ICD-10-CM > S00-T88 > T36-T50 > T38 > T38.2 > T38.2X > T38.2X6 T38.2X6 Underdosing of antithyroid drugs Non-Billable/Non-Specific Codes T38.2X6A..., initial encounterT38.2X6D..., subsequent encounterT38.2X6S..., sequela