How long does a letter of medical necessity last?
It depends on the plan administrator. Many accept a letter for a plan year; some ask for a new one for each purchase or condition change.
There is no single national rule. Administrators set their own requirements for how long a letter remains valid and which expenses it covers.
Ask your administrator before relying on an older letter, and ask your clinician for a new one if your condition or treatment plan changes.
Pending clinician sign-off. General education only, not medical, tax, or legal advice. Your plan administrator decides eligibility.