ICD-10-CM NOS Codes: When to Use "Not Otherwise Specified"

NOS (Not Otherwise Specified) codes are used when clinical documentation lacks the detail to assign a more specific code, but the condition is evident. They indicate a diagnosis is present but not fully characterized.

Guidance

• Use only when specificity cannot be achieved despite reasonable query efforts.
• Avoid defaulting to NOS; pursue clarification first.
• NOS codes may affect reimbursement and data granularity.

ICD-10-CM has fewer NOS categories than ICD-9-CM, favoring greater specificity.