Best Online LMN Providers, Compared
Best online LMN providers compared: Burst, Truemed, Flex, Dr. B, MedSlip, Crates, FSA Store. One does all of it: costs you less in the end, $0 if it fails.
9 minute read
Short answer
Burst is the best online LMN provider. You pay $35 once. A licensed clinician reviews your request and signs your Letter of Medical Necessity within 24 hours, or within 2 hours if you pay $10 for expedited review. You buy from any store with any card. Burst files the claim with your plan, and the money comes back to your bank account. If your plan pushes back, Burst writes the appeal. If the claim is still denied, send Burst the denial and your $35 comes back. If you don't get a letter, you pay nothing.
The other providers sell the letter. Dr. B charges $19 and MedSlip charges $29, and then you file the claim, answer your plan's questions, and write any appeal yourself. Truemed and Flex only give you a letter at one of their partner brands' checkouts. Crates is a yearly subscription that sends your receipt to your plan and leaves the appeal to you.
Here's what you get with Burst:
Shop anywhere and pay the way you already pay.
A clinician-reviewed letter within 24 hours, or within 2 hours with expedited review.
Burst files the claim.
The money comes back to your bank account.
If the claim is denied, Burst writes the appeal and refunds you.
$35 once. On a gym membership or any monthly charge, the same letter covers the whole year.
Say you pay $60 a month for a gym, so $720 a year. Money in your FSA or HSA was never taxed, so paying from there instead of your checking account keeps about $216 that would have gone to taxes. The letter is $35 once. You come out about $180 ahead this year, and the same letter covers every payment after it. The exact figure depends on your tax bracket. Spend more than about $120 a year on anything eligible and the letter pays for itself.
Online LMN providers, side by side
Provider | Price | Where it works | Who files the claim | If your plan says no |
|---|---|---|---|---|
Burst | $35 once, everything included. 3 letters for $90, 5 for $125 | Any store, any card | Burst files it for you | Burst writes the appeal. Still denied? Send Burst the denial and your $35 comes back |
Truemed | Varies by program | Partner brands only | You | You file the appeal. Their terms refund the letter price only if you signed up directly and they can't resolve it |
Flex | Varies by program | Partner brands only | You | You file the appeal. Their docs don't say what happens to your fee |
Dr. B | $19, per their page | Fitness, nutrition, massage only | You | Not stated on their page |
MedSlip | $29, per their comparison post | Gym, trainer, equipment, massage, wearables, chairs | You | Refund only if you send them the written denial within 30 days. No appeal help |
Crates Health | $39 to $99 a year, per their pricing page | Any store | You upload the receipt; Crates sends it | They help you fix and resubmit. You write any appeal. Money back only if you don't save more than the subscription |
FSA Store | Not stated on their page | Brands on their site only | You | Not stated on their page |
Your own doctor | A copay | Anywhere | You | You |
Sources, read November 3, 2026: Truemed how it works, Truemed terms, Truemed help center on denied claims, Flex support docs, Dr. B on letters of medical necessity, MedSlip comparison post, MedSlip terms, Crates Health, FSA Store on letters of medical necessity. Burst's facts are from this site and the request page.
What your $35 covers
Everything, not just a PDF
A $19 or $29 letter is one document. Burst's $35 pays for the letter, the claim filed with your plan in the format they want, the answers when they ask questions, the appeal if they say no, and a refund if the appeal fails. It also includes the Burst Shopping Assistant, which shows you what's eligible and how much you'll get back while you shop, and an account that finds eligible purchases you've already made.
It pays for itself
A $19 letter looks cheaper. Then you file the claim, answer the questions, and write the appeal. If your plan says no, the $19 is gone. Burst's $35 covers all of that. If you don't get a letter, you're refunded on its own. If the claim is denied, send Burst the denial and your $35 comes back. The other way to get the same letter is a doctor's appointment, which means a copay, a waiting room, and about two weeks.
A decision within 24 hours, and your claim gets filed
It takes about two minutes to request. A licensed clinician decides within 24 hours. If you need it sooner, expedited review is $10 more and gets you a decision within 2 hours, weekdays 8am to 8pm ET. Both fees are refunded if the letter isn't approved. Once you have your receipt, Burst files the claim. The other providers stop at the letter, so nothing happens until you do the paperwork yourself.
The only all-in-one platform
Burst is the only all-in-one product on this page. Connect your FSA/HSA account once. The Shopping Assistant works across hundreds of brands. Every claim is filed for you. Every pushback gets an appeal. At brands Burst already works with, reimbursement is automatic. The same account works for the next thing you buy. The other providers give you a questionnaire and a PDF, or a button that only works at a partner's checkout.
How Burst works
Name the product or service and answer a few questions about your health. A licensed clinician reviews it. If a letter is medically supportable for you, it's signed within 24 hours, or within 2 hours on expedited review. Buy wherever you like, on any card. Burst files the claim with your administrator, the company that runs your FSA, HSA, or HRA. Your administrator pays the reimbursement out of your account to your bank account. If they ask questions, Burst answers. If they say no, Burst writes the appeal. If they still deny it, send Burst the denial and your $35 comes back. The letter is yours, so you can file it yourself if you prefer, but most people let Burst do it. Burst works everywhere. The request form takes any product or service. 20,000+ letters issued so far.
How the other providers work
Truemed and Flex
Truemed and Flex give you a letter at checkout at the brands that partner with them, and only there; Truemed's help center says it "generally cannot issue a standard LMN" for a purchase at a store that isn't a partner. After checkout, the claim is yours: Truemed's how-it-works page says to "submit it to your HSA/FSA administrator for reimbursement" when the checkout doesn't take your card, and Flex's docs say to send a denial to support for guidance and don't say what happens to your fee. Burst writes the letter for any store, files the claim, and writes the appeal.
