GLP-1 water intake calculator
Work out your daily water target, adjusted for GLP-1 thirst changes, GI side effects and clinical guidelines.
Adapted from EFSA and ESPEN fluid guidance
The estimate starts from a total water need of 35 mL per kg a day (30 mL/kg from age 65), a common clinical rule. Only a quarter of any weight above 70 kg (men) or 60 kg (women) is counted, because body fat holds much less water than muscle. Your drinks are 85% of that total, a little above the 70–80% ESPEN describes, because eating less on a GLP-1 means less water from food. Typical amounts are then added for activity, heat and digestive side effects. The result never falls below 2.0 L (men) or 1.75 L (women) of drinks, at or above the minimums based on EFSA’s reference intakes, and never goes above 4.0 L.
Not medical advice
This calculator provides general guidance based on published clinical standards and consensus guidelines. It does not replace personalized advice from your healthcare provider. Fluid needs vary based on individual health conditions, kidney function, and other factors. Always consult your doctor.
What this calculator targets
GLP-1s slow gastric emptying and reduce both food and fluid intake. Most users need slightly more water than baseline because they get less water from food, and dehydration drives the two most common GLP-1 complaints: constipation and nausea. This calculator gives you a daily target based on body weight, activity level, and climate.
Who is this for?
Anyone on a GLP-1, especially during the first 8 weeks and at every dose increase. If you struggle with constipation, fatigue, headaches, or muscle cramps on your medication, dehydration is often the first place to look.
Frequently asked questions
How much water should I drink on Ozempic?
For most adults on a GLP-1, a realistic goal is about 2–3 L (70–100 fl oz) of drinks a day, counting water, tea, milk and soups, with more on active, hot or sick days. Eating less also means less water from food.
Why am I constipated on Ozempic?
GLP-1s slow gastric emptying and reduce both food and fluid intake. Low water and low fiber are the two biggest constipation drivers.
Does electrolyte water help on a GLP-1?
Yes. Sodium, potassium, and magnesium can ease cramping, fatigue, and constipation, especially during dose escalations.
Can I drink coffee on a GLP-1?
Yes, but coffee can worsen reflux and nausea on GLP-1s. Count coffee toward fluid totals only if it does not trigger symptoms.
Related reading
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