| FER | flexion, extension, rotation; fractional esterification rate |
|---|---|
| FFWC | fractional free water clearance |
| FIC | Fogarty International Center; fractional inhibitory concentration |
| FiCO2, | FICO2 fractional concentration of carbon dioxide in inspired gas |
| FIO2 | forced inspiratory oxygen; fractional concentration of oxygen in inspired gas |