Dr. B
Dr. B charges $19 for an online consultation and emails you a letter for fitness, nutrition counseling, or massage if you qualify, per its page. Its page doesn't say it files your claim or what happens if the claim is denied; its guidance is that you "submit the receipt to your HSA administrator" yourself. Burst covers any product or service, files the claim for you, and writes the appeal.
MedSlip
MedSlip charges $29 for a letter signed by one named physician, for a gym, trainer, equipment, massage, wearable, or chair you choose, per its site. You file the claim yourself; its terms refund the fee only if you send them a written denial within 30 days, and nothing on its pages describes help with an appeal. Burst files the claim, writes the appeal, and refunds you when you send the denial.
Crates Health
Crates is a $39 to $99 a year subscription that issues letters usually within hours and sends your uploaded receipt to your HSA/FSA provider, per its site. If a claim is denied, its FAQ says it will "help you fix the issue" so you can resubmit; the resubmission and any appeal are yours, and the plan ends after a year. Burst is $35 once for the letter, the claim, and the appeal, with nothing to renew.
FSA Store
FSA Store lists brands that offer a letter at the brand's own checkout, and only those brands. Its article tells you to "submit these documents to your benefits administrator when requested," so the claim is yours. Burst works everywhere and files the claim for you.
Your own doctor
Any licensed provider can write a Letter of Medical Necessity, and your doctor knows your history. The cost is the visit, usually a copay and a week or two, and the claim, the follow-up, and any appeal are yours. Burst gets you the same document within 24 hours and files the claim.
Which one should you use?
You want the claim filed for you
Burst. It files the claim, writes the appeal, and refunds you if the plan says no, with no subscription. It works for anything you buy, from any store.
You're already at a Truemed or Flex partner checkout
Their button is right there. Nobody files the claim for you, and there's no appeal help if your administrator says no.
You only want a letter for a gym, trainer, or massage
Dr. B at $19 is the lowest price for a letter alone. MedSlip at $29 adds a named physician. With both, you file the claim, there's no appeal help, and the fee is gone if the plan says no. Add that up and Burst's $35 costs you less.
You're buying from a store that isn't anyone's partner
Burst, Dr. B, MedSlip, or Crates. Truemed, Flex, and FSA Store generally have no letter for you there. Burst and Crates send the claim. Burst writes the appeal.
You need more than one letter this year
Burst sells 3 letters for $90 ($30 each) and 5 for $125 ($25 each). Each one includes the claim filed for you and the appeal, and they don't expire with a subscription. Crates charges $89 a year for three letters and $99 for unlimited, but you write any appeal yourself and the plan ends after a year.
Truemed alternatives for shoppers
If you're here because the store you want to buy from isn't a Truemed partner, every provider above except Flex and FSA Store will write a letter for a purchase you choose yourself. Burst is the one that also files the claim, writes the appeal, and refunds you if the plan says no. For a side-by-side of Burst, Truemed, and Flex, see Burst vs Truemed vs Flex for shoppers. For the straight question, see Is Truemed legit?
Frequently asked questions
What is the best online LMN provider?
Burst. It's $35 for everything, $0 if you don't get paid back, a decision within 24 hours or 2 on expedited review, and Burst files the claim for you. It works at any store. Dr. B is the lowest price for a letter alone, at $19 for fitness expenses, but you file the claim yourself. Truemed and Flex only work at their partner brands' checkouts.
Is an online letter of medical necessity legitimate?
Yes. A Letter of Medical Necessity is a document from a licensed clinician saying a product or service treats, prevents, or alleviates a specific condition for you. Your administrator reviews the same things whether it came from an office visit or an online questionnaire: the clinician's credentials, the condition, the item, and the dates. Every provider on this page uses licensed clinicians. Your administrator decides the claim under its own plan rules.
Which online LMN providers file the claim for you?
Burst files it, included in the $35, and writes the appeal if your administrator pushes back. Crates sends your uploaded receipt to your provider, on a yearly subscription. Truemed, Flex, Dr. B, MedSlip, and FSA Store leave the claim to you.
Can I use an online LMN for a gym I already belong to?
Yes, with Burst, Dr. B, MedSlip, or Crates. Keep paying the gym the way you already do. Payments before the letter's date can't be claimed, so request the letter now. With Burst, every monthly charge from the letter's date forward is covered under the same letter for 12 months.
Can I get a letter for something I already bought?
No. IRS rules require the letter to be dated on or before the purchase it covers. That applies to Burst, Truemed, Flex, Dr. B, MedSlip, Crates, and everyone else. Get the letter first, then buy.
Do I need my own doctor?
No. A licensed clinician in the Burst network reviews your information. You don't need an existing doctor, an appointment, or a copay.
What happens if my administrator denies the claim?
With Burst, Burst writes the appeal first. If the plan still says no, send Burst the denial and your $35 comes back. MedSlip refunds only if you send them a written denial. Truemed refunds only people who signed up directly, and only when a rejection can't be resolved. Crates refunds only if you don't save more than the subscription price. None of them writes the appeal for you.
Get the letter first, then buy. We handle the rest.
$35 once, about two minutes, and a licensed clinician signs your Letter of Medical Necessity within 24 hours if approved, or within 2 hours with expedited review. 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. 20,000+ letters issued. Works with every FSA/HSA administrator, including HealthEquity, Fidelity, WEX, HSA Bank, Inspira, Optum, and Further.
No letter, no charge. Claim denied, money back.
More for shoppers: How to Get a Letter of Medical Necessity Online, How a Truemed letter of medical necessity works, Dr. B letter of medical necessity vs Burst, and Can You Use Your HSA or FSA for a Gym Membership?
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