- Greig's syndrome (hypertelorism) 756.0
- Griesinger's disease (see also Ancylostomiasis) 126.9
- Grinders'
- Grinding, teeth 306.8
- Grip
- Grippe, grippal - see also Influenza
- Grippy cold 487.1
- Grisel's disease 723.5
- Groin - see condition
- Grooved
- Ground itch 126.9
- Growing pains, children 781.99
- Growth (fungoid) (neoplastic) (new) (M8000/1) - see also Neoplasm, by site, unspecified nature
- GRSA (glycopeptide resistant staphylococcus aureus) V09.8
- Gruber's hernia - see Hernia, Gruber's
- Gruby's disease (tinea tonsurans) 110.0
- Guama fever 066.3
- Gubler (-Millard) paralysis or syndrome 344.89
- Guérin-Stern syndrome (arthrogryposis multiplex congenita) 754.89
- Guertin's disease (electric chorea) 049.8
- Guillain-Barré disease or syndrome 357.0
- Guinea worms (infection) (infestation) 125.7
