Neonatal Glucose Infusion Rate Calculator
Neonatal Glucose Infusion Rate Calculator
Glucose infusion rate in mg/kg/min from the dextrose concentration, the infusion rate and the baby’s weight — the number neonatal teams titrate against, and the one that flags hyperinsulinism when it climbs.
Glucose infusion rate (GIR)
Dextrose % + rate + weight → mg/kg/min10% dextrose running at 15 mL/hour in a 3 kg baby
Formula, and why it is a 6
- dextrose %
- grams per 100 mL. 10% dextrose is 10 g per 100 mL, which is 100 g/L or 100 mg/mL
- the 6
- the whole of the unit conversion, and it is worth deriving once. Grams per hour is (% ÷ 100) × rate. Multiply by 1,000 to get mg/hour and divide by 60 to get mg/min, which is × 1000 ÷ 100 ÷ 60 = ÷ 6. Then divide by weight for mg/kg/min. So GIR = % × rate ÷ 6 ÷ weight — no other constant is hiding in it
- the published check
- UK consensus guidance on congenital hyperinsulinism states that 10% glucose at 5 mL/kg/hour equates to a GIR of 8.3 mg/kg/min. By this formula, 10 × 5 ÷ 6 = 8.33. The defaults on this page reproduce exactly that case
- 4 to 6 mg/kg/min
- the glucose requirement of a newborn baby as UK guidance states it, and the usual starting range for an intravenous infusion
- more than 8 mg/kg/min
- described in UK guidance as excessive and suggestive of hyperinsulinism when it is needed to maintain normoglycaemia. It is a requirement, not a prescription: the number only means this if the baby would otherwise be hypoglycaemic
- 12.5%
- the practical ceiling for peripheral administration. Above it, central venous access is required — a long line or an umbilical venous catheter
- what the formula ignores
- every other source of glucose. Enteral feeds, parenteral nutrition and a second infusion all contribute to total glucose delivery, and this calculation covers one infusion at a time
Worked example
10% dextrose running at 15 mL/hour in a 3 kg baby
15 mL/hour in a 3 kg baby is 5 mL/kg/hour, which is 120 mL/kg/day
GIR = (10 × 15) ÷ (6 × 3) = 150 ÷ 18 = 8.33 mg/kg/min
This is the published check case: UK consensus guidance states that 10% glucose at 5 mL/kg/hour equates to a GIR of 8.3 mg/kg/min, and the formula reproduces it exactly
It is also above the 8 mg/kg/min described as excessive and suggestive of hyperinsulinism — so a baby still hypoglycaemic on this infusion needs the hypoglycaemia screen taken during a low glucose, before it is corrected
Dropping to 10% at 11.25 mL/hour, which is 90 mL/kg/day, gives (10 × 11.25) ÷ 18 = 6.25 mg/kg/min — just above the usual newborn requirement
Going the other way, 12.5% at 12 mL/hour in a 2.5 kg baby gives (12.5 × 12) ÷ 15 = 10.0 mg/kg/min at the peripheral concentration ceiling: any further increase needs central access or a smaller volume at a higher concentration
The same 15 mL/hour of 10% dextrose in a 1 kg preterm baby is (10 × 15) ÷ 6 = 25 mg/kg/min, which is why the weight must be the current one and not an estimate
GIR from common neonatal prescriptions, engine arithmetic
| Fluid | Rate | Weight | GIR (mg/kg/min) |
|---|---|---|---|
| 10% dextrose | 15 mL/hour (5 mL/kg/hour) | 3 kg | 8.33 |
| 10% dextrose | 11.25 mL/hour (90 mL/kg/day) | 3 kg | 6.25 |
| 10% dextrose | 7.5 mL/hour (60 mL/kg/day) | 3 kg | 4.17 |
| 10% dextrose | 5 mL/hour (120 mL/kg/day) | 1 kg | 8.33 |
| 12.5% dextrose | 12 mL/hour | 2.5 kg | 10.00 |
| 15% dextrose | 12 mL/hour | 2.5 kg | 12.00 |
| 5% dextrose | 15 mL/hour | 3 kg | 4.17 |
What the GIR is doing at each level
| GIR (mg/kg/min) | Interpretation |
|---|---|
| Below 4 | Below the usual newborn requirement of 4 to 6 mg/kg/min. Adequate only if feeds or another infusion are contributing |
| 4 to 6 | The usual requirement, and the usual starting range for an infusion |
| 6 to 8 | Above the usual requirement. Common in transitional hypoglycaemia, growth restriction, prematurity and infants of mothers with diabetes |
