ICD-10-CM > S00-T88 > T36-T50 > T40 > T40.3 > T40.3X > T40.3X6 T40.3X6 Underdosing of methadone Non-Billable/Non-Specific Codes T40.3X6A..., initial encounterT40.3X6D..., subsequent encounterT40.3X6S..., sequela