- Guertin's disease (electric chorea) 049.8
- Guillain-Barré disease or syndrome 357.0
- Guinea worms (infection) (infestation) 125.7
- Guinon's disease (motor-verbal tic) 307.23
- Gull and Sutton's disease - see Hypertension, kidney
- Gull's disease (thyroid atrophy with myxedema) 244.8
- Gum - see condition
- Gumboil 522.7
- Gumma (syphilitic) 095.9
- Gunn's syndrome (jaw-winking syndrome) 742.8
- Gunshot wound - see also Wound, open, by site
- Günther's disease or syndrome (congenital erythropoietic porphyria) 277.1
- Gustatory hallucination 780.1
- Gynandrism 752.7
- Gynandroblastoma (M8632/1)
- Gynandromorphism 752.7
- Gynatresia (congenital) 752.49
- Gynecoid pelvis, male 738.6
- Gynecological examination V72.31
- Gynecomastia 611.1
- Gynephobia 300.29
- Gyrate scalp 757.39