Sample Letter of Medical Necessity for HSA/FSA (With Template)

A Letter of Medical Necessity (LMN) is a formal document from a licensed healthcare provider that explains why a patient needs a specific product, service, or treatment for a diagnosed medical condition. LMNs are used in two places: to show that a dual-purpose purchase, like a gym membership, an air purifier, or supplements, is HSA or FSA eligible for qualifying customers, and to support an insurance claim when you're seeking coverage for a treatment or medical equipment.

Below is a sample medical necessity letter, the key components every LMN should include, and how to request one from your physician. One important note up front: you can't write your own LMN. It has to come from a licensed healthcare provider who has evaluated your medical condition. This template shows what providers typically include, so you know what to ask for.

When do you need a Letter of Medical Necessity?

You don't need an LMN for everything you buy with an HSA or FSA. Prescriptions, doctor visits, over-the-counter medicines, first aid supplies, and similar items are eligible on their own. You typically need an LMN to pay with HSA or FSA benefits for products and services that have both medical and everyday uses, such as:

• A gym membership or personal training for managing obesity, hypertension, or diabetes
• Massage therapy for an injury or chronic pain
• Vitamins and supplements for a diagnosed deficiency
• Air purifiers for asthma or allergies
• Specialty mattresses or pillows for a back condition
• Weight-loss programs for a diagnosed medical condition

IRS rules don't treat these as automatically covered, because they can also be used for general well-being. An LMN is the medical justification that connects the item to managing a specific condition and supporting the patient's health. See our FSA eligible items list to check which items need one.

LMNs for HSA/FSA purchases vs. insurance claims

The same kind of letter serves two different processes:

• HSA and FSA benefits. The letter demonstrates that a dual-purpose product or service addresses a specific medical condition, rather than general well-being, which is what makes the expense eligible for reimbursement. You keep the document with your records and include it with a reimbursement request if your plan administrator asks for it.
• Insurance claims. When you're seeking coverage for a service, medication, or durable medical equipment your plan doesn't automatically cover, like a CPAP machine, a wheelchair, or a specialty device, your physician may submit an LMN on your behalf with the claim or prior authorization request, which is especially common for out-of-network care. Insurance LMNs often include more detail, such as clinical notes, test results, treatments already tried, and supporting research that justify the request.

Some insurers and benefits administrators provide their own LMN form, so ask whether one is required before your physician writes a letter from scratch. Using the right form can speed up reimbursement and claim decisions.

Key components: diagnosis, medical history, and recommended treatment

There's no official IRS form, but plan administrators and insurers typically look for the same details in the document. A complete Letter of Medical Necessity includes:

1. Patient information: patient name, date of birth, and the date of the letter.
2. Diagnosis: the patient's medical condition, often with the diagnosis code.
3. Treatment description: a description of the specific product, service, device, or equipment, as part of the patient's treatment plan.
4. Clinical rationale: a detailed explanation of how the treatment addresses the condition and supports the patient's health, based on the patient's medical history and clinical notes. This is the part that justifies the expense.
5. Duration: how long the treatment is needed, such as 12 months.
6. Provider details: the healthcare provider's name, credentials, license number, contact information, and signature.
7. Supporting research (optional): for insurance requests, providers sometimes reference clinical guidelines or research that support the recommended treatment.

Sample medical necessity letter for a gym membership

Here's an example of how a provider might write an LMN for a gym membership. The bracketed details are filled in by the provider based on their evaluation of the patient.

[Date]

To: [Plan administrator, HSA/FSA provider, or insurance company]

Re: Letter of Medical Necessity for [Patient name], DOB [Date of birth]

I am writing to confirm that my patient, [Patient name], has been diagnosed with [medical condition, e.g., stage 1 hypertension] ([diagnosis code]). Based on my evaluation and the patient's medical history, I recommend [specific treatment, e.g., a supervised exercise program at a fitness facility, three times per week] as part of the patient's treatment plan.

This treatment is medically necessary because [clinical rationale, e.g., regular aerobic exercise is a first-line intervention to lower blood pressure and reduce the need for additional medication]. The recommended duration of treatment is [e.g., 12 months], after which I will reassess the patient's condition.

This recommendation is to treat the patient's diagnosed condition and is not for general health. Please contact me at [phone or email] with any questions.

Sincerely,

[Provider name, credentials], [License number]

[Practice name and address]

[Signature]

This sample document is for illustration only. Your provider decides whether a treatment is medically necessary for you and writes the letter based on their own clinical notes.

How to request a Letter of Medical Necessity from your doctor

The process is usually simple:

1. Ask your healthcare provider. Your physician, nurse practitioner, or another licensed provider who treats your condition can write one. Bring details on the product, service, device, or equipment you need, and any LMN form your plan requires. It's essential that the physician who writes it is the one managing your condition. Be ready to describe your symptoms and how the condition affects your daily life.
2. Send a short written request. Many offices accept requests through a patient portal. You can use a message like the one below.
3. Use a telehealth consultation instead. Many merchants in the Flex Marketplace offer a short online consultation at checkout. A licensed provider reviews your health information, and if you qualify, you receive your LMN by email and can pay with your HSA or FSA card right away.
4. Get it before you buy. Make sure your LMN is dated before your purchase, so any reimbursement request for the expense is supported from the start.
5. Keep the document with your records. Store your LMN with your receipts in case your plan administrator asks for it when you submit claims for reimbursement of eligible expenses.

Sample request to your doctor:

Hi Dr. [Name], I'm requesting a Letter of Medical Necessity for [product or service] as part of my treatment plan for [condition]. My HSA/FSA benefits administrator needs the letter to include my diagnosis, the recommended treatment, how it addresses my condition, and how long I'll need it. If you agree it's medically necessary, could you prepare one? Thank you, [Your name], [Date of birth].

Learn more in our guide to what a Letter of Medical Necessity is and how Flex handles telehealth LMNs for HSA/FSA purchases.

Common mistakes to avoid

• Writing it yourself. An LMN must come from a licensed provider who evaluated you. A self-written letter isn't valid.
• Leaving out the diagnosis. "Recommended for general wellness" won't support eligibility or insurance coverage. The letter needs a specific medical condition.
• Being too vague. Name the specific treatment, how often, and for how long. The clinical rationale should be a detailed explanation, not a single sentence.
• Letting it expire. Many plan administrators treat an LMN as valid for up to 12 months. Check your plan's guidelines and get a new letter when yours runs out.
• Buying first. It's essential to get the LMN before the purchase, not after, or your plan's benefits may not apply.