ICD-10-CM > S00-T88 > T36-T50 > T36 > T36.4 > T36.4X > T36.4X6 T36.4X6 Underdosing of tetracyclines Non-Billable/Non-Specific Codes T36.4X6A..., initial encounterT36.4X6D..., subsequent encounterT36.4X6S..., sequela