What Is a Letter of Medical Necessity (LMN) — And How It Unlocks Your HSA
- Saving Wiser
- Apr 23
- 4 min read
Updated: 5 days ago
There’s a powerful document many HSA users haven’t discovered yet — and it can help you use your HSA more intentionally across your health, fitness, and everyday wellness needs.
It’s called a Letter of Medical Necessity (LMN).
It’s not complicated, but it does change how certain expenses are evaluated. Once you understand how it works, you start looking at health purchases differently — especially those that fall into the “gray area.”
This guide covers what an LMN is, who can write one, how to get one, and where it actually makes a difference.
What Is a Letter of Medical Necessity?
A Letter of Medical Necessity (LMN) is documentation from a licensed healthcare provider that explains:
Your medical condition
Why a specific product or service is needed
How it treats or manages that condition
Under IRS Section 213(d), eligible expenses must be for the:
“diagnosis, cure, mitigation, treatment, or prevention of disease.”
An LMN helps connect a purchase to that definition — particularly when the item could otherwise be considered general wellness.
Example:
Without LMN → Iron Supplement = general wellness (not eligible)
With LMN tied to a documented deficiency → potentially HSA eligible
Same product. Different classification.
Sources:
IRS Publication 502
IRS Code §213(d)
Why LMNs Matter Today
LMNs have been part of healthcare for years — and they’ve consistently helped people access the care and tools they need.
Traditionally, they’ve been used for things like:
CPAP equipment
Orthotics
Home modifications
Medical devices not covered by insurance
What’s changed is accessibility. Today, it’s easier to connect everyday health purchases to real, documented needs — when appropriate.
The IRS rules haven’t changed. What’s improved is your ability to use those rules more intentionally to support your health and make the most of your HSA.
What an LMN Can Cover (With Limits)
An LMN may support expenses that are not automatically eligible, but only if they are clearly tied to a medical condition.
Common categories where LMNs are used:
Supplements (for diagnosed deficiencies)
Certain medical-grade devices
Sleep-related tools (if tied to a condition)
Some fitness or therapy-related expenses
Important clarification
An LMN does not automatically make something eligible.
Final approval depends on:
Your HSA administrator
Whether the expense meets IRS criteria
Quality of documentation
When in doubt, verify before purchasing.
Who Can Write an LMN
An LMN must be issued by a licensed provider authorized to diagnose and treat.
Typically accepted:
MD / DO
Nurse Practitioner (NP)
Physician Assistant (PA)
Licensed mental health professionals
Registered dietitians (for nutrition-related conditions)
Chiropractors (for musculoskeletal issues)
Not accepted:
Unlicensed Health coaches, Personal trainers or wellness providers
Always ensure the provider is licensed in your state.
Source:
IRS Publication 502 (qualified medical expenses must be for diagnosis/treatment of disease and typically require services from legally authorized healthcare providers; does not provide a fixed provider list)
Two Ways to Get an LMN
1. Through Your Doctor: This is the most traditional route. Best when:
You have an existing diagnosis
Your doctor knows your history
The item is clearly tied to treatment
How to approach it:
“I’m managing [condition], and I believe [product] would help. Would you be able to provide a Letter of Medical Necessity?”
Simple, direct, and usually quick.
2. Through a Platform (e.g., Truemed): Some platforms connect you with a clinician who reviews your health information and may issue an LMN if appropriate.
Typical flow:
Complete intake
Clinician review
LMN issued if criteria are met
This can be faster, but still relies on legitimate medical condition and approval.
What a Proper LMN Should Include
A strong LMN should clearly document:
Patient Info
Name
Date of birth
Provider Info
Name and credentials
License number
Signature
Medical Justification
Diagnosed condition
Explanation of need
How the item helps
Product Scope
Specific product or category
Duration (often ~12 months)
Missing details = higher chance of denial.
Consult your HSA Administrator for their specific policies and forms.
How Long an LMN Lasts
Most LMNs are valid for 12 months.
During that time:
Multiple purchases may be covered
Renewal is typically required annually
An LMN typically applies to a type of product tied to a condition — not necessarily a single transaction.
That means:
You may be able to use the same LMN across multiple purchases for the valid period.
Potentially from different retailers if the retailer is not specified in the LMN.
How to Use an LMN for Purchases
Get your LMN first: Make sure it clearly connects your condition to the product or category.
Make your purchase:
Use your HSA card (if your administrator allows), or
Pay with a personal card and plan to reimburse yourself
Choose your reimbursement timing:
Reimburse yourself right away, or
Keep your receipt + LMN on file and reimburse later to allow your HSA investments to continue growing
Maintain documentation for a minimum of 3 years, preferably 7 years, in case of an audit. Seek advice from a tax professional for further clarification based on your tax situation.
Sources:
IRS Publication 969
IRS Notice 2004-50
Common Mistakes to Avoid
Here are some common mistakes:
Not verifying with your HSA administrator
Missing receipt or incomplete documentation
Using an unqualified provider
Assuming approval is automatic
The Bigger Picture
An LMN is not a loophole.
It’s a documentation tool recognized by the IRS — but it only works when:
The condition is legitimate
The treatment is appropriate
The documentation is accurate
Used correctly, it can expand how you use your HSA — especially for expenses that sit between “medical” and “wellness.”
It's Your Turn
Think about the last three to six months of health purchases you made out of pocket.
Supplements. A fitness tracker. Exercise equipment. Shoes. Pillows.
How many of those could have been covered with pre-tax HSA dollars — with a Letter of Medical Necessity?
For most people the answer is more than they expect.
Talk to your doctor or visit Truemed to see what you qualify for.
Real savings on purchases you are already making. That is saving wiser.
Thank you for reading, The Save Wiser Team
Disclaimer: This content is for informational purposes only and not medical, tax, or financial advice. HSA eligibility depends on IRS rules and your plan administrator. Always consult a qualified professional.
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