Free tool · no signup
Water intake calculator
See how much fluid adults typically need each day, based on published reference intakes, with an allowance for exercise and hot weather.
GLPMate logs water alongside doses and side effects, so you can see what helps on rough days.
The US National Academies set an adequate intake of about 3.7 L of total water a day for men and 2.7 L for women; the European Food Safety Authority (EFSA) sets 2.5 L and 2.0 L. Both include water from food, which supplies roughly 20%, so most of it comes from drinks. Exercise and heat add to that. On a GLP-1, vomiting or diarrhea can dehydrate you quickly.
Where the numbers come from
The starting point is an adequate intake (AI) of total water: the amount healthy adults typically drink and eat without signs of dehydration. It covers water from all drinks and food, in temperate conditions with moderate activity.
| Reference | Women | Men |
|---|---|---|
| US National Academies | 2.7 L | 3.7 L |
| EFSA (Europe) | 2.0 L | 2.5 L |
Exercise and heat
For exercise, this calculator adds 0.4 L per hour, or 0.8 L per hour in hot weather — the two ends of the 0.4–0.8 L per hour starting range in the American College of Sports Medicine's fluid-replacement guidance. Sweat rates vary a lot from person to person, so treat this as a starting point.
Is it a target?
No. Adequate intakes are population averages, not personal requirements. Thirst, how often you pass urine and its colour are practical everyday checks. Older adults may feel less thirsty, so drinking steadily matters more.
This calculator is for general education only. It is not medical advice. If you have heart, kidney or liver disease, or have been told to limit fluids, follow your clinician’s advice on how much to drink.
Sources
- US National Academies — Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005) — adequate intake of total water: 3.7 L/day for men, 2.7 L/day for women; about 20% comes from food
- EFSA — Scientific Opinion on Dietary Reference Values for water (2010) — adequate intake of total water: 2.5 L/day for men, 2.0 L/day for women
- American College of Sports Medicine — Exercise and Fluid Replacement position stand (2007) — 0.4–0.8 L per hour as a starting range during exercise
- FDA prescribing information for Wegovy and Zepbound (Wegovy, Zepbound) — warning on acute kidney injury linked to dehydration from gastrointestinal side effects
Last updated:
Hydration questions
How much water should I drink a day?
Reference intakes for total water are about 2.7 L a day for women and 3.7 L for men (US National Academies), or 2.0 L and 2.5 L (EFSA). Around 20% usually comes from food, so drinks make up the rest. Needs rise with exercise and heat.
Do GLP-1 medications cause dehydration?
They can contribute to it. Nausea, vomiting and diarrhea are common side effects, especially when starting or increasing the dose, and eating less can also mean less water from food. The labels warn about acute kidney injury linked to dehydration from these side effects.
Do coffee and tea count?
Yes. All drinks count toward total water, and so does the water in food. Caffeinated drinks have a mild diuretic effect but still add to your intake overall.
When should I call my doctor?
Contact your prescriber or seek care if you can't keep fluids down, have vomiting or diarrhea that doesn't settle, feel dizzy or faint, or pass very little urine. If you have been told to restrict fluids, follow that advice.
Log water with one tap.
Track water alongside doses and side effects in GLPMate. iOS & Android.