Common Registration Assessment, Part 1

IV fluid bolus calculations in children

Three original questions on fluid resuscitation volumes by weight and the rate needed, with the working shown.

Published 14 October 2026. Independent revision material, not GPhC questions, not for patient care.

A nurse holding a patient's hand beside a hospital bed
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

NICE guideline NG29 says children and young people who need IV fluid resuscitation should have a glucose-free crystalloid with sodium of 131 to 154 mmol/litre, as a bolus of 10 mL/kg over less than 10 minutes. For term neonates it gives 10 to 20 mL/kg over less than 10 minutes. This page covers children and neonates only: NICE removed the adult fluid resuscitation recommendations from CG174 in December 2025 because they are now covered by its sepsis guidelines.

NG29 also says to take pre-existing conditions such as cardiac or kidney disease into account, because smaller volumes may be needed, and to seek expert advice if 40 to 60 mL/kg or more is needed. Questions turn these into a volume from the weight and then into a rate in mL/h.

The method

  1. Choose the right group: child or term neonate.
  2. Multiply the weight in kg by the mL/kg figure for the group.
  3. For a neonate, calculate both the lower and upper ends of the range.
  4. To find a rate, divide the volume in mL by the time in minutes and multiply by 60 to get mL/h.
  5. NG29 says the bolus is given over less than 10 minutes. A question must give a time under 10 minutes for the rate to follow the guideline; a rate for exactly 10 minutes is only arithmetic.

Three practice questions

Work each one on paper first, then open the answer. All patients and prescriptions are fictional.

Question 1

A child weighs 14 kg and needs an IV fluid bolus of 10 mL/kg. What volume is given?

Show the answer

Answer: 140 mL

Working: 14 × 10 = 140 mL.

Question 2

A term neonate weighs 3.4 kg. NG29 gives 10 to 20 mL/kg for term neonates, not the 10 mL/kg used for older children. What is the range of volumes?

Show the answer

Answer: 34 mL to 68 mL

Working: Lower end: 3.4 × 10 = 34 mL. Upper end: 3.4 × 20 = 68 mL.

Question 3

A child weighs 24 kg and is to have a 10 mL/kg bolus. It is given over 8 minutes, which is within the NG29 limit of less than 10 minutes. What volume is it, and what rate in mL/h?

Show the answer

Answer: 240 mL, at 1800 mL/h

Working: Volume: 24 × 10 = 240 mL. Rate: 240 ÷ 8 = 30 mL per minute. 30 × 60 = 1800 mL/h.

Exam approach

Pick the group, find the volume from the weight, then convert to mL/h only if the question gives a time. Smaller volumes may be needed in some conditions, such as cardiac or kidney disease.

Where marks are lost

  • Using the neonatal range for an older child, or the child figure for a neonate.
  • Forgetting that a neonate has a range, not a single figure.
  • Dividing by hours when the time is in minutes.
  • Ignoring the note that smaller volumes may be needed in some patients.

Frequently asked questions

Does this page cover adults?

No. NICE removed the adult resuscitation recommendations from CG174 in December 2025 because they are covered by its sepsis guidelines, so no adult bolus is given here.

When does NG29 say to seek expert advice?

Seek expert advice, for example from the paediatric intensive care team, if 40 to 60 mL/kg of IV fluid or more is needed as part of the initial fluid resuscitation.

Sources

The questions above are original and use fictional patients and prescriptions. PreRegExamPrep is not affiliated with or endorsed by the General Pharmaceutical Council.

Practise until the method is automatic

Try 15 free questions with worked answers. No sign-up required.

Try 15 free questionsSee pricing

More calculation topics

See also the formula sheet, the eight sample questions and the approved calculator page.