- Floater, vitreous 379.24
- Floating
- Flooding 626.2
- Floor - see condition
- Floppy
- Flu - see also Influenza
- Fluctuating blood pressure 796.4
- Fluid
- Flukes NEC (see also Infestation, fluke) 121.9
- Fluor (albus) (vaginalis) 623.5
- Fluorosis (dental) (chronic) 520.3
- Flush syndrome 259.2
- Flushing 782.62
- Flutter
- Flux (bloody) (serosanguineous) 009.0
- FNHTR (febrile nonhemolytic transfusion reaction) 780.66
- Focal - see condition
- Fochier's abscess - see Abscess, by site
- Focus, Assmann's (see also Tuberculosis) 011.0
- Fogo selvagem 694.4
- Foix-Alajouanine syndrome 336.1
- Folds, anomalous - see also Anomaly, specified type NEC