Clinical benefits and safety of carbohydrate loading pre-gastroscopy remain unclear. We aimed to determine the effects of a commercial carbohydrate-rich whey protein beverage versus plain water given pre-gastroscopy on gastric residual volume and well-being, and to determine adverse events. This was a single centre, single-blinded, parallel-group, sex-stratified randomized controlled trial. Participants were randomized either to carbohydrate-rich whey protein beverage group (Resource®, Nestle Health Science) or control group (250 ml plain water) given pre-gastroscopy. Gastric contents were aspirated into a suction reservoir bottle to determine the gastric residual volume (GRV). Visual analogue scale (VAS) of well-being (anxiety, hunger, thirst, tiredness, and weakness) was compared before and after the intervention. Adverse events were also evaluated post-intervention. Of 369 screened, 78 participants (36 males, mean age 49 ± 14.3 years) were randomized. Compared with the control group, carbohydrate beverage was associated with significantly higher GRV (p