What is a Letter of Medical Necessity?

What is a Letter of Medical Necessity

A Letter of Medical Necessity (LMN) is a formal document issued by a licensed clinician on Truemed’s provider network. It attests that a specific product or service is medically necessary to treat, mitigate, or prevent a diagnosed health condition.

When you complete Truemed’s clinical intake survey, a licensed provider reviews your health information and, if appropriate, issues an LMN on your behalf. This document is then on file to support your HSA or FSA reimbursement or direct payment.

LMNs are product and merchant specific. The clinician is attesting that a particular type of product, from a particular merchant, is medically necessary for your condition.

Why an LMN is required

The IRS defines qualifying medical expenses under Section 213(d) as costs related to “the diagnosis, cure, mitigation, treatment, or prevention of disease, and for the purpose of affecting any part or function of the body.” Many health products can meet this definition, but HSA and FSA administrators require documentation to confirm it.

An LMN bridges that gap. It connects a product to a qualifying medical purpose, giving your plan administrator the documentation needed to approve the expense. Without one, a purchase that could otherwise qualify may be flagged or denied.

LMN validity & expiration

LMNs issued through Truemed are typically valid for 12 months from their issue date. Any eligible purchases made within that window can be reimbursed using HSA or FSA funds, as long as sufficient funds are available.

When your LMN expires, the documentation is no longer valid for new purchases. To renew, reach out to Truemed support at support@truemed.com. The team will send you a link to retake the clinical intake survey, and a clinician will review your updated information. If medical necessity is still supported, a new LMN will be issued.

For one-time purchases (like a piece of fitness equipment), renewal isn’t necessary unless you plan to make a similar purchase after your LMN has lapsed. For ongoing purchases, such as supplements, you’ll need to renew annually to keep your documentation current.

Using one LMN across multiple merchants

Each LMN is specific to the merchant and products it was issued for. Technically, an LMN issued for one business cannot be transferred or applied to a different merchant’s products or services.

This is a critical step in ensuring that your purchases are compliant with IRS guidelines. The IRS requires that an LMN directly relates to the product or service being purchased. If you plan to use HSA or FSA funds at multiple merchants, you’ll need a separate LMN for each one. Truemed makes this process straightforward, but each merchant requires its own documentation to keep your reimbursements fully compliant.

If you have questions about obtaining an LMN for a specific merchant, contact support@truemed.com.

Recurring LMN for subscriptions

If you have an ongoing subscription, such as a monthly supplement order or a coaching program, your LMN covers purchases made during its 12-month validity period. Once it expires, you’ll need a renewed LMN to continue using HSA or FSA funds for that subscription.

To stay on top of this, check your LMN’s expiration date and reach out to Truemed support within 30 days of that date. The team will send you a new intake survey, a clinician will review your health information, and a renewed LMN will be issued if medical necessity is still supported.

Letting your LMN lapse before renewing means purchases made after the expiration date won’t have the documentation needed for reimbursement, so it’s worth renewing proactively.

Using an external LMN or Dr’s Note

If you already have a letter of medical necessity or a doctor’s note from your own healthcare provider, you may wonder whether it can substitute for a Truemed-issued LMN.

In general, external letters and notes must meet specific requirements to be accepted by HSA and FSA administrators. These include details about the diagnosed condition, the specific product or service being recommended, and the clinician’s credentials and signature. Many standard doctor’s notes or prescriptions don’t include all of the required elements.

Because each situation is different, Truemed’s support team can help assess whether an existing document meets the necessary requirements. Reach out to support@truemed.com with a copy of your documentation, and the team will let you know if it qualifies or if a Truemed-issued LMN would better serve your needs.