Calculates the NICE adult routine maintenance water range of 25–30 mL/kg/day. This premium guide explains physiology, calculation, interpretation, limitations and evidence.
Overview
Calculates the NICE adult routine maintenance water range of 25–30 mL/kg/day.
Clinical Significance
A starting range for routine adult maintenance only; frailty, cardiac failure, renal impairment and malnutrition may require less.
When to Use
- Estimate initial routine maintenance water needs.
- Use within a complete fluid plan.
- Review status and losses daily.
How It Is Calculated
- Routine maintenance water = 25–30 mL/kg/day.
- MedicalC validates required values and rounds only the displayed result.
Interpretation
- A starting range for routine adult maintenance only; frailty, cardiac failure, renal impairment and malnutrition may require less.
- Review source measurements, collection quality and clinical trajectory as well as the final value.
Worked Example
Enter clinically plausible values in the displayed units. MedicalC applies: Routine maintenance water = 25–30 mL/kg/day. Verify the result against the source data before use.
Patient Considerations
- Consider kidney function, diuretics, intravenous fluids, nutrition, body composition and rapidly changing physiology.
- For timed urine calculations, confirm collection duration, volume and completeness.
- For electrolyte prescriptions, include all oral, enteral, intravenous and medication sources.
Limitations
- Not for resuscitation or abnormal-loss replacement.
- Obesity and oedema require careful weight selection.
- Comorbidity may require lower volumes.
Clinical Pearls
- Use paired serum and urine values obtained as close together as possible when the formula requires them.
- A derived renal index is only as reliable as the collection and assays used.
- Check whether treatment occurred between sampling and interpretation.
Common Mistakes
- Mixing µmol/L and mmol/L creatinine values.
- Using spot concentrations as daily excretion rates.
- Ignoring incomplete timed urine collection.
- Treating a maintenance estimate as a replacement or emergency-correction regimen.
- Using a derived acid–base value without checking albumin, lactate and the blood gas.
Evidence Base
Principal source: NICE CG174. Intravenous fluid therapy in adults in hospital.
Frequently Asked Questions
What does the Adult Routine Maintenance Water Requirement calculator do?
Calculates the NICE adult routine maintenance water range of 25–30 mL/kg/day.
Can this result establish a diagnosis?
No. It is an adjunct that must be combined with clinical assessment and current guidance.
Why are timing and units important?
Derived results can be misleading when values are non-contemporaneous or use incompatible units.
When should the calculation be repeated?
Repeat when treatment, kidney function or the relevant measured values change and a new result could influence care.
Does this replace a specialist protocol?
No. Direct measurement, laboratory interpretation and specialist protocols take priority.
References
- NICE CG174. Intravenous fluid therapy in adults in hospital. — Primary publication, guideline or authoritative specialty source.
Reviewed by: MedicalC Clinical Editorial Team
Last reviewed: July 2026