Maintenance IV Fluid and Calories

The day's maintenance fluid and calories, the electrolytes in it, and the losses on top · v1.3

Enter the biometrics, the clinical phenotype, the current serum electrolytes and the ongoing losses.
You get the daily requirement for water, sodium, potassium and obligatory glucose, set against this patient's own biochemistry.
It then names a fluid and a rate that meet that requirement, with the potassium to add to it.
Read the glucose figure as anti-ketosis cover, not as feeding. It is not a nutrition calculation: 50 to 100 g a day keeps a fasting patient out of starvation ketosis and does nothing more.

Children. Every requirement here is derived for adults.
Resuscitation. This is maintenance: it computes no bolus, and it does not replace an established deficit in shock or dehydration.
A daily energy target or a protein target, both of which depend on the illness, the catabolic state and the route. A patient who will not be eating within about 48 hours needs the dietitian or the nutrition team.
Parenteral and enteral feed prescriptions, and the correction of an electrolyte disturbance already established, which the electrolyte modules carry.

1. Patient Baseline

Age (yrs) Completed years. Adults 18+ only. Paediatric dosing uses the Holliday-Segar formula (separate tool).

Biological Sex Required for Ideal Body Weight calculation (Devine formula). IBW differs by ~4.5 kg between sexes at the same height.

Male Female

Height (cm) Standing height in centimetres. Used alongside sex to calculate IBW and BMI. For bedridden patients, use arm span or ulna length estimate.

Actual Body Weight (kg) Current weight in kg. For BMI > 30, the tool automatically uses Adjusted Body Weight (ABW) to prevent fluid overload from adipose tissue overestimation.

2. Clinical Phenotype

Fluid Restriction Profile Standard: 30 mL/kg/day. Elderly/Frail: 25 mL/kg/day (reduced cardiac reserve). HF/CKD: 20 mL/kg/day (strict restriction). Oliguric: insensible + measured losses only.

3. Current Serum Electrolytes (Strongly Recommended)

Clinical Safety: Enter the sodium and the potassium if you have them. They decide which fluid and which additive is safe, and nothing else on this form can substitute for them. If the labs are still pending, the tool gives an empiric estimate and says on the result exactly where it is estimating.

Serum Na+ (mmol/L) Normal: 135 to 145 mmol/L. This value decides the tonicity of the fluid. A hypotonic fluid (0.45% NS) given in hyponatraemia can cause fatal cerebral oedema.

Serum K+ (mmol/L) Normal: 3.5 to 5.0 mmol/L. NEVER add KCl to IV fluids without a documented serum K+. Empiric K+ in a hyperkalaemic patient can cause fatal arrhythmia.

4. Dynamic & Insensible Losses

Max Core Temperature (°F) Highest recorded temperature in past 24 hours, in Fahrenheit. Normal: 98.6°F. Each degree above 98.6°F adds ~55 mL/day insensible loss (each °C above 37 adds ~100 mL). Range: 95 to 107°F.

Tachypnoea / Diaphoresis Extra insensible water lost through rapid breathing, profuse sweating, or open abdominal wounds. These losses are invisible and unmeasurable at the bedside.

Measurable Losses (Drains/NG in mL/day) Total 24-hour output from surgical drains, nasogastric tubes, fistulae, or ostomy bags. Do NOT include urine output here (UO is already accounted for in the basal calculation).

The 0.9% Saline Error

Common Clinical Oversight: "Normal Saline @ 100 mL/hr", written without thinking, delivers 2.4 Litres a day carrying 369 mmol of Sodium and Chloride. The daily requirement is about 70 mmol. Everything above that is a salt load the patient has no use for, and it buys you Hyperchloraemic Metabolic Acidosis, vasoconstriction of the renal efferent arteriole, interstitial oedema, and a longer stay.

1. Comparative IV Fluid Composition

Choose the fluid by what is in the bag, not by what it is called. (Values approximate, per Litre.)

Fluid Type	Na+ (mmol)	Cl- (mmol)	K+ (mmol)	Buffer / Other	Calories / Osmolarity
0.9% Normal Saline	154	154	0	None	0 kcal / 308 mOsm/L
Ringer's Lactate	130	109	4	Lactate 28, Ca 1.4	0 kcal / 273 mOsm/L
Plasma-Lyte 148	140	98	5	Acetate 27, Gluconate 23, Mg 1.5	0 kcal / 294 mOsm/L
0.45% Saline + 5% Dextrose	77	77	0	Dextrose 50 g	200 kcal / 406 mOsm/L
Isolyte-P in 5% Dextrose	23	29	20	Acetate 23, Mg 1.5, Phosphate 1.5, Dextrose 50 g	170 kcal / 340 mOsm/L
5% Dextrose (D5W)	0	0	0	Dextrose 50 g	200 kcal / 252 mOsm/L
5% Dextrose in 0.9% NS (DNS)	154	154	0	Dextrose 50 g	200 kcal / 560 mOsm/L

2. Starvation Ketosis, Dextrose, and What This Tool Does Not Give You

A patient kept NPO beyond 12 hours needs obligatory glucose, to suppress lipolysis and stop the breakdown of protein. The pure crystalloids carry none of it.

The minimum is 50 to 100 grams of Dextrose per day, which is 200 to 400 kcal (NICE CG174, 2013).
NS, RL and Plasmalyte are all zero calories, so a standard maintenance prescription has to carry a Dextrose-containing fluid with it, and 0.45% Saline + 5% Dextrose is the usual one.
A litre of 5% Dextrose gives 50 grams of glucose, or 200 kcal. Two litres cover the obligatory minimum.

