From Wikipedia, the free encyclopedia
In medicine, guttae, the plural of gutta, is Latin for drops. It is frequently abbreviated as gtts (gtt for singular) and often seen on prescriptions. Other sources abbreviate gt for singular, and gtt for plural. 
- McGarry RC, McGarry P (1999). "Please pass the strychnine: the art of Victorian pharmacy". Canadian Medical Association Journal. 161 (12): 1556–8. PMC . PMID 10624415.