Medically necessary
Updated September 30, 2026
Definition
Care or supplies needed to diagnose or treat an illness, injury, condition, disease, or its symptoms, and that meet accepted standards of medicine. Plans usually pay only for care they find medically necessary.
Medically necessary describes care you need to diagnose or treat a health problem, based on accepted standards of medicine. Health plans use this test to decide what they'll pay for.
You may see the phrase in a denial letter, a prior authorization decision, or your explanation of benefits (EOB). On an EOB, reason code 50 means your plan decided a service wasn't medically necessary.
A denial like this isn't the final word. Your doctor can often explain in a letter why you needed the care, and you can send it with an internal appeal. If your plan still says no, these denials can usually go to an external review. Our guide to denial codes on your EOB explains what to do next.
Related terms
Guides that use this term
- GuideDenial codes on your EOB, explainedWhat do CO-45, PR-1, and CO-16 mean? Look up common claim denial codes, learn who's responsible for each amount, and see what to do about each one.
- GuideInsurance didn't pay my medical bill: what to do nextInsurance didn't pay your medical bill? Find out why, match the denial code to the fix, and learn when to ask for a rebill and when to file an appeal.
- Start hereHow to appeal a health insurance denialA denied claim isn't the final word. Learn how to appeal an insurance denial, from internal appeal to external review, with deadlines for each plan type.
Sources
- Medically necessary (glossary), HealthCare.gov. Accessed September 30, 2026.
- External review (glossary), HealthCare.gov. Accessed September 30, 2026.
- Claim adjustment reason codes, X12. Accessed September 30, 2026.
This is general information, not legal or medical advice. Rules can depend on your plan and your state. Romi Care isn't an insurer, law firm, collection agency, or government program.