200 to 400 kcal a day is not feeding anybody. It is enough to stop ketosis and no more, and a resting adult needs several times that. This tool stops at the obligatory glucose on purpose: it does not calculate a daily energy target and it does not calculate a protein target, because both depend on the illness, the catabolic state and the route, and neither belongs inside a maintenance fluid prescription. If the patient will not be eating within about 48 hours, that is the point to involve the dietitian or the nutrition team and to plan enteral feeding, rather than to add dextrose bags.

3. Potassium in Maintenance Fluids

The kidney obligatorily excretes potassium even in hypokalaemic states.

Daily maintenance requires roughly 1 mmol/kg/day, typically 40 to 80 mmol/day, capped at 80 mmol for routine maintenance.
Adding 20 mmol KCl per litre is the standard safe concentration for peripheral IV infusion. At typical maintenance volumes of 2 to 2.5 L this provides 40 to 50 mmol, which may not fully meet the daily requirement. Cover the shortfall with oral supplements or additional IV KCl if the patient remains NPO.
Safety rule. NEVER add KCl to IV fluids without a documented serum K+ value and confirmed urine output (> 0.5 mL/kg/hr). Do not add potassium if serum K+ is above 5.0 mmol/L. If K+ is above 5.5, treat the hyperkalaemia first.

4. Serum Sodium and Fluid Tonicity

The choice between a hypotonic (0.45% NS) and an isotonic (0.9% NS) maintenance fluid is made on the serum sodium, and this synthesiser adjusts its recommendation on the value entered.

Hyponatraemia, Na+ < 130. Giving hypotonic fluid worsens the dilutional state and can cause fatal cerebral oedema. These patients need isotonic fluids or fluid restriction, depending on the cause.
Hypernatraemia, Na+ > 145. The patient needs free water, D5W or 0.45% NS, to correct the deficit.

5. Obesity and Fluid Dosing

Adipose tissue needs less water per kilogram than lean mass does. Dose an obese patient (BMI > 30) on actual body weight and the requirement comes out dangerously high. Use Adjusted Body Weight instead: ABW = IBW + 0.4 × (Actual Weight - IBW). Above a BMI of 30 this tool makes that substitution for you and says so on the result.

6. Why Not Ringer's Lactate for Maintenance?

RL is an excellent resuscitation fluid but a poor maintenance fluid.

It contains 130 mmol/L Na+, against a daily need of only about 1 mmol/kg.
It provides zero calories, so the starvation ketosis risk is not covered.
It contains calcium, which is incompatible with blood products and with certain drugs in the same IV line.

For maintenance, hypotonic dextrose-saline combinations are preferred.

7. Temperature: Fahrenheit and Celsius at the Indian Bedside

Most clinical thermometers in Indian hospitals display in Fahrenheit. Normal body temperature is 98.6°F (37°C) and the fever threshold for fluid adjustment is 100.4°F (38°C). This tool accepts temperature in Fahrenheit, converts internally, and validates the range at 95 to 107°F, because entering a Celsius-ranged number in a Fahrenheit field, or the reverse, is a recurring entry error.

Abbreviations: ABW (Adjusted Body Weight) · BMI (Body Mass Index) · Ca (Calcium) · CKD (Chronic Kidney Disease) · Cl⁻ (Chloride) · CSW (Cerebral Salt Wasting) · D5W (5% Dextrose in Water) · DNS (Dextrose Normal Saline) · ECG (Electrocardiogram) · ESRD (End-Stage Renal Disease) · HF (Heart Failure) · IBW (Ideal Body Weight) · IV (Intravenous) · K⁺ (Potassium) · KCl (Potassium Chloride) · Mg²⁺ (Magnesium) · Na⁺ (Sodium) · NaCl (Sodium Chloride) · NG (Nasogastric) · NPO (Nil Per Os) · NS (Normal Saline) · RL (Ringer's Lactate) · SBAR (Situation, Background, Assessment, Recommendation) · SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion) · UO (Urine Output)

References

National Institute for Health and Care Excellence (NICE). Intravenous fluid therapy in adults in hospital (CG174). London: NICE; 2013 (Updated 2017).
Indian Council of Medical Research (ICMR). Standard Treatment Workflows (STW) for Common Conditions. New Delhi.
Association of Physicians of India (API). API Textbook of Medicine. Fluid and Electrolyte Balance.
Myburgh JA, Mythen MG. Resuscitation fluids. N Engl J Med. 2013;369(13):1243-1251.
Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650-655.
Lobo DN et al. Problems with solutions: drowning in the brine of an inadequate knowledge base. Clin Nutr. 2001;20(2):125-130.
Padhi S, Bullock I, Li L, Stroud M. Intravenous fluid therapy for adults in hospital: summary of NICE guidance. BMJ. 2013;347:f7073.

How to Cite This Tool

DOIhttps://doi.org/10.5281/zenodo.22401608

AMA Style:Umakanth S. Maintenance IV Fluid and Calories. Version 1.3. MEDiscuss Clinical Decision Support System. Published 2026. Accessed . https://mediscuss.org/cdss/iv-fluid-caloric-synthesiser. doi:10.5281/zenodo.22401608

Vancouver Style:Umakanth S. Maintenance IV Fluid and Calories [Internet]. Version 1.3. MEDiscuss.org; 2026 [cited ]. Available from: https://mediscuss.org/cdss/iv-fluid-caloric-synthesiser. doi:10.5281/zenodo.22401608

Category Therapeutic & Management PathwaysCalculator

Specialties Internal Medicine, Critical Care

Written and maintained by

Dr Shashikiran Umakanth

Last revised 24 August 2026

How these tools are written and reviewed