Do You Need a Letter of Medical Necessity for Red Light Therapy?

Short answer: most FSA/HSA-eligible red light therapy devices don't need a Letter of Medical Necessity to purchase — if it rings up clean at checkout or your manual claim gets approved, you're done. But if your plan administrator flags the purchase, denies a reimbursement claim, or you're buying specifically to treat a diagnosed condition, a short letter from your doctor is usually the fastest way to get your money back.

If you've ever submitted a red light therapy receipt to your FSA or HSA and gotten a "needs more documentation" email back, you're not alone. It's confusing, because red light devices are widely marketed as FSA/HSA eligible — and they often are. The letter of medical necessity only enters the picture in a specific, narrower set of situations. Here's how to tell which one you're in.

What is a Letter of Medical Necessity?

A Letter of Medical Necessity, or LMN, is a short, signed statement from a licensed healthcare provider that names a specific medical condition and explains why a product or service is needed to treat, manage, or prevent it. It's the document that turns a "dual purpose" item — something that could be used for general wellness or for a real medical condition — into a legitimate, reimbursable medical expense in the eyes of your FSA or HSA administrator.

The IRS doesn't use the phrase "Letter of Medical Necessity" anywhere in its own publications, but the concept comes straight from how it defines a medical expense. IRS Publication 502 limits reimbursable medical expenses to costs for the "diagnosis, cure, mitigation, treatment, or prevention of disease," and specifically excludes anything that is "merely beneficial to general health." An LMN is how you document that your purchase falls on the treatment side of that line, not the general-wellness side.

Do you need one to buy red light therapy with your FSA or HSA?

Usually, no — not at the point of purchase. Most FSA/HSA-eligible AWA devices are coded so your card is accepted automatically at checkout, the same way it would be for a heating pad or a knee brace. If your card swipes clean, you don't need to do anything else. Save your itemized receipt in case your plan asks for it later, but there's no letter required up front.

Where things get more complicated is reimbursement claims — meaning you paid out of pocket and are now asking your FSA or HSA to pay you back. Some plan administrators automatically approve red light therapy as a general wellness device; others treat it as dual-purpose and want to see documentation tying it to a diagnosed condition before they release funds. You usually only find out which camp your plan falls into after a claim gets kicked back.

When does a red light therapy purchase actually need an LMN?

An LMN becomes useful in a few specific situations: your reimbursement claim was denied or flagged as "needs more information," your plan document specifically lists light therapy devices as requiring extra substantiation, you're using a Limited Purpose FSA or a Dependent Care FSA account that has stricter eligibility rules, or you simply want a stronger paper trail in case of an IRS audit down the road.

It also matters what you're treating. Reimbursement is far easier to defend when the letter names a specific, diagnosable condition — joint pain from arthritis, muscle soreness from physical therapy, diabetic neuropathy, psoriasis, or post-surgical healing, for example — rather than a general goal like "wellness" or "anti-aging." A provider can write a defensible letter around a diagnosis. It's much harder to write one around a feeling.

What should a red light therapy LMN include?

A useful LMN is short and specific. At minimum, it should include the patient's name, the diagnosed condition being treated, an explanation of how red light therapy or photobiomodulation helps manage that condition, the recommended device type or frequency of use, an expected duration of treatment, and the provider's signature, license information, and the date. A vague note that just says "patient may benefit from red light therapy" is much weaker than one that says "patient has diagnosed knee osteoarthritis; red light therapy to the affected joint, 15–20 minutes, 3–5 times weekly, for 90 days, is recommended as an adjunct to current treatment."

The evidence a provider can point to is real, even if it's not a guarantee. A 2025 randomized controlled trial published in Lasers in Medical Science found that patients with knee osteoarthritis who received photobiomodulation reported significantly greater reductions in pain and stiffness than those in placebo or control groups. A separate research review indexed on PubMed summarizing current studies on photobiomodulation for knee osteoarthritis reached a similar conclusion: it's being studied as a legitimate adjunct for joint pain management, not a fringe idea. That's useful context for a provider deciding whether to put their name on a letter — but it's your doctor's call, not something a store can promise on your behalf.

How do you actually get one from your doctor?

Ask directly. Most people are surprised at how simple this conversation is — providers write LMNs for dual-purpose items regularly, for everything from air purifiers to massage devices. Bring up the specific condition you want treated, mention that you're asking for FSA/HSA purposes, and offer to bring in the product page or spec sheet so they can reference it in the letter. Many providers will draft one during a normal visit at no extra cost; some charge a small fee for paperwork done outside an appointment. If your provider isn't familiar with red light therapy, a one-page summary of the device (which AWA includes with every FSA/HSA-eligible product) can help them write a more specific letter.

What happens if your claim gets denied without one?

Most FSA and HSA administrators will tell you exactly why a claim was denied and what would fix it. If the reason is "dual-purpose item, documentation required," that's your cue to get an LMN and resubmit — most plans allow you to appeal or resubmit a denied claim rather than losing the funds outright. If you're not sure why a claim was denied, call your plan administrator before assuming the purchase isn't eligible at all; it may just need the extra paperwork, not a refund back to your bank account.

Frequently asked questions

Does every FSA/HSA purchase of red light therapy need a Letter of Medical Necessity?

No. Most card purchases of FSA/HSA-eligible AWA devices go through without any extra documentation. An LMN is a backup tool for reimbursement claims that get flagged or denied.

How long is a Letter of Medical Necessity valid?

It varies by plan, but many administrators treat an LMN as valid for one year or for the duration stated in the letter itself. If you plan to keep using the device to manage an ongoing condition, ask your provider to note that in the letter.

Can a nurse practitioner or physical therapist write an LMN, or does it have to be a physician?

Most plans accept a letter from any licensed healthcare provider who can diagnose and treat the condition in question, including nurse practitioners, physician assistants, physical therapists, and chiropractors, depending on your state's scope-of-practice rules. Check with your plan administrator if you're unsure.

Does AWA provide Letters of Medical Necessity?

No — an LMN has to come from your own licensed healthcare provider, since it's their professional judgment about your specific diagnosis. AWA can provide product information and specs to help your provider write a more detailed letter, but we can't write or sign the letter itself.

What if my FSA plan is a Limited Purpose FSA?

A Limited Purpose FSA (LPFSA) generally only covers dental and vision expenses unless you're also contributing to an HSA, so a general red light therapy device usually won't qualify under an LPFSA no matter what documentation you provide. Check your plan's specific rules before buying.

Is it worth getting an LMN just in case?

If you're using red light therapy to manage a real, diagnosed condition, it costs you nothing but a conversation with your provider and gives you a stronger claim if anything is ever questioned. If you're using it purely for general wellness, an LMN likely won't change your eligibility either way.

Whatever situation you're in, the goal is the same: get the paperwork that matches how you're actually using the device. That's usually enough to keep your pre-tax dollars working the way they're supposed to. For the full rules on FSA/HSA eligibility, deadlines, and which AWA devices qualify, see our FSA/HSA eligibility guide, or browse the full FSA/HSA-eligible collection.

Lights on, pain off.

This article is for general education and is not medical advice. Red light therapy devices are intended for general wellness and are not intended to diagnose, treat, cure, or prevent any disease. Always check with a qualified healthcare provider before starting a new therapy.