Gastric Emptying Time for Water
Water has a gastric emptying half-life of approximately 15 minutes, meaning a glass of water will be almost completely emptied from the stomach within 30-60 minutes. 1
Gastric Emptying Physiology for Liquids
Water empties from the stomach following first-order kinetics (exponential decline), unlike solids which follow zero-order kinetics (constant rate). This has important implications for understanding how quickly water passes through the stomach:
- Water empties faster than any other substance, with a half-life of approximately 15 minutes 1
- With this half-life, even a 200 ml drink of water would be reduced to:
- 50 ml after 15 minutes
- 25 ml after 30 minutes
- Less than 12.5 ml after 45 minutes 1
Factors Affecting Gastric Emptying of Water
Several factors can influence how quickly water empties from the stomach:
- Volume: Larger volumes initially empty faster, but very large volumes (>7 ml/kg) may not completely empty within 1 hour 1
- Temperature: Cold water (5°C) empties significantly faster than room temperature water (20-25°C) or warm water (45°C) 2
- Mixing with other substances: Water consumed separately empties much faster than when blended with nutrients 3
- Individual variation: There is considerable inter-individual variation in gastric emptying rates 1
Clinical Implications
The rapid emptying of water has important clinical implications:
- For preoperative fasting, guidelines suggest that a 1-hour fasting time for water is entirely reasonable 1
- This is why many anesthesia guidelines now allow clear fluids up to 2 hours before surgery, with some even considering shorter intervals 1
- When water is consumed with medications, cold water may help medications pass through the stomach more quickly 2
Common Pitfalls to Avoid
- Assuming all liquids empty at the same rate: Unlike water, caloric beverages empty much slower (tea with milk has a half-life of about 25 minutes) 1
- Confusing water with other clear fluids: While water empties quickly, other clear fluids containing calories (like apple juice) will empty more slowly 1, 4
- Not accounting for pathological conditions: Conditions like gastroparesis, gastroesophageal reflux disease, and diabetes can significantly delay gastric emptying 5, 6
In summary, water empties from the stomach quite rapidly with a half-life of approximately 15 minutes, making it almost completely cleared within an hour under normal physiological conditions.