| Above 8 | Described in UK guidance as excessive and suggestive of hyperinsulinism if it is needed to maintain normoglycaemia. Take the hypoglycaemia screen during a low glucose |
| Above 12 | A high requirement needing explanation, and usually needing central access because the volume at a peripheral concentration becomes limiting |
The practical constraints that shape a GIR
| Constraint | Consequence |
|---|---|
| 12.5% dextrose is the peripheral ceiling | More glucose than that at a tolerable volume means central access — a long line or umbilical venous catheter. Consider it early rather than after the concentration has to rise |
| Fluid allowance | GIR and fluid volume are coupled. At a fixed concentration the only way to raise the GIR is to raise the volume, which is why a baby on restricted fluids needs a higher concentration |
| Extravasation | High-concentration dextrose leaking from a peripheral cannula causes tissue necrosis. The cannula site needs looking at, not just the pump |
| Feeds and parenteral nutrition | Both add glucose. A falling intravenous GIR alongside increasing feeds may mean an unchanged total |
| Abrupt discontinuation | Stopping a high GIR suddenly can cause rebound hypoglycaemia. High rates are weaned, with glucose monitoring, not switched off |
| Sampling method | A handheld glucometer is least accurate at low concentrations, which is exactly where the decision is being made. Confirm a low cot-side reading on a laboratory or blood gas analyser |
The number the cot side actually titrates
Millilitres per hour is what a pump displays and what a prescription says, but it is not a physiological quantity. Fifteen millilitres an hour of ten per cent dextrose delivers a comfortable glucose load to a three-kilogram term baby and a frankly excessive one to a one-kilogram preterm baby, and no amount of staring at the infusion rate reveals that. The glucose infusion rate does: milligrams of glucose per kilogram per minute is the same physiological quantity in both babies, it is the number the published requirements and thresholds are written in, and it is what neonatal teams increase, decrease and record.
The conversion is worth deriving once rather than memorising. A percentage dextrose is grams per hundred millilitres, so ten per cent dextrose is a hundred grams per litre, or a hundred milligrams per millilitre. Multiply by the millilitres per hour to get milligrams per hour, divide by sixty for milligrams per minute, and divide by the weight. Collecting the constants gives the familiar shortcut: the dextrose percentage times the rate in millilitres per hour, divided by six times the weight in kilograms. The six is a thousand divided by a hundred divided by sixty, and nothing else is concealed in it. As a check, UK consensus guidance on congenital hyperinsulinism states that ten per cent glucose at five millilitres per kilogram per hour equates to a rate of 8.3 milligrams per kilogram per minute, and ten times five divided by six is 8.33.
The numbers to hold onto are few. A newborn baby's glucose requirement is generally quoted as four to six milligrams per kilogram per minute, and that is where an intravenous infusion usually starts. Above the usual requirement, a rate of six to eight is common enough in transitional hypoglycaemia, in growth-restricted and preterm babies with poor glycogen stores, and in the infants of mothers with diabetes. Beyond eight, UK guidance is explicit: a rate greater than eight milligrams per kilogram per minute is excessive and suggestive of hyperinsulinism. The essential qualification is that this is a statement about a requirement, not about a prescription. A baby who happens to be receiving a high rate and was never hypoglycaemic tells you nothing; the diagnostic signal is that normoglycaemia cannot be maintained on less, and it is stronger still if the amount needed keeps rising.
