Clear liquids
Clear liquids has been studied in 1 paper since 2025: 1 trial in people. The newest paper, Jul 2, 2025: “The safety and effect of preoperative reduced fasting time by oral clear liquid administration in adult surgery patients: a randomized controlled trial”.
1 paper studies it3 findingsUpdated
“Pre- and postoperative thirst and hunger scores were significantly lower in the liquid group (P < 0.001).”
None of its findings points the other way.
- 1 lab in 1 country
- Human trial1
What did studies of Clear liquids find?
3Studies of Clear liquids measured 3 outcomes; the most studied are gastric content volume (1 study), hunger (1) and thirst (1).
Gastric content volume
no changein humans1
1 study
Gastric content volume
no changein humans1
Clear liquids have no effect on gastric content volume in humans (<1 mL).
“Gastric content volume and acidity showed no significant differences between groups, with most patients having negligible volumes (<1 mL).”
Human trialoral clear liquiduntil 2 hours before surgeryn = 60
Annals of surgical treatment and research
Hunger
downin humans1
1 study
Hunger
downin humans1
Clear liquids decrease hunger in humans (P < 0.001).
“Pre- and postoperative thirst and hunger scores were significantly lower in the liquid group (P < 0.001).”
Human trialoral clear liquiduntil 2 hours before surgeryn = 60
Annals of surgical treatment and research
THIRST
downin humans1
1 study
THIRST
downin humans1
Clear liquids decrease thirst in humans (P < 0.001).
“Pre- and postoperative thirst and hunger scores were significantly lower in the liquid group (P < 0.001).”
Human trialoral clear liquiduntil 2 hours before surgeryn = 60
Annals of surgical treatment and research