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Hydration target calculator.

A starting point for daily fluid intake across the bariatric journey, GLP-1 therapy, and long-term metabolic health. Built on ASMBS post-op hydration guidance and standard baseline-fluid math, with adjustments for activity, climate, post-op stage, and GLP-1-related appetite reduction.

Educational tool, not medical advice. This estimates a starting daily fluid range from published guidelines. It does not replace personalised advice from your bariatric team, dietitian, or prescriber. If you have heart failure, kidney disease, or fluid restrictions, follow the personalised target your clinical team has given you. Call your local emergency number for urgent symptoms including signs of severe dehydration.

Your details

Used to scale a baseline fluid target.
Sets post-op sip-schedule guidance.
Earlier stages require slower sipping over more hours.
Adds fluid for sweat losses.
Hot / very dry air increases fluid losses.
GLP-1 medications and early post-op suppress thirst signals — you may need a reminder schedule.

Your daily fluid target

Daily target
—
fl oz/day
Equivalent
—
mL/day
Sip target
—
fl oz / 15 min
How to read this:

    Post-op sipping rules

      How this works

      • Baseline: roughly 64 fl oz/day (about 1.9 L) as a non-surgical adult floor, scaled up for body weight (about 0.5 fl oz per pound, or 30–35 mL per kg).
      • Post-op floor: ASMBS guidance recommends at least 48–64 fl oz/day (about 1.4–1.9 L) for bariatric post-op clients, spread across the day in small sips.
      • Activity: adds 8–24 fl oz for light through high activity to replace sweat losses.
      • Climate: hot or very dry environments add up to 16 fl oz; cold dry indoor heat adds about 8 fl oz to offset insensible losses.
      • Sip target: divides the daily fluid target across waking hours (assumed 14 hours) in 15-minute increments to support post-op pacing.
      • GLP-1 / reduced appetite: does not change the target, but adds a structured-reminder note, because GLP-1 medications often suppress thirst.

      Sources

      American Society for Metabolic & Bariatric Surgery (ASMBS) Integrated Health Nutritional Guidelines — ASMBS Clinical Practice Guidelines

      Obesity Canada Clinical Practice Guidelines — obesitycanada.ca/guidelines

      Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press, 2005 (general adult fluid baseline).

      Want personalised guidance?

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