Why magnesium supplements qualify for HSA/FSA
Your reason for taking magnesium decides whether it's eligible. A Letter of Medical Necessity records a medical practitioner's recommendation to use the supplement as treatment for a specific health condition.
IRS Publication 502 defines medical expenses around the “diagnosis, cure, mitigation, treatment, or prevention of disease”. Its nutritional-supplements entry includes supplements when a medical practitioner recommends them as treatment for a specific medical condition diagnosed by a physician. Your LMN connects the magnesium you buy to that medical purpose.
The form on the bottle is a separate question. Glycinate, citrate and oxide are just different forms of magnesium, and a supplement with any of them follows the same letter route. A citrate laxative is an over-the-counter medicine with a different route, explained below. Our vitamins and supplements eligibility guide covers the broader supplement category; this page focuses on magnesium and its forms.
Which conditions qualify for a magnesium LMN?
Migraine, magnesium deficiency, chronic constipation and high blood pressure are some common conditions your provider can put in a magnesium letter, and magnesium has a known medical use for each. Your letter names your condition and how magnesium helps with it.
- Migraine: The idea is that magnesium cuts the release of pain-signaling chemicals and interrupts the brain signaling linked to aura. The American Migraine Foundation describes oral magnesium oxide as a migraine-prevention option and says the evidence is strongest for migraine with aura.
- Magnesium deficiency, or hypomagnesemia: Oral magnesium replaces magnesium that is too low in the body. MedlinePlus lists magnesium by mouth among the treatments for low blood magnesium, a direct match between the supplement and the condition.
- Chronic constipation: Magnesium oxide helps stool pass by retaining water in the bowel. A 2023 systematic review of randomized trials found that magnesium oxide improved stool frequency and consistency. Across its two magnesium oxide trials, 68% of people responded, compared with 19% in the control groups.
- High blood pressure, or hypertension: Magnesium helps set how tight or relaxed your blood vessels are, one of the ways your body controls blood pressure. A 2025 review in Hypertension combined 38 randomized trials with 2,709 people. Compared with placebo, magnesium lowered systolic pressure, the top number, by 2.81 mm Hg on average, and diastolic, the bottom number, by 2.05 mm Hg.
These four aren't the only ones. If your provider recommends magnesium for another condition and documents it in your letter, the same route applies.
How to get a Letter of Medical Necessity for magnesium
Either Crates or your own doctor can provide a Letter of Medical Necessity for magnesium.
- Through Crates, typically in under 24 hours. The short online health assessment takes about 2 to 3 minutes to fill out. A licensed provider reviews it and, if you qualify, issues your magnesium supplement letter, which is valid for 12 months and renews each year.
- Through your own doctor, a few days to a few weeks. Book a visit, explain that you want to use HSA/FSA funds for magnesium supplements, and ask your doctor to document how magnesium helps prevent, manage, or reverse your condition. Ask for the letter to be signed and dated. You could owe a copay for the visit.
How to buy magnesium with HSA/FSA funds
Buy your magnesium at a pharmacy, a grocery store, or an online retailer, then use the purchase receipt to get your funds back.
- Get your LMN first. Get your magnesium letter through Crates or your own doctor, using the steps above.
- Buy the supplement anywhere. Pay with your personal card, online or in store, and keep the itemized receipt showing the magnesium product and amount paid. An emailed order receipt works as a purchase record too.
- Get your funds back. Have Crates file the claim with one-click reimbursement, or upload the letter and receipt yourself. If the money comes from an HSA, keep both with your tax records.
Our HSA vs. FSA guide explains how reimbursement works for each account.
Which types of magnesium are HSA/FSA eligible?
The medical recommendation decides a magnesium supplement's eligibility, including the form and product it covers. Glycinate, citrate and magnesium oxide supplements all use the same LMN route. And the brand on the label doesn't change a thing.
| Magnesium form | What it is | HSA/FSA eligibility |
|---|---|---|
| Magnesium glycinate | Magnesium bound to glycine, also labeled bisglycinate | Yes, with an LMN |
| Magnesium citrate supplement | Magnesium bound to citric acid | Yes, with an LMN |
| Magnesium oxide supplement | The form studied for migraine and constipation | Yes, with an LMN |
Magnesium citrate can also be an over-the-counter medicine. Some magnesium citrate is a saline laxative for occasional constipation, like this one on DailyMed. OTC medicines are HSA/FSA eligible without a prescription under IRS Publication 969. That laxative needs no LMN; keep its itemized receipt. A daily magnesium citrate supplement uses the letter route above.
If your provider has you on vitamin D too, our vitamin D eligibility guide covers that one.
How much can you save on magnesium supplements?
Pay for magnesium with HSA/FSA funds and you keep up to 30% that would otherwise go to taxes. Spend $20 a month and that's $240 a year. With a combined rate near 30%, you skip $72 in taxes over the year.
These are example budgets, not current product prices. The combined rates reflect federal income tax, state income tax and payroll taxes where applicable. Each row shows annual supplement spending for repeat purchases.
Each column multiplies the purchase price by the illustrated tax rate:
| Example monthly spend | Annual purchase total | Tax savings at a combined 20% | Tax savings at a combined 30% |
|---|---|---|---|
| $10 | $120 | $24 | $36 |
| $20 | $240 | $48 | $72 |
| $30 | $360 | $72 | $108 |
| $40 | $480 | $96 | $144 |
The retailer still charges its listed price. Reimbursement just moves your own HSA/FSA money back to you; the savings come from that money being tax-free. Your actual benefit depends on your taxes and how you contribute, and provider or LMN fees are separate from these supplement-only examples.
