Why GIR matters in newborns
Before birth, a baby receives a continuous supply of glucose through the placenta. After the cord is cut, the newborn must make its own glucose and feed regularly. Premature babies, small or sick newborns and infants of diabetic mothers often cannot, and they receive glucose by infusion. Neonatal teams prescribe it as a glucose infusion rate (GIR), in milligrams of glucose per kilogram of body weight per minute, because that matches the baby’s metabolic needs regardless of the fluid volume.
The formula
GIR (mg/kg/min) = dextrose % × infusion rate (mL/h) ÷ (6 × weight in kg)
The factor 6 comes from the unit conversions: a 10% solution contains 100 mg of glucose per mL, and there are 60 minutes in an hour.
Turned around:
- Rate for a target GIR = GIR × 6 × weight ÷ dextrose %
- Concentration for a target GIR = GIR × 6 × weight ÷ rate
Worked example
A 3 kg baby receives 10% dextrose at 10 mL/h:
- GIR = 10 × 10 ÷ (6 × 3) = 5.56 mg/kg/min.
- Daily fluid: 10 × 24 ÷ 3 = 80 mL/kg/day.
- Glucose delivered: about 24 g a day.
- To reach a GIR of 6, the rate would be 10.8 mL/h, or the concentration 10.8% at the current rate.
Typical values
- A term newborn’s liver produces about 4 to 6 mg/kg/min of glucose, so infusions often start in that range.
- Premature babies frequently need 6 to 8 mg/kg/min.
- Needs above about 12 mg/kg/min are unusual and prompt a search for a cause, such as hyperinsulinism.
The team adjusts the GIR to repeated blood glucose checks, and reduces it gradually as feeds are increased.
Practical limits
- Concentration: solutions above about 12.5% dextrose irritate peripheral veins and usually need a central line, such as an umbilical or peripherally inserted central catheter.
- Fluid volume: newborns can only tolerate a certain volume per kilogram per day, which rises over the first days of life. To give more glucose without more fluid, the concentration must rise.
- Total GIR: if the baby receives several glucose-containing fluids, such as parenteral nutrition and a separate line, add their GIRs together.
Hospitals use their own protocols, and prescriptions should be double-checked by a second person. This calculator is a learning and checking aid for professionals.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.