · we file the claim for you.
4. LMN Template/Example
Below is a sample LMN. Note that each provider may format or word it differently, but these elements are commonly required.
Questions people ask before they request
Will my HSA or FSA administrator accept it?
Yes. Administrators want a signed letter from a licensed clinician that names your condition and the item, and that is exactly what you get. Burst works with every FSA/HSA administrator, including HealthEquity, Fidelity, WEX, HSA Bank, Inspira, Optum and Further. If one pushes back, we write the appeal. If the claim is denied, you get your $35 back.
Do I need to see a doctor?
No. Answer a few questions online and a licensed clinician in the Burst network reviews them. No appointment, no copay, no waiting room.
What if I am not approved?
You pay nothing. No letter, no charge.
How fast is it?
About two minutes to request. Your letter usually arrives the same day, always within 24 hours.
Who files the reimbursement claim?
We do, start to finish. Send us the receipt and Burst files the claim with your administrator; the money comes back to your bank account.
I already bought it. Can I still get the letter?
Get the letter first, then buy. It covers what comes after it is issued, not what came before. If you have a recurring charge, it covers the next one onward.
What is the difference between an LMN and a prescription?
A prescription authorizes a specific medication. A Letter of Medical Necessity documents that a non-prescription product or service is part of treating a diagnosed condition, which is what lets you claim it from an FSA or HSA.
Who can write an LMN?
Any licensed clinician: an MD, DO, NP or PA, and in some states a licensed naturopath. Burst's letters are signed by US-licensed clinicians.
How long is an LMN valid?
Typically 12 months from the issue date. Recurring purchases such as a membership or a monthly supplement are covered for that period; after it ends you request a fresh letter.
Does the LMN have to be on letterhead?
Administrators expect formal documentation: the clinician's name, credentials and license, a signature and a date, the condition and the item. Burst's letters carry all of it.
In Summary
A Letter of Medical Necessity can make the difference between tax-free FSA/HSA reimbursement and out-of-pocket costs for borderline or uncertain healthcare expenses. By securing an LMN from your provider (or by getting one from Burst for $35, usually the same day) you'll ensure you never miss out on tax-free HSA savings.
With the right documentation in place, you can confidently expand your FSA/HSA eligible purchases and fully optimize your healthcare dollars.
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