ICD-10-CM > S00-T88 > T36-T50 > T39 > T39.4 > T39.4X > T39.4X6 T39.4X6 Underdosing of antirheumatics, not elsewhere classified Non-Billable/Non-Specific Codes T39.4X6A..., initial encounterT39.4X6D..., subsequent encounterT39.4X6S..., sequela