- Hippel's disease (retinocerebral angiomatosis) 759.6
 - Hippus 379.49
 - Hirschfeld's disease (acute diabetes mellitus) (see also Diabetes) 250.0
 - Hirschsprung's disease or megacolon (congenital) 751.3
 - Hirsuties (see also Hypertrichosis) 704.1
 - Hirsutism (see also Hypertrichosis) 704.1
 - Hirudiniasis (external) (internal) 134.2
 - His-Werner disease (trench fever) 083.1
 - Hiss-Russell dysentery 004.1
 - Histamine cephalgia 339.00
 - Histidinemia 270.5
 - Histidinuria 270.5
 - Histiocytic syndromes 288.4
 - Histiocytoma (M8832/0) -  see also Neoplasm, skin, benign
 - Histiocytosis (acute) (chronic) (subacute) 277.89
 - Histoplasmosis 115.90
 - History (personal) of
 - HIT (heparin-induced thrombocytopenia) 289.84
 - HIV infection (disease) (illness) - see Human immunodeficiency virus (disease) (illness) (infection)
 - Hives (bold) (see also Urticaria) 708.9
 - Hoarseness V87.46
 - Hobnail liver - see Cirrhosis, portal