When that signal appears, the timing of the investigation matters more than its content. The hypoglycaemia screen — glucose, insulin, C-peptide, ketones, free fatty acids, lactate, ammonia, cortisol, growth hormone, and urine for organic acids — is interpretable only if it is drawn while the glucose is low and before it is corrected. Detectable insulin alongside suppressed ketones and free fatty acids at a low glucose is the hyperinsulinaemic pattern; the same bottles taken an hour after a bolus of dextrose answer nothing and the opportunity has to be recreated deliberately. Two practical constraints then shape what can be done. Concentrations above twelve and a half per cent dextrose require central venous access, so guidance advises considering a long line or umbilical venous catheter early rather than once the concentration has already had to rise. And glucose infusion rate is coupled to fluid volume, so a baby on a restricted fluid allowance can only be given more glucose by making the fluid stronger — which brings the access question back round again.
Frequently asked questions
How do you calculate glucose infusion rate in a neonate?
GIR in mg/kg/min = dextrose percentage × rate in mL/hour ÷ (6 × weight in kg). For 10% dextrose at 15 mL/hour in a 3 kg baby: (10 × 15) ÷ (6 × 3) = 8.33 mg/kg/min. The 6 is the unit conversion — multiply by 1,000 mg/g, divide by 100 mL/dL and by 60 minutes.
What is a normal glucose infusion rate for a newborn?
UK guidance quotes a newborn's glucose requirement as 4 to 6 mg/kg/min, and that is the usual starting range for an intravenous glucose infusion. Rates of 6 to 8 mg/kg/min are common in transitional hypoglycaemia, growth restriction, prematurity and infants of mothers with diabetes.
What GIR suggests hyperinsulinism?
A requirement greater than 8 mg/kg/min to maintain normoglycaemia is described in UK guidance as excessive and suggestive of hyperinsulinism. The key word is requirement: the number is diagnostic only when the baby would be hypoglycaemic on less. Take the hypoglycaemia screen during a low glucose, before it is corrected.
Why does dextrose above 12.5% need central access?
Because of the risk to peripheral veins and the tissue necrosis that follows extravasation of a high-concentration solution. UK guidance advises considering central venous access — a long line or umbilical venous catheter — early, as soon as it looks as though a concentration above 12.5% may be needed.
Do enteral feeds count towards the GIR?
They contribute to total glucose delivery, but this calculation covers one intravenous infusion at a time. A baby whose intravenous GIR is being weaned while feeds increase may have an unchanged total intake, so the intravenous figure alone can be misleading when it is falling for that reason.
Can a high glucose infusion be stopped abruptly?
No. Stopping a high GIR suddenly risks rebound hypoglycaemia, so high rates are weaned with glucose monitoring rather than switched off. This is one reason the GIR is recorded as a number and followed over time rather than being recalculated from scratch at each change.
Related calculators
References
- Paediatric Innovation, Education and Research Network. Initial Assessment and Management of Congenital Hyperinsulinism in Neonates. PIERnetwork guideline — glucose requirement of 4–6 mg/kg/min, GIR above 8 mg/kg/min as excessive and suggestive of hyperinsulinism, and central venous access where glucose concentration above 12.5% is needed.
- Yau D, Salomon-Estebanez M, Chinoy A, et al. Standardised practices in the networked management of congenital hyperinsulinism: a UK national collaborative consensus. Front Endocrinol. 2023;14:1231043 — normal neonatal GIR 4–6 mg/kg/min, rates above 8 mg/kg/min suggesting congenital hyperinsulinism, and the 10% glucose at 5 mL/kg/hour equals 8.3 mg/kg/min worked figure.
- British Association of Perinatal Medicine. Identification and Management of Neonatal Hypoglycaemia in the Full Term Infant: A Framework for Practice. London: BAPM; 2017.
- Thornton PS, Stanley CA, De Leon DD, et al. Recommendations from the Pediatric Endocrine Society for evaluation and management of persistent hypoglycemia in neonates, infants, and children. J Pediatr. 2015;167(2):238–245.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.