Hi, I'm Anthony, one of the co-founders at Burst. We started Burst because the IRS quietly built a system that lets you cover a wide range of health-adjacent purchases with pre-tax FSA and HSA dollars, and almost nobody knows how to use it. The piece that unlocks most of the value is one document: the Letter of Medical Necessity.

Short answer. An LMN is a brief note from a licensed clinician that says a specific product or service is part of how you're managing a specific health situation. With it, eligible-on-paper expenses become reimbursable. Without it, your plan administrator denies the claim. The rules come from the IRS (Pub 502 and Notices 2006-69 and 2007-2), and they apply uniformly: every LMN provider, including Burst, follows the same federal framework. Below is what you need to know about when an LMN is required, what makes one work versus get denied, and how reimbursement actually happens.

When you need an LMN

Plenty of FSA/HSA purchases don't need any paperwork. Prescription medications, prenatal vitamins, breast pumps, and over-the-counter medications under the CARES Act expansion are all default-eligible. The IRS publishes a list and your plan administrator follows it.

Where the LMN comes in is for the much larger set of purchases that the IRS calls dual-purpose. A treadmill can be exercise equipment. It can also be cardiac rehabilitation. A mattress can be furniture. It can also be sleep apnea management. The default eligibility status of these items is no, but with an LMN naming the medical context, they reimburse.

What's eligible with an LMN

• Fitness equipment. Peloton, Tonal, Hydrow, NordicTrack, Mirror, treadmills, rowing machines, adjustable dumbbells, walking pads.

• Recovery and wellness tools. Theragun, Hyperice, red light therapy panels (Joovv, Mito), saunas (Sunlighten), cold plunges (Plunge), HigherDOSE PEMF mats.

• Sleep and mattresses. Eight Sleep, Saatva, Helix, Purple, Casper, Tempur-Pedic, Nectar, Sleep Number, Mattress Firm.

• Wearables. Whoop, Garmin, Apple Watch, Fitbit, Coros, Amazfit, Wahoo. (Oura is on a separate IRS classification path — see our Oura guide.)

• Supplements. AG1, Ritual, Thorne, Momentous, magnesium, fish oil, collagen, super greens — when tied to a documented health context.

• Air and water quality. AquaTru and Boroux water filters, Blueair and Medify air purifiers, humidifiers.

• Subscriptions and memberships. Gym memberships (Equinox, Life Time, Anytime Fitness), Peloton All-Access, Pilates, yoga, Pelvic floor PT.

What an LMN actually has to say

The thing that gets LMNs denied isn't the LMN itself. It's that the LMN is too vague. Plan administrators read these. They reject LMNs that say things like "recommended for general wellness" or "to improve fitness." What they approve are LMNs that:

• Name the specific health situation being managed (not a generic wellness goal).

• Connect the product or service to that situation (the why matters as much as the what).

• Are signed by a licensed clinician.

• Are dated. LMNs typically last 12 months. After that, recurring expenses (memberships, subscriptions) need a refreshed LMN.

Burst's clinicians review every request and write LMNs in the language plan administrators actually approve. If our clinician decides a situation doesn't fit, you get a full refund. The fee for the Burst LMN itself is FSA/HSA eligible, so you can pay for it with your card.

How the reimbursement flows

Pay for the eligible product with any card. Get the LMN. Submit your receipt and LMN to your plan administrator (Optum, HealthEquity, Fidelity, HSA Bank, PayFlex, Navia, WEX, FSAFEDS, BoA). The reimbursement lands in your bank account from your FSA or HSA balance.

Burst clinicians have approved LMNs across more than 28 product categories at this point. The most common path: someone has a known condition (chronic pain, sleep issues, weight management goals tied to a doctor's recommendation, anxiety, post-surgical recovery), they're already paying for a product that helps, and the LMN turns that out-of-pocket spend into pre-tax spend. Save 30% on health products by using FSA or HSA dollars instead of post-tax money.

What an LMN does not do

• It does not cover purchases made before the LMN request date. Per IRS guidelines, an LMN is forward-looking from the date it's issued.

• It does not make consumer products that are unrelated to medical use eligible. Branded apparel, gift cards, and lifestyle accessories stay out of scope.

• It does not bypass your plan administrator's review. Plan admins still validate the LMN. A weak LMN gets denied no matter who wrote it.

• It does not work indefinitely. LMNs typically last 12 months. Recurring expenses need refreshes.

FAQ

Is an LMN the same as a prescription?
No. A prescription authorizes a specific medication. An LMN documents that a non-prescription product or service is part of treating a medical situation. They're different documents.

Can my regular doctor write the LMN, or do I need a specialist?
Any licensed clinician can write one. Many people find that the easiest path is to use a service like Burst that has clinicians who specialize in writing LMNs that plan admins actually approve.

What if my employer doesn't have an FSA?
If you have an HSA through a high-deductible health plan (HDHP), the same LMN rules apply. HSAs are typically more flexible than FSAs because they roll over year to year and can be invested.

Can I use an LMN to reimburse a past purchase?
Per IRS guidelines, LMNs must be for purchases made on or after the LMN request date. So an LMN you request today won't cover something you bought last month. If you're planning to buy soon, get the LMN first.

Is the LMN fee itself FSA/HSA eligible?
Yes.

Stop paying out-of-pocket

If you're already paying for any of the products above and you've got a health situation that fits, an LMN turns that spend into pre-tax savings of around 30%. Get yours from Burst in under 5 minutes. If our clinician doesn't approve it, you get a full refund.

Request my LMN →

If you're not sure whether your situation fits, hit reply on any Burst email or write to support@getburst.com. We read every email ourselves.

Thanks,
Anthony
CEO and Co-Founder at Burst

For the underlying rules, see IRS Publication 502, IRS Notice 2006-69, and IRS Notice 2007-2.

Last updated: May 2026

This guide is not medical advice. Your eligibility depends on your specific situation and your plan administrator's interpretation of IRS rules. Burst's clinicians make eligibility decisions on a case-by-case basis.