July 2026 · Ashley Shaw, FNP-BC
Can You Use Your HSA or FSA for Functional Medicine and Longevity Care?
One of the most practical questions I hear from new and prospective patients is about paying for care: functional medicine, advanced testing, and longevity work often fall outside traditional insurance, and people want to know whether they can use the tax-advantaged health dollars they've already set aside. The short answer is often yes – but the details matter, and understanding them can save you real money.
A quick note before we start: I'm a nurse practitioner, not a tax advisor, and this article is general educational information, not tax advice. Your HSA or FSA administrator has the final say on any specific expense, so it's always worth a quick call to them.
HSA vs. FSA: a quick refresher
Both accounts let you pay for qualified medical expenses with pre-tax dollars, which effectively discounts your care by your tax rate. They work a little differently:
A Health Savings Account (HSA) is available to people enrolled in a qualifying high-deductible health plan. The money is yours – it rolls over year to year, can be invested, and stays with you even if you change jobs. For 2026, you can contribute up to $4,400 for self-only coverage and $8,750 for family coverage. After age 65, HSA funds can be used for anything (though non-medical withdrawals are taxed as income).
A Flexible Spending Account (FSA) is offered through an employer. For 2026, you can contribute up to $3,400. The main catch is the "use it or lose it" rule: FSA funds generally must be spent within the plan year, though some employers allow a carryover (up to $680 for 2026) or a short grace period. That deadline is exactly why many people look for eligible ways to use remaining funds before year-end.
What's typically eligible
The IRS standard is whether an expense diagnoses, treats, mitigates, or prevents a medical condition – rather than supporting general wellness. Under that standard, many of the services in a functional medicine practice are commonly eligible, including:
Office visits and consultations with a licensed provider, diagnostic lab testing ordered to evaluate a condition, prescribed medications, and medical procedures. These are generally treated like any other medical care, because they involve a licensed provider evaluating and managing your health.
The gray area: supplements, programs, and wellness services
Here's where it gets nuanced. The IRS draws a firm line between treating a condition and promoting general health. A daily multivitamin "to feel healthier" is considered a personal expense and isn't eligible. But a supplement recommended to treat a documented, diagnosed condition can qualify – the classic example being vitamin D prescribed for a lab-confirmed deficiency, or a specific supplement that's part of a care protocol for a diagnosed condition.
The same logic applies to things like weight-loss programs and certain wellness services: they may become eligible when they're recommended to treat a specific diagnosed condition rather than for general wellbeing. The deciding factor usually isn't the item itself – it's the medical context and the documentation behind it.
The key tool: a Letter of Medical Necessity
For those gray-area expenses, the document that often makes the difference is a Letter of Medical Necessity (LMN). This is a letter from a licensed provider – such as a nurse practitioner, physician, or physician assistant – explaining why a specific product or service is medically necessary to treat or prevent a diagnosed condition.
A strong letter generally includes your diagnosis, the specific recommended treatment or product, the clinical reason it's necessary, and how long it's needed. It connects a real, documented condition to a specific intervention – which is exactly what an HSA or FSA administrator is looking for. What an LMN can't do is turn a general wellness purchase into an eligible one; the medical necessity has to be genuine and documented.
This is one quiet advantage of working with a functional medicine practice that does thorough testing: when a recommendation is grounded in your labs and a documented diagnosis, the clinical justification for an LMN is already there.
Practical tips
A few things that make the process smoother: confirm eligibility with your HSA or FSA administrator before assuming an expense qualifies, since policies vary. Keep good records – itemized receipts and any letters of medical necessity – in case you're ever asked to substantiate a claim. If you have an FSA with a year-end deadline, plan eligible care and testing before you forfeit unused funds. And ask your provider directly whether a Letter of Medical Necessity is appropriate for a given recommendation.
How this works at Solveris
At Solveris, much of what we do – consultations, advanced lab testing, and evidence-based treatment of diagnosed conditions – falls into the category of care patients commonly pay for with HSA or FSA funds. When a supplement or program is part of your documented treatment plan, we're glad to discuss whether a Letter of Medical Necessity is appropriate for your situation. Our goal is simply to help you get the most value from the health dollars you've already set aside. For more on what care typically costs, see our guide to what functional medicine testing costs.
This article is for general educational purposes only and is not tax, legal, or medical advice. HSA and FSA eligibility rules are set by the IRS and administered by your account provider, who determines whether a specific expense qualifies. Contribution limits cited are for 2026 and may change. Please consult your account administrator and a qualified tax professional about your individual situation.