Letter of Medical Necessity (LMN)

Last Updated: February 21, 2019

Definition - What does Letter of Medical Necessity (LMN) mean?

A letter of medical necessity (LMN) is a letter issued by a person's physician describing why a requested treatment is necessary. LMNs are often used to justify a request for specific medications, medical equipment, or therapy.

These letters may be required by an individual's private insurer or other agency before payment will be authorized for the requested treatment. Letters of medical necessity may also be needed by individuals traveling with medical equipment or medications. The LMN demonstrates to customs and other officials that the person requires the item and should be permitted to keep it with them. In some cases, a LMN may be provided to an employer to explain a specific accommodation requested or an out of the ordinary medical situation.

A letter of medical necessity may also be called a doctor's statement.

WorkplaceTesting explains Letter of Medical Necessity (LMN)

Most letters of medical necessity will include a clear statement by a person's physician explaining the need for a particular treatment or device. The letter will state that the treatment is necessary and reasonable.

A physician writing such a letter to justify compensation for the treatment should include a clear indication that the treatment is consistent with the current standards of practice. Sometimes, insurers or government agencies will require that a physician also indicate that other treatment options have been evaluated and rejected or that such options were previously tried without success.

A letter of medical necessity is sometimes required when an employee seeks reimbursement for expenses from his or her health care flexible spending account (FSA).

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