To get your FSA to reimburse a dual-purpose item, you need a licensed healthcare provider to write a letter of medical necessity that ties the specific item to a diagnosed condition, and you submit that letter alongside an itemized receipt. Vitamins, massage therapy, exercise equipment, weight-loss programs, orthopedic shoes, and similar purchases sit in a gray zone because a healthy person might buy them too. The letter is what moves them from personal spending into reimbursable medical care under Section 213(d) of the Internal Revenue Code.1Office of the Law Revision Counsel. 26 USC 213 – Medical, Dental, Etc., Expenses
What Counts as a Dual-Purpose Item
The IRS defines qualifying medical care as amounts paid for the diagnosis, cure, mitigation, treatment, or prevention of disease, or for affecting a structure or function of the body. A product bought only for medical reasons clears that bar on its own. A dual-purpose item is one a healthy person might also buy: a treadmill, a multivitamin, a massage, a standing desk.
Publication 502 draws the line by saying an expense “merely beneficial to the general health of an individual” is not medical care.2Internal Revenue Service. Publication 502, Medical and Dental Expenses The practical test: would you have bought this if you didn’t have the condition? If yes, it doesn’t qualify. If a physician diagnosed a specific problem and recommended this exact item to treat it, the same purchase becomes eligible.
One boundary worth naming. The CARES Act permanently removed the prescription requirement for over-the-counter drugs and made menstrual products eligible, for purchases after December 31, 2019.3Internal Revenue Service. IRS Outlines Changes to Health Care Spending Available Under CARES Act Pain relievers, allergy medicine, and cold remedies no longer need a letter. Supplements, vitamins, and non-drug items still do when they have a personal-use component.
What the Letter Must Include
The IRS doesn’t publish a standardized template, but administrators consistently look for the same elements. A strong letter establishes a clear chain from diagnosed condition to recommended item to clinical benefit.
- Your full name, date of birth, and any member ID the administrator requires.
- A specific medical diagnosis, stated precisely. Providers often include the ICD-10 code; what matters is that the condition is clearly identified.
- The specific item, dosage, or service recommended. Not “supplements” but “ferrous sulfate 325 mg daily.”
- Clinical rationale explaining why this item is medically necessary for your condition, not just beneficial for general health.
- Duration of need, whether short-term or ongoing.
- The provider’s printed name, credentials, and signature.
Many FSA administrators host their own template on the member portal. Using their form tends to move things faster because every field a reviewer checks is already filled in. A freeform letter works too if it covers each element above. A vague letter saying “patient needs vitamins for health” gets denied. One saying “patient has been diagnosed with iron-deficiency anemia and requires daily ferrous sulfate supplementation at 325 mg to restore adequate iron levels” gives the reviewer what the rules require.
Who Can Sign the Letter
Publication 502 defines qualifying providers broadly, covering physicians, surgeons, dentists, and other medical practitioners, and references licensed healthcare practitioners for certain expenses.2Internal Revenue Service. Publication 502, Medical and Dental Expenses Nurse practitioners, physician assistants, licensed psychologists, and chiropractors generally can write letters for items within their scope of practice.
Certain expenses specifically require a physician. Publication 502 calls for a physician’s diagnosis for weight-loss programs, a physician’s prescription for health institute treatment, and a doctor’s recommendation for special education expenses. If you’re not sure whether your provider’s credential is sufficient for a particular expense, ask the administrator before you submit. A denial over the wrong provider type is avoidable.
Common Items and When They Qualify
These are the categories that most often need a letter.
- Vitamins and supplements: ineligible for general health, eligible when a practitioner recommends them to treat a specific diagnosed condition, such as iron for anemia or vitamin D for a documented deficiency.
- Weight-loss programs: eligible only when treating a specific disease a physician has diagnosed, such as obesity, hypertension, or heart disease. A program for general fitness or appearance does not qualify.4Internal Revenue Service. Revenue Ruling 2002-19
- Special diet food: even inside a qualifying weight-loss program, reduced-calorie food that substitutes for what you’d normally eat is not eligible. Special food qualifies only when it doesn’t satisfy normal nutritional needs and a physician substantiates it.
- Massage therapy: eligible when prescribed for a diagnosed musculoskeletal condition or chronic pain disorder. A relaxation massage does not qualify.
- Exercise equipment: a treadmill or stationary bike bought on a doctor’s recommendation to treat a diagnosed cardiac condition or for rehabilitation can qualify. The same equipment for general fitness cannot.
- Wigs: eligible when purchased on a physician’s advice for the mental health of someone who has lost all hair from disease.
- Orthopedic shoes: only the amount exceeding the cost of ordinary shoes qualifies, and only when prescribed for a foot condition.
GLP-1 medications like semaglutide or tirzepatide prescribed for obesity fit the same framework as any other prescription treating a diagnosed disease. Confirm coverage with the plan administrator, since some plans lag on newer treatments.
Submitting the Claim
You file through the administrator’s portal or app. The package has two parts: the letter and an itemized receipt. The receipt has to show the date, the merchant or provider, a description of what you bought, and the amount paid.
IRS regulations require independent third-party substantiation for every FSA expense. Credit card statements and bank records don’t count because they lack item-level detail, and self-certification is prohibited.5Internal Revenue Service. Chief Counsel Advice 202317020 – FSA Substantiation Requirements Processing speeds vary. Straightforward claims resolve in a few business days; dual-purpose claims often take longer because a reviewer has to read the medical documentation.
The Letter Expires With the Plan Year
Most administrators treat a letter of medical necessity as valid only through the end of the current plan year. If you have a chronic condition and buy the same item year after year, you need a fresh letter each plan year. The renewal confirms the medical need is still current and the treatment still appropriate. Build it into your annual physical so a lapse doesn’t stall reimbursement in January.
If Your Claim Is Denied
Common reasons include missing documentation, an expired letter, a mismatch between the receipt and the item described, or a reviewer who found the medical rationale insufficient. Under federal regulations, the written denial has to give you the specific reason, the plan provisions relied on, a description of any additional information that would fix the claim, and an explanation of your appeal rights, including your right to sue under ERISA if the appeal fails.6eCFR. 29 CFR 2560.503-1 – Claims Procedure When the denial rests on medical judgment, the notice must include the clinical reasoning or offer to provide it on request.7U.S. Department of Labor. Benefit Claims Procedure Regulation FAQs
You have at least 180 days from the denial to file a formal appeal. For post-service FSA claims, the administrator has 60 days to respond. Use the window. If the denial cited insufficient documentation, go back to your provider for a more detailed letter connecting the diagnosis to the item. If the reviewer misread the item’s purpose, write a short cover letter walking through the chain from condition to recommendation to purchase.
What Happens If You Skip the Letter
If your FSA reimburses something that doesn’t qualify under Section 213(d), the reimbursement becomes taxable income to you.8Internal Revenue Service. Publication 969, Health Savings Accounts and Other Tax-Favored Health Plans You lose the tax benefit and may owe income tax you hadn’t planned for.
The stakes go further at the plan level. IRS regulations prohibit FSA plans from using self-certification, sampling claims instead of reviewing all of them, or waiving substantiation below a dollar threshold. A plan that has been systematically lax about documentation, including letters of medical necessity for dual-purpose items, can be disqualified as a cafeteria plan. If that happens, every benefit elected under the plan becomes taxable income for all participants, not just those whose claims were problematic. That’s why administrators enforce substantiation the way they do, and why pushing a questionable item through without a letter isn’t worth the risk.