How to Get a Letter of Medical Necessity for Your HSA

Short answer: A Letter of Medical Necessity (LMN) is a document from a licensed healthcare provider stating that a specific expense is medically necessary for treating or preventing a condition. You can get one from your doctor, a telehealth provider, or through a service like Hammock that includes unlimited LMNs.

What Is a Letter of Medical Necessity?

A Letter of Medical Necessity (LMN) — sometimes called a physician's statement or medical necessity letter — is a formal document that connects a specific expense to a medical need. It's the key that unlocks HSA and FSA spending for items and services that aren't on the IRS's default list of qualified medical expenses.

Without an LMN, expenses like gym memberships, supplements, massage therapy, and certain equipment are considered "general health" — not medical expenses. With an LMN, they become qualified medical expenses that you can pay for with pre-tax HSA or FSA dollars.

What an LMN Must Include

A valid LMN typically contains:

Patient information — Your name and date of birth

Provider information — The licensed provider's name, credentials, and contact info

Diagnosis or condition — The specific medical condition being treated or prevented

Recommended treatment — The expense being prescribed (e.g., "gym membership for cardiovascular rehabilitation")

Medical justification — Why this expense is necessary for treating the condition

Duration — How long the treatment is recommended (e.g., "12 months, renewable")

Provider signature and date

What Conditions Qualify?

More conditions qualify than most people think. Common conditions that support LMNs for wellness expenses include:

Obesity or overweight — BMI-based recommendations for exercise and nutrition
Cardiovascular risk — High blood pressure, high cholesterol, heart disease prevention
Musculoskeletal conditions — Back pain, joint problems, repetitive strain
Mental health — Anxiety, depression, stress-related conditions
Metabolic conditions — Pre-diabetes, insulin resistance, metabolic syndrome
Chronic pain — Conditions benefiting from massage, acupuncture, or exercise
Sleep disorders — Insomnia, sleep apnea, related issues
Autoimmune conditions — Conditions where exercise or supplements support treatment

Most adults have at least one condition that could support an LMN. You don't need to be seriously ill — preventive care and risk reduction count.

Option 1: Ask Your Doctor

The most traditional route. Schedule an appointment with your primary care physician and explain that you'd like a Letter of Medical Necessity for specific wellness expenses.

Pros:

Your doctor knows your medical history
They can tie the LMN to documented conditions
Insurance may cover the visit

Cons:

Many doctors are unfamiliar with LMNs
Appointments take time and may have copays
Some doctors are reluctant to write LMNs for "wellness" items
You'll need a separate LMN for each type of expense
Cost: $0–$50 (copay) plus time

Tips for asking your doctor:

Bring a template or example LMN
Explain what the letter is for (HSA qualification)
Frame it in medical terms ("I'd like exercise therapy for my diagnosed hypertension")
Be specific about what you want covered

Option 2: Telehealth LMN Services

Several telehealth companies specialize in LMN evaluations. You complete a health questionnaire, have a brief video or phone consultation, and receive your LMN.

Pros:

Quick and convenient (often same-day)
Providers are familiar with LMN process
No need to explain the concept

Cons:

Cost: $50–$200 per LMN
Quality varies significantly
Some HSA administrators may scrutinize telehealth LMNs
Need a new LMN (and payment) for each expense category

Option 3: Hammock (Unlimited LMNs Included)

Hammock includes unlimited Letters of Medical Necessity as part of its HSA membership. No per-letter fees, no separate appointments, no hassle.

Pros:

Unlimited LMNs — gym, supplements, massage, all covered
No per-letter cost (included in membership)
Built into the HSA platform — everything in one place
LMNs from licensed providers in Hammock's network
Covers all qualifying wellness categories

Cons:

Requires switching to (or adding) Hammock as your HSA provider
Annual fee (though tax savings typically exceed this)

What Expenses Can an LMN Cover?

With a valid LMN, these common expenses become HSA/FSA eligible:

Expense	Typical Cost	Annual Cost
Gym membership	$30–$150/month	$360–$1,800
Supplements (protein, vitamins)	$30–$100/month	$360–$1,200
Massage therapy	$60–$120/session	$720–$2,880 (biweekly)
Personal training	$50–$150/session	$2,600–$7,800 (weekly)
Meditation apps	$10–$15/month	$120–$180
Fitness equipment	$200–$2,000	One-time
Healthy meal programs	$200–$500/month	$2,400–$6,000

How to Use Your LMN

Once you have an LMN:

Keep it on file — Store a digital copy with your HSA records

Pay with your HSA debit card — Use it at the gym, supplement store, etc.

Match receipts to your LMN — Each receipt should correspond to an expense listed in your LMN

Be ready for documentation requests — Your HSA administrator may ask for your LMN during an audit

Renew annually — Most LMNs are valid for 12 months. Renew before they expire.

How Long Does an LMN Last?

Most LMNs are written for 12 months, though the duration is set by the provider. Some key points:

Check the expiration date — Don't assume it auto-renews
Renew before it expires — Expenses after expiration aren't covered
Keep historical LMNs — The IRS can audit up to 3 years back (6 years in some cases)
Update if conditions change — A new diagnosis might allow additional expenses

Frequently Asked Questions

Can a nurse practitioner or PA write an LMN?

Yes. LMNs can be written by any licensed healthcare provider authorized to diagnose and prescribe in their state — including MDs, DOs, NPs, PAs, and in some cases, licensed clinical social workers or psychologists.

Does my employer need to see my LMN?

No. Your LMN is between you, your healthcare provider, and your HSA administrator. Your employer has no right to see it.

What if my HSA administrator rejects an expense even with an LMN?

First, submit the LMN along with your receipt for review. If still rejected, ask for the specific reason. You can appeal the decision. In rare cases, you may need a more detailed LMN from your provider.

Can I get an LMN retroactively?

It's complicated. An LMN should ideally be dated before or at the time of the expense. Some providers will write LMNs covering a period that includes past expenses if the condition existed at that time, but this is a gray area. Best practice: get your LMN before you start spending.

Do I need a separate LMN for each expense?

It depends on the provider and the conditions. A single LMN can cover multiple expenses if they're all prescribed for the same condition. For example, one LMN might cover both gym membership and supplements for obesity management. However, having clear, specific LMNs for each category is safer from an audit perspective.

Is an LMN the same as a prescription?

Not exactly. A prescription is an order for a specific medication or treatment. An LMN is a statement of medical necessity that documents why an expense is needed. For HSA purposes, an LMN serves as the documentation that converts a non-qualified expense into a qualified one.

Ready to start using your HSA for wellness? Hammock includes unlimited Letters of Medical Necessity — so your gym, supplements, and massage are all tax-free.