How to Use a Letter of Medical Necessity to Pay for Your Cold Plunge
Learn how a letter of medical necessity can make your cold plunge HSA or FSA eligible. We break down what qualifies, what to include and how to get approved.
A letter of medical necessity is the document that can turn your cold plunge purchase from a general wellness expense into a qualified medical expense, one your HSA or FSA can reimburse. Cold plunges typically run from a few hundred dollars for a DIY setup to several thousand for a full system, so reimbursement with pre-tax dollars is worth understanding if you're weighing the cost.
We're Plunge Crafters, and we're here to help you make the most of your cold plunge investment, starting with everything we offer. This guide walks through what a letter of medical necessity is, when you might need one and what a strong letter includes.
Key Takeaways
- A letter of medical necessity reclassifies a cold plunge as a qualified HSA or FSA medical expense. Without one, the purchase isn't reimbursable.
- A strong letter includes provider credentials, patient information, an ICD-10 diagnosis code, explicit mention of cold plunge equipment, clinical rationale, treatment duration and a signed, dated provider signature.
- Only a licensed provider who is actively treating you can determine whether cold therapy is appropriate for your condition.
- HSA funds roll over and can be reimbursed retroactively. FSA funds are subject to use-it-or-lose-it deadlines, which makes timing important.
- Most rejections come down to vague language, missing ICD-10 codes or unsigned letters, and most are fixable with revision and resubmission.
What Is a Letter of Medical Necessity?
A letter of medical necessity is a formal document written and signed by a licensed healthcare provider that establishes a specific medical need for a product or treatment. It's your doctor's written confirmation that a cold plunge is medically appropriate for your condition and not just a lifestyle preference.
For HSA and FSA purposes, the IRS requires that expenses be primarily for the prevention or alleviation of a physical or mental defect or illness. A cold plunge doesn't meet that standard on its own. The letter is what bridges the gap between a general wellness tool and IRS eligibility. Unlike a prescription, which authorizes a specific drug or treatment, a letter of medical necessity explains why a product is necessary for your individual situation.
When Do You Need One for a Cold Plunge?
Cold plunge systems are classified as general wellness equipment by default. Unlike a blood glucose monitor or a hearing aid, they aren't automatically recognized as a qualified medical expense by HSA and FSA administrators. A letter of medical necessity is what reclassifies the purchase.
The qualifying factor is an existing diagnosis your provider is actively managing, not the equipment itself. General interest in recovery or performance optimization won't satisfy the requirement. Before you purchase, contact your HSA or FSA plan administrator to confirm their specific acceptance policies, since these vary by plan. You can browse our cold plunge chillers and our complete DIY build kit while you sort out the paperwork, so you know what you're budgeting for.
Conditions Patients Sometimes Discuss With Their Provider
Every situation is different, and only your doctor can determine whether cold therapy is appropriate for you. Conditions that patients have raised with their providers when exploring a letter of medical necessity include chronic pain and fibromyalgia, inflammatory arthritis, delayed onset muscle soreness in a clinical rehab context, anxiety and mood-related concerns, multiple sclerosis fatigue and post-orthopedic surgery recovery. None of this is a claim that cold plunging treats or cures any of these conditions. It's simply a starting point for a conversation with a provider who knows your medical history.
What a Strong Letter of Medical Necessity Includes
A strong letter is specific, not vague, and vague letters are the most common reason claims get rejected.
It should come from a licensed, verifiable provider and include their credentials and contact information. It needs your name and date of birth, along with a diagnosis supported by an ICD-10 code, since administrators need a standardized basis for the claim.
It should name cold water immersion or a cold plunge system explicitly rather than referring generally to hydrotherapy, and it should include a short clinical rationale explaining how cold therapy fits your treatment plan. A duration of need matters too, since it signals ongoing use rather than a single purchase. Finally, the letter must be signed and dated. An unsigned or undated letter is rejected immediately.
How to Get a Letter of Medical Necessity
Start by scheduling an appointment with your primary care physician, sports medicine doctor or the specialist managing your relevant condition. Come prepared with documentation of your diagnosis and any prior treatment records.
During the appointment, have an honest conversation about cold therapy as part of your treatment plan and explain that you're pursuing HSA or FSA reimbursement. Most providers will include what's needed once they understand the requirements, but it helps to bring the list above so nothing gets missed.
Before you leave, review the letter to confirm it includes an ICD-10 code and names cold water immersion or your cold plunge system specifically. Then submit the letter along with your purchase receipt to your HSA or FSA administrator and keep copies of both for your own records.
Approval timelines vary by plan, though most decisions arrive within five to thirty business days. If your claim is denied, request a written explanation, work with your provider to address the specific gap and resubmit. Most denials are fixable with the right documentation.
