Home/ The Journal/ fsa hsa
fsa hsa
Letter of medical necessity for supplements: example, who can write one, and how to use your FSA
What is a Letter of Medical Necessity (LMN)? A plain-English guide with a sample letter, what it must include, how to get one, and how to use it with your FSA or HSA.
Short version: A letter of medical necessity for supplements is a signed note from a licensed provider, good for about 12 months. It ties a supplement to a condition you have been diagnosed with. The IRS only lets FSA or HSA money pay for a supplement when it is "recommended by a medical practitioner as treatment for a specific medical condition diagnosed by a physician" (IRS Publication 502).
- Who signs: a licensed provider who knows your case. Your plan decides which kinds it accepts.
- What it needs: your diagnosis, the product, why it helps, dates, and a signature.
- How long it lasts: about 12 months. Then you renew it.
- What it cannot do: turn a general wellness buy into a medical one.
Last updated October 2026.
Most supplements are not FSA or HSA eligible on their own. A fiber gummy, a vitamin D pill, or a magnesium powder is something you take to stay well. The tax rules call that personal spending.
A letter of medical necessity, or LMN, is the one door that can change that. It is also the door people most often walk through the wrong way. In March 2024 the IRS put out a warning about companies selling quick "doctor's notes" that do not hold up.
This guide shows what a real letter looks like, who can write one, and how to use it with your FSA. It is general information, not tax or medical advice.
What is a letter of medical necessity for supplements?
It is a short, signed statement from a licensed provider. It says three things. You have a specific diagnosed condition. A specific supplement is part of the plan for that condition. And the plan has a start date and an end date.
The letter matters because of how the IRS defines a medical expense. Publication 502 says medical care "must be primarily to alleviate or prevent a physical or mental disability or illness." It does not include costs that are "merely beneficial to general health." A supplement you take to feel good lands in the second group. A supplement your provider recommends for a diagnosed problem can land in the first.
An LMN is not a prescription
A prescription tells a pharmacy to hand you a drug. An LMN is paperwork for your health account. It explains why something that is not covered by default should count for you. You can need one even for an item you buy off the shelf.
Why do supplements need a letter when cold medicine does not?
Because the IRS sorts them into two different buckets.
Over-the-counter drugs are their own bucket. FSAs and HSAs can pay for them with no letter. The IRS confirms this in its FAQ on nutrition, wellness, and general health (question 13). Pain relievers, allergy pills, and antacids fall here.
Supplements are the other bucket. The same FAQ answers question 14 with "Yes, but only if the supplements are recommended by a medical practitioner as treatment for a specific medical condition diagnosed by a physician. Otherwise, the cost of nutritional supplements is not a medical expense."
So the letter is not a loophole. It is the proof that the "only if" part is true for you.
Food is a third bucket, with a stricter test. A special food counts only if it does not meet normal nutrition needs, it helps an illness, and a physician backs the need. Even then, you can only claim the amount above what regular food would cost (FAQ question 12).
Who can write a letter of medical necessity?
A licensed medical provider who is treating you. In most plans that means a doctor (MD or DO), a nurse practitioner, or a physician assistant. The form most plans use asks for the provider's license number and signature. Optum's version calls the signer your "licensed medical practitioner" and will not process a form without a signature.
Two limits are worth knowing.
- You cannot write your own. A self-written note carries no weight.
- Your plan sets the list. The IRS rule names a "medical practitioner" for the recommendation and a "physician" for the diagnosis. Each plan administrator decides which license types it accepts. Ask before you book a visit.
Can a chiropractor write one?
Sometimes. Publication 502 lists chiropractor fees as a medical expense, so chiropractic care itself can count. A letter for a supplement is a separate question. Some administrators accept a chiropractor's letter for care tied to the problem they are treating. Others want the diagnosis from a medical doctor, NP, or PA. Call the number on your FSA card and ask "Do you accept a letter of medical necessity from a chiropractor for this item?" before you pay.
