Drinking an extra 1.5 liters of water each day for six weeks lowers fasting blood glucose levels in people who are moderately dehydrated.
See the scientific wording
Increasing daily water intake by 1.5 liters for six weeks reduces fasting plasma glucose in moderately dehydrated individuals.
Very strong evidence
Randomized trialsOne moderate-quality study supports this claim, so treat this as an early signal rather than settled science.
What the research says
1 study reviewedSupporting (1)
Randomized Controlled TrialHuman2021
People who didn't drink enough water and were mildly dehydrated saw their fasting blood sugar go down after they started drinking an extra 1.5 liters of water every day for six weeks. So yes, drinking more water helped lower their blood sugar.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
Scores reflect study quality, not just count.
Drinking more water lowers the body's stress hormone signal, which tells the liver to stop making so much sugar, leading to lower blood sugar levels in the morning.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting study
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Drinking an extra 1.5 liters of water each day for six weeks lowers fasting blood glucose levels in people who are moderately dehydrated.
Mechanism
1 studyDrinking more water tells the brain to stop signaling stress, which lowers cortisol. Lower cortisol means the liver stops making extra sugar, so morning blood sugar drops.
Drinking more water lowers the body's stress hormone signal, which tells the liver to stop making so much sugar, leading to lower blood sugar levels in the morning.
Increased water intake lowers plasma osmolality, reducing stimulation of hypothalamic osmoreceptors
Reduced osmoreceptor signaling decreases vasopressin secretion from the hypothalamus
Lower vasopressin levels reduce activation of V1b receptors on anterior pituitary corticotrophs
Reduced V1b receptor activation decreases adrenocorticotropic hormone (ACTH) release from the pituitary
Lower ACTH levels reduce cortisol production by the adrenal glands
Reduced cortisol levels decrease gluconeogenesis and hepatic glucose production
Lower hepatic glucose output reduces fasting plasma glucose concentration
Evidence from Studies
Last searched 3mo ago
Supporting (1)
Community contributions welcome
Investigation of possible underlying mechanisms behind water-induced glucose reduction in adults with high copeptin
People who didn't drink enough water and were mildly dehydrated saw their fasting blood sugar go down after they started drinking an extra 1.5 liters of water every day for six weeks. So yes, drinking more water helped lower their blood sugar.
Contradicting (0)
Community contributions welcome
Score Breakdown
No multi-axis breakdown available yet. The overall Pro / Against score above is the best signal.
- No clinical evidence is available; the score reflects mechanistic plausibility only.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Systematic Review of Water Intake Interventions on Fasting Plasma Glucose in Moderately Dehydrated Adults
Population: Moderately dehydrated adults; Intervention: Increased daily water intake by 1.5 liters; Comparator: Stable water intake; Outcome: Change in fasting plasma glucose; Duration: Six weeks.
Double-Blind Placebo-Controlled Trial of 1.5 L/day Water Increase on Fasting Glucose in Moderately Dehydrated Adults
Population: Moderately dehydrated adults; Intervention: 1.5 liters additional water per day; Comparator: Placebo (no change in water intake); Outcome: Fasting plasma glucose measured at baseline and week 6; Duration: Six weeks; Design: Randomized, double-blind, parallel-group.
Prospective Cohort Study of Water Intake and Fasting Glucose Changes in Moderately Dehydrated Adults Over Six Weeks
Population: Moderately dehydrated adults; Exposure: Self-reported increase of 1.5 liters daily water intake; Comparator: Stable water intake group; Outcome: Fasting plasma glucose measured at baseline and week 6; Duration: Six weeks; Design: Prospective, non-randomized.
Cross-Sectional Analysis of Water Intake and Fasting Glucose Levels in Moderately Dehydrated Adults
Population: Moderately dehydrated adults; Exposure: Current daily water intake; Outcome: Single measurement of fasting plasma glucose; Duration: Single time point; Design: Observational, no intervention.
In Vitro Effects of Hypotonic Fluid Exposure on Hepatocyte Glucose Release
Population: Human hepatocyte cell lines; Intervention: Exposure to hypotonic solution mimicking increased hydration; Comparator: Isotonic solution; Outcome: Glucose release rate; Duration: 24–72 hours; Design: Controlled laboratory environment.