What a Letter of Medical Necessity Looks Like
This is a sample for reference only. Your own letter must be written and signed by your licensed healthcare provider to be valid.
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Provider Name, MD/DO/NP Date: MM/DD/YYYY To Whom It May Concern, I am writing on behalf of my patient, Patient Name, whom I have treated for chronic inflammatory arthritis (ICD-10: M06.9). Based on my clinical assessment, I recommend daily cold water immersion therapy as part of his/her/their ongoing treatment plan. A home cold plunge system allows for consistent, daily treatment that clinic-based options cannot practically provide. I recommend daily sessions of three to ten minutes in water maintained at 45 to 55°F using a home cold plunge system, prescribed for a duration of twelve months with potential for renewal based on clinical progress. Signature: ___________________ |
What makes this example work is that it names a specific diagnosis with an ICD-10 code, identifies the equipment explicitly, includes a clinical rationale and states a duration. Those are exactly what plan administrators look for.
Common Mistakes That Get Letters Rejected
Vague language is the biggest one. Letters that reference hydrotherapy in general without naming cold plunge equipment or citing a diagnosis are routinely rejected. A missing ICD-10 code leaves administrators with nothing standardized to verify, and a letter without a duration statement reads as a one-time want rather than an ongoing medical need.
Unsigned or undated letters aren't valid medical documents. Submitting a letter without your purchase receipt will also hold up a claim, and a letter from a provider with no clinical history treating your condition is a red flag for administrators.
HSA vs. FSA: Which Works Best for a Cold Plunge Purchase
Both accounts can reimburse a cold plunge purchase, but they work differently.
An HSA is only available with a high-deductible health plan. Funds roll over year to year with no deadline pressure, balances can be invested and grow tax-free, and you can reimburse yourself retroactively for any expense incurred after the account was opened.
An FSA is available through most employer-sponsored plans regardless of deductible type, but it's subject to use-it-or-lose-it rules, so unspent funds may be forfeited at year end. Your full annual election is available on day one, which makes early-year purchases easier, and some plans offer a grace period or a limited rollover allowance. Check with your plan administrator or IRS.gov for current limits.
If you're working against an FSA deadline, a cold plunge backed by a letter of medical necessity is a qualified use of year-end unspent funds. If you're building a DIY system with components like our ozone injector bundle, keep itemized receipts for each part, since administrators may ask for documentation that every component serves the medically necessary purpose. Whichever account you're using, contact your plan administrator before purchasing to confirm their acceptance policies.
FAQs About Letters of Medical Necessity for Cold Plunges
What is a letter of medical necessity for a cold plunge?
A formal document written by a licensed healthcare provider establishing that you need cold water immersion therapy to treat a specific medical condition, which allows your HSA or FSA administrator to classify the purchase as a qualified medical expense.
How do I get a letter of medical necessity for my cold plunge?
Schedule an appointment with your physician or a relevant specialist, explain that you're using cold therapy to manage a diagnosed condition and ask them to write a letter that includes your ICD-10 code, clinical rationale and recommended duration. Telehealth platforms are also an option, but confirm acceptance with your plan administrator first.
Why do I need a letter of medical necessity instead of just using my HSA or FSA card?
Cold plunges aren't automatically classified as qualified medical expenses. Without a letter, your administrator can deny the expense or flag it as non-qualified, which could result in taxes and penalties on the withdrawn funds.
How long does it take to get approved after submitting a letter of medical necessity?
Most decisions arrive within five to thirty business days. If denied, you have the right to request a written explanation and resubmit a revised letter addressing the specific gap.
Can any doctor write a letter of medical necessity for a cold plunge?
Any licensed healthcare provider can write one, including your primary care physician, a sports medicine doctor or a rheumatologist. Physical therapists may qualify in some cases, though this varies by state and plan. The key requirement is that the provider is actively treating you for the relevant condition.
If you have questions about which system fits your situation while you sort out reimbursement, our contact page is the fastest way to reach us, and our HSA/FSA eligibility page covers the basics of how the process works.
We also work with Truemed to help simplify this process, connecting you with an independent licensed clinician who can review your eligibility and issue a letter of medical necessity if you qualify.
Start Your Cold Plunge Practice Today
Working through the paperwork for a letter of medical necessity takes some patience, but it shouldn't stand between you and starting your cold plunge practice. While you wait on approval, you don't have to choose between an overpriced luxury tub and a janky setup pieced together from mismatched parts.
Our complete DIY cold plunge build kit gives you everything you need for a clean, reliable setup, and our cold plunge chillers are built to get your water cold and keep it there without the guesswork.
Whether your reimbursement comes through now or later, you'll have a system that's ready for daily use from day one.
