- failure to thrive: FTT
- family history: FH
- Farenheit: F or F.
- fasting blood sugar: FSB
- Fellow, American College of Physicians: FACP
- Fellow, American College of Surgeons: FACS
- fetal heart tones: FHT
- fever of unknown/undetermined origin: FUO
- flourescent treponemal antibody: FTA
- follicle-stimulating hormone: FSH
- follow-up: F/U
- Food and Drug Administration: FDA
- forced expiratory flow: FEF
- forced expiratory volume: FEV
- forced vital capacity: FVC
- foreign body; fingerbreadth: FB
- fractional urine: fx urine
- fracture: Fx
- full range of motion/movement: FROM
- iron: Fe