A sample letter of medical necessity for a fiber supplement
Here is what a complete letter can look like. It is an illustration only. Your provider writes in their own words, and only if it fits your care.
[Clinic letterhead] · Date: [date]
To the plan administrator,
Patient: [Full name], date of birth [date]
Diagnosis: Chronic idiopathic constipation (ICD-10-CM K59.04)
I am this patient's treating provider. The patient has had chronic constipation for more than six months. Diet changes alone have not been enough.
As part of the care plan, I recommend a daily soluble fiber supplement, taken as labeled, to support regular bowel movements. In my clinical judgment this is medically necessary for this condition and is not for general health.
Start date: [date] · End date: [date, no more than 12 months later]
[Provider name, credentials] · License or NPI [number]
[Practice name, address, phone] · [Signature]
The code in the sample is real. K59.04 is the ICD-10-CM code for chronic idiopathic constipation in the National Library of Medicine's code list. Your provider picks the code that matches your chart, not the one in a sample.
What the form asks for, line by line
Many administrators give you their own form instead of a free-form letter. Optum's "Statement of Medical Necessity" is a common one. This is what it asks for, and why.
| Field on the form | Who fills it in | Why it matters |
|---|---|---|
| Your name, last 4 of SSN, employer | You | Matches the letter to your account |
| Diagnosis and code | Provider | Proves a specific condition, not general wellness |
| Recommended treatment | Provider | Names the exact product or service |
| How it will help the diagnosis | Provider | Links the product to the condition |
| Start and end date | Provider | End date cannot be more than 12 months out |
| Name, license number, practice, phone | Provider | Shows a licensed person reviewed your case |
| Signature and date | Provider | Unsigned forms are not processed |
The form also says plainly that sending it "does not guarantee that the associated expenses will be approved." The letter supports your claim. Your plan still decides.
How to use your letter with an FSA
A health FSA is an account your employer sets up. You put in pre-tax pay, then spend it on medical costs. For plans that start in 2026, you can put in up to $3,400 (IRS Publication 15-B).
- Ask your plan first. Confirm it accepts an LMN for supplements, and get its form if it has one.
- Get the letter before you buy. The start date should come before the purchase date.
- Buy and keep an itemized receipt. It needs the store, date, product name, and price.
- Send both to your plan administrator. That is the company that runs the account, not your employer or insurer.
- Keep copies. If the IRS ever asks, you need the letter and the receipt together.
Watch the calendar. FSAs are mostly "use it or lose it," per IRS Publication 969. Your plan may give you a grace period of up to 2.5 months, or let you carry up to $680 of unused 2026 money into the next plan year. It cannot offer both. For the fiber-specific claim walkthrough, see Can you use FSA or HSA for fiber supplements?
The IRS warning about instant doctor's notes
Some companies sell a "doctor's note" after a short online quiz. On March 6, 2024, the IRS said this does not work for general wellness spending (IR-2024-65).
In the IRS's words, notes "based merely on self-reported health information" cannot turn food, wellness, or exercise costs into medical ones. The expense still has to be tied to "a targeted diagnosis-specific activity or treatment."
The stakes are real. A plan that pays for non-medical costs can lose its tax status. Then every payment from it, even for real medical bills, can count as taxable income. That is why administrators look hard at these claims.
Telehealth is not the problem. A licensed clinician who actually reviews your history and diagnoses a condition can write a valid letter. The red flag is a letter that comes with your cart, for anyone who checks a box.
What a letter cannot do
- Make general health count. The IRS says exercise "only for the improvement of general health" does not qualify, "even if recommended by a doctor" (FAQ question 11).
- Cover the full price of food. Only the extra cost over normal food counts, and only with a physician-backed need (FAQ question 12).
- Reach back in time. A purchase made before the letter's start date is hard to claim.
