CO-151: Frequency of services not supported
UPDATED JULY 2026 · U.S. PLANS · NOT LEGAL OR MEDICAL ADVICE
The payer thinks you received this service too often (e.g., imaging repeated 'too soon'). Frequency rules bend to clinical reality — with documentation.
CO-151 at a glance
- Code group: CO — Contractual Obligation — in-network providers generally cannot bill you for CO adjustments.
- Who usually fixes it: You (the member).
- Worth appealing? Yes — commonly appealed.
What to do about a CO-151 denial
- Ask which frequency policy applies and what interval it expects.
- Have your doctor document why the repeat service was clinically necessary at that interval.
- Appeal with that documentation; frequency denials are regularly overturned.
Best next read: “Not medically necessary” denials — the full guide (with a free letter template) for this denial type.
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