Letter of Medical Necessity
Everything you need to know about obtaining and using an LMN for FSA/HSA reimbursement
What is a Letter of Medical Necessity?
A Letter of Medical Necessity (LMN) is a formal document from a licensed healthcare provider that states a specific treatment, service, or product is medically necessary for the diagnosis, treatment, or prevention of a disease or medical condition.
For FSA and HSA purposes, an LMN serves as official documentation that certain items or services qualify as eligible medical expenses under IRS guidelines, even if they might not typically be considered medical expenses.
Popular Eligible Categories
Common items and services that typically require an LMN
Massage Therapy
For chronic pain or injury recovery
Acupuncture
Alternative pain management
Chiropractic Care
Spinal and musculoskeletal treatment
Exercise Equipment
Physical therapy and rehabilitation
Air Purifiers
Respiratory conditions and allergies
Special Diets
Medical conditions requiring specific nutrition
Weight Loss Programs
Obesity treatment prescribed by doctor
Service Animals
Trained animals for medical conditions
When Do You Need an LMN?
Dual-Purpose Items
Items that have both medical and personal use
Non-Traditional Treatments
Alternative therapies and specialized care
Specialized Equipment
Medical devices and adaptive equipment
Cosmetic Procedures
Medically necessary cosmetic treatments
What Should an LMN Include?
A proper Letter of Medical Necessity should contain:
- 1
Patient Information
Your full name, date of birth, and contact information
- 2
Healthcare Provider Details
Provider's name, credentials, contact information, and license number
- 3
Medical Diagnosis
Specific diagnosis or medical condition (with ICD-10 code if applicable)
- 4
Treatment Justification
Explanation of why the item/service is medically necessary
- 5
Item/Service Description
Clear description of the specific item, service, or treatment
- 6
Duration
How long the treatment or use of the item is expected to be necessary
- 7
Provider Signature
Original signature and date from the healthcare provider
How to Get an LMN
Schedule an Appointment
Contact your healthcare provider and explain that you need documentation for FSA/HSA reimbursement.
Discuss Your Needs
Explain the specific item or service you need and why you believe it's medically necessary for your condition.
Request the Letter
If your provider agrees it's medically necessary, request a formal letter on their letterhead with all required information.
Review and Submit
Review the letter for completeness and submit it with your FSA/HSA reimbursement claim along with receipts.
Real-World Examples
â Massage Therapy
You suffer from chronic back pain. Your doctor prescribes massage therapy as part of your treatment plan and provides an LMN stating the medical necessity. With the LMN, massage therapy becomes FSA/HSA eligible.
â Special Diet
You have celiac disease and need gluten-free foods. With an LMN from your doctor explaining the medical necessity, the incremental cost difference between gluten-free and regular foods may be eligible.
â Exercise Equipment
Your physical therapist prescribes specific exercise equipment for rehabilitation after an injury. An LMN documenting the medical necessity makes this equipment FSA/HSA eligible.
Important Reminders
- âĒAn LMN does not guarantee reimbursement - your plan administrator has final say
- âĒKeep copies of all LMNs with your tax records for at least 7 years
- âĒSome providers may charge a fee for writing an LMN
- âĒAlways check with your specific plan administrator about their LMN requirements
- âĒAn LMN is different from a prescription - both may be required for certain items