- Guarantee a payout. Each claim is reviewed on its own.
Does a letter of medical necessity expire?
Yes. Optum's form says "A new Statement of Medical Necessity must be submitted each 12 months," and its end date cannot be more than 12 months out. WEX also says most letters are valid for one year, and some plans want renewal sooner. If you buy a supplement every month, set a reminder a few weeks before the end date.
Where a fiber gummy fits
Fiber is one of the more common supplements a provider may recommend for constipation. The evidence has a clear shape. A 2022 review of 16 randomized trials found fiber helped adults with chronic constipation. The gains showed up mostly at more than 10 grams a day, taken for at least 4 weeks. Psyllium and pectin had the strongest results.
That matters for a letter. A provider who recommends fiber may name a type and a daily amount. A gummy can be one part of that amount, alongside food.
Seya does not offer an FSA or HSA checkout today. If your provider recommends a fiber supplement for a diagnosed condition, you would pay first and then send your letter and receipt to your plan. Whether it is approved depends on your plan. Seya Full Fiber is a vegan gummy made with resistant tapioca fiber that supports regularity. It is a dietary supplement, not a medicine for any condition.
New to fiber? Start with how much fiber women need per day, then see which supplements are FSA or HSA eligible.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Frequently asked questions
What is a flexible spending account (FSA)?
An employer-run account you fund with pre-tax pay and spend on medical costs. For 2026 plans the limit is $3,400. Most unused money is lost at year end, unless your plan offers a short grace period or a small carryover.
Which medical expenses qualify under IRS Publication 502?
Costs to diagnose, treat, ease, or prevent a disease, or to affect a part or function of the body. Doctor visits, dental care, eye exams, and prescriptions qualify. Costs that are only good for general health do not. Supplements count only with a practitioner's recommendation for a diagnosed condition.
What medical and dental expenses are deductible?
The same ones Publication 502 lists as medical care. You can deduct only the part of the total that is more than 7.5% of your adjusted gross income, and only if you itemize. You cannot deduct a cost you already paid with FSA or HSA money.
Can a chiropractor write a letter of medical necessity?
It depends on your plan. Chiropractic care is a listed medical expense, but each administrator decides whose letters it accepts for supplements. Ask your plan before your visit.
Who can write a letter of medical necessity for supplements?
A licensed provider who is caring for you, usually a doctor, nurse practitioner, or physician assistant. They must diagnose a specific condition and explain how the supplement fits your care.
Does a letter of medical necessity guarantee reimbursement?
No. It supports your claim, but your plan reviews each one. Notes based only on an online quiz can be denied.
Sources
- IRS, Publication 502 (2025), Medical and Dental Expenses.
- IRS, Frequently asked questions about medical expenses related to nutrition, wellness, and general health.
- IRS, IR-2024-65, March 6, 2024.
- IRS, Publication 15-B (2026) and Rev. Proc. 2025-32, Internal Revenue Bulletin 2025-45.
- IRS, Publication 969 (2025), Health Savings Accounts and Other Tax-Favored Health Plans.
- Optum Financial, Medical Practitioner Statement of Medical Necessity.
- WEX, What is a letter of medical necessity and when do you need one?
- National Library of Medicine, ICD-10-CM K59.04.
- van der Schoot A, et al. The effect of fiber supplementation on chronic constipation in adults. Am J Clin Nutr. 2022.
This article is general information, not tax, legal, or medical advice. Plan rules vary and change. Confirm details with your plan administrator and a qualified professional.
Related reading
- Can You Use FSA or HSA for Fiber Supplements?
- Are Supplements FSA or HSA Eligible? What Qualifies and How to Use Your Account
- How Much Fiber Do Women Actually Need?
Seya Full Fiber
Most women fall short on fiber. Seya Full Fiber gives you 6 grams from three fibers in three small vegan gummies. Plant based, no gelatin, no sugar alcohols.
Shop Full Fiber
