How to Appeal a Medical Necessity Denial (CO-50)
Insurance denied your claim as 'not medically necessary' (CO-50)? Learn what it means, why insurers use it, and how to write a winning appeal letter with AI in minutes.
What does CO-50 mean?
A CO-50 denial, also called a 'not medically necessary' denial, means your insurer decided the treatment, procedure, or medication your doctor ordered does not meet their clinical criteria for coverage. This is one of the most common clinical denial reasons patients encounter.
Why insurers issue CO-50 denials
Insurers issue CO-50 denials based on internal clinical coverage policies that are often stricter than actual medical standards of care. Common triggers include treatments your doctor has ordered that the insurer considers 'experimental,' drugs prescribed off-label, procedures done more frequently than the insurer's guideline allows, or services where the insurer believes a less expensive alternative exists.
Appeal strategy
Obtain a letter of medical necessity from your treating physician citing peer-reviewed clinical literature. Reference your insurer's own clinical policy document and identify any discrepancy. Cite your state's insurance code requiring benefit determinations to be based on generally accepted standards of medical practice.