The short answer
Melatonin is not FSA eligible. The FDA classifies it as a dietary supplement, and SIGIS classifies dietary supplements as dual-purpose by default — meaning they’re not eligible without a Letter of Medical Necessity from a doctor.
But here’s the part most people miss: Unisom is FSA eligible. Same goal (helping you sleep), totally different regulatory category, totally different FSA outcome. If you want to spend FSA dollars on a sleep aid, the answer is OTC drug-class sleep aids — not supplements.
The supplement vs. drug distinction
This is the rule that explains everything:
| Type | Regulated As | FSA Eligibility |
|---|---|---|
| Melatonin | Dietary supplement | Not eligible (LMN required) |
| Valerian root | Dietary supplement | Not eligible (LMN required) |
| Magnesium “sleep” formulas | Dietary supplement | Not eligible (LMN required) |
| Herbal sleep blends | Dietary supplement | Not eligible (LMN required) |
| Unisom (doxylamine) | OTC drug | Always eligible |
| ZzzQuil (diphenhydramine) | OTC drug | Always eligible |
| Benadryl (diphenhydramine) | OTC drug | Always eligible |
| Aleve PM, Tylenol PM | OTC drug combo | Always eligible |
The pattern: anything sold as a drug with an FDA Drug Facts label is eligible. Anything sold as a supplement with a Supplement Facts label is not.
You can spot the difference instantly. Pick up a bottle of melatonin and you’ll see “Supplement Facts” on the back. Pick up a bottle of Unisom and you’ll see “Drug Facts.” That single label is what determines FSA eligibility.
Why the rule is structured this way
OTC drugs go through FDA review and approval before they can make therapeutic claims. The active ingredient (doxylamine in Unisom, diphenhydramine in ZzzQuil) is studied, dosed, and labeled with specific medical use cases.
Supplements are regulated under DSHEA (Dietary Supplement Health and Education Act) and don’t go through pre-market approval. They can’t legally claim to treat or cure conditions — only to “support” general health functions. That regulatory difference is what SIGIS uses to classify them as dual-purpose.
It doesn’t matter that melatonin works for many people, or that doctors recommend it. The FDA classification controls the FSA eligibility, and melatonin is firmly in the supplement category.
What sleep products you can actually buy with FSA
Always eligible (no LMN needed):
- Unisom SleepGels — doxylamine 50mg
- Unisom SleepTabs — doxylamine 25mg
- ZzzQuil LiquiCaps and Liquid — diphenhydramine 50mg
- Vicks ZzzQuil PURE Zzzs LiquiCaps (the diphenhydramine versions, not the melatonin versions)
- Tylenol PM — acetaminophen + diphenhydramine
- Advil PM — ibuprofen + diphenhydramine
- Aleve PM — naproxen + diphenhydramine
- Sleep masks (general OTC eye masks marketed for sleep)
Not eligible by default:
- Any melatonin product (Natrol, Nature Made, OLLY Sleep, Vitafusion Sleep, ZzzQuil PURE Zzzs gummies)
- Magnesium glycinate or magnesium for sleep
- Valerian root, ashwagandha, L-theanine, GABA supplements
- “Sleep tea” blends and herbal capsules
- CBD products marketed for sleep
Note the trap with ZzzQuil: the brand sells two product lines. The original ZzzQuil LiquiCaps and Liquid contain diphenhydramine and are eligible. ZzzQuil PURE Zzzs gummies contain melatonin and are not eligible. Same brand, opposite outcomes — check the active ingredient before assuming.
The LMN path for melatonin
If you specifically want melatonin and have a documented sleep disorder, you can pursue a Letter of Medical Necessity. Common scenarios where plans approve melatonin LMNs:
- Insomnia diagnosed by a sleep specialist or PCP
- Circadian rhythm disorders (delayed sleep phase, shift work disorder)
- Pediatric sleep disturbance related to autism or ADHD
- Jet lag for occupations with frequent international travel (less commonly approved)
The LMN must come from a licensed provider, name the diagnosis, and specifically recommend melatonin. Submit it to your plan administrator before purchasing. Approval is plan-dependent.
What this means for your spend-down plan
If sleep is the goal, swap melatonin for Unisom or ZzzQuil. Same shelf at the pharmacy, same outcome at bedtime, completely different FSA outcome. A bottle of Unisom SleepTabs runs $10–15 and stocks well — the kind of low-stakes purchase that adds up when you’re trying to clear a small remaining balance.
For the broader picture of what’s eligible in the medication aisle, see the OTC medications category page and the article on why most vitamins aren’t eligible either.
Don’t let the balance go to waste
Use the balance tool to build a bundle that fits your remaining balance — sleep aids, pain relief, allergy medication, and other OTC essentials make some of the easiest spend-down purchases in the catalog.