ATC code H03 Thyroid therapy is a therapeutic subgroup of the Anatomical Therapeutic Chemical Classification System, a system of alphanumeric codes developed by the World Health Organization (WHO) for the classification of drugs and other medical products. Subgroup H03 is part of the anatomical group H Systemic hormonal preparations, excluding sex hormones and insulins.

Codes for veterinary use (ATCvet codes) can be created by placing the letter Q in front of the human ATC code: for example, QH03. National versions of the ATC classification may include additional codes not present in this list, which follows the WHO version.

H03A Thyroid preparations

H03AA Thyroid hormones

H03AA01 Levothyroxine sodium

H03AA02 Liothyronine sodium

H03AA03 Combinations of levothyroxine and liothyronine

H03AA04 Tiratricol

H03AA05 Thyroid gland preparations

H03AA51 Levothyroxine sodium and iodine compounds

H03B Antithyroid preparations

H03BA Thiouracils

H03BA01 Methylthiouracil

H03BA02 Propylthiouracil

H03BA03 Benzylthiouracil

H03BB Sulphur-containing imidazole derivatives

H03BB01 Carbimazole

H03BB02 Thiamazole

H03BB52 Thiamazole, combinations

H03BC Perchlorates

H03BC01 Potassium perchlorate

H03BX Other antithyroid preparations

H03BX01 Diiodotyrosine

H03BX02 Dibromotyrosine

H03C Iodine therapy

H03CA Iodine therapy