Adult IV Maintenance Fluids
4-2-1 base rate plus fever, ongoing-loss, and fluid-restriction adjustments.
- Writing or sanity-checking a maintenance fluid order
- Adjusting maintenance for a febrile patient or one with measurable ongoing losses
- Cross-covering and reconciling a fluid restriction with the rate already running
- Maintenance fluids are usually not what the patient actually needs. Most hospitalized adults are either fluid-restricted or volume-overloaded; routine maintenance is a small fraction of the day-to-day fluid orders.
- For a febrile patient, simply running a fever-adjusted maintenance is rarely sufficient — fever often signals an ongoing process (infection, inflammation) that may need resuscitation, not just maintenance.
- Tonicity matters. Isotonic crystalloid is preferred; chronic 0.45% NaCl + D5W maintenance is a setup for hospital-acquired hyponatremia.
- This tool does not model deficit replacement. If the patient is dehydrated on admission, calculate the deficit separately.
The 4-2-1 number is rarely the right rate to actually run, but it is the right number to anchor the conversation. Showing the base rate, the corrections, and the final number side by side makes the orders defensible and surfaces when a patient is being run on autopilot.
GI, drains, third-space
Final rate
110mL/hr
Per 24 hr
2640mL/day
Maintenance vs resuscitation
This is a maintenance estimate, not a resuscitation rate. For sepsis, hypovolemia, or other shock states, boluses (e.g., 30 mL/kg crystalloid in early sepsis per Surviving Sepsis) take priority and should be titrated to clinical and hemodynamic response, not a maintenance formula.
Frequently asked
What is the 4-2-1 rule for adult IV fluid maintenance?
The 4-2-1 rule estimates hourly maintenance: 4 mL/kg/hr for the first 10 kg of body weight, 2 mL/kg/hr for the next 10 kg, and 1 mL/kg/hr for each kilogram above 20. A 70-kg adult needs about 110 mL/hr. The rule was originally derived from pediatric caloric expenditure (Holliday-Segar 1957) and extrapolates reasonably to healthy adults.
How much do I increase fluids for fever?
Insensible losses rise approximately 12% per °C above 37 (or about 7% per °F above 98.6). For a 70-kg adult on a baseline 110 mL/hr, a temperature of 39 °C adds roughly 26 mL/hr.
What fluid is best for adult maintenance?
Isotonic balanced crystalloid (Lactated Ringer's, Plasma-Lyte) or 0.9% saline is preferred for most hospitalized adults. Hypotonic maintenance fluids (D5 ½ NS, D5 ¼ NS) increase the risk of hospital-acquired hyponatremia and have largely fallen out of favor for general adult inpatients.
When is maintenance fluid the wrong order?
In sepsis, hypovolemia, or hemorrhage, boluses titrated to hemodynamic targets are first-line. In heart failure, advanced cirrhosis, oliguric AKI, or SIADH, fluid restriction may be appropriate. Maintenance fluids are an "average healthy patient" assumption that fits a minority of inpatients well.