Common Registration Assessment, Part 1

Adrenaline dose calculations for anaphylaxis

Three original questions on intramuscular adrenaline doses by age and the volume to draw up, with the working shown.

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

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The Resuscitation Council UK anaphylaxis algorithm gives intramuscular adrenaline doses by age, using the 1 mg/mL (1 in 1000) concentration. The adult and over 12 dose is 500 micrograms (0.5 mL), 6 to 12 years is 300 micrograms (0.3 mL), 6 months to 6 years is 150 micrograms (0.15 mL), and under 6 months is 100 to 150 micrograms (0.1 to 0.15 mL).

The algorithm says to repeat the intramuscular dose after 5 minutes if there is no response, and to give an intravenous fluid challenge of 500 to 1000 mL for adults or 10 mL/kg for children. The Resuscitation Council UK anaphylaxis guidance page states that the most recent version of the guideline was published in May 2021, and its 2025 paediatric emergency drug chart gives the same intramuscular doses by age band (page and chart checked 14 October 2026).

The method

  1. Identify the age band and write the dose in micrograms.
  2. Check the concentration: 1 in 1000 means 1 g in 1000 mL, which is 1 mg/mL or 1000 micrograms per mL.
  3. Divide the dose in micrograms by 1000 to get the volume in mL of the 1 mg/mL solution.
  4. For a second dose, repeat the same dose and add the totals.
  5. For a fluid challenge, multiply the weight in kg by 10 mL/kg for a child.

Three practice questions

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

Question 1

A child aged 8 years has anaphylaxis. What volume of adrenaline 1 mg/mL is the first intramuscular dose?

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Answer: 0.3 mL

Working: The 6 to 12 year dose is 300 micrograms. 1 mg/mL is 1000 micrograms per mL. 300 ÷ 1000 = 0.3 mL.

Question 2

A child aged 4 years weighs 17 kg. They have a first intramuscular dose, no response at 5 minutes, then a second dose and a fluid challenge of 10 mL/kg. What total adrenaline in micrograms and mL, and what fluid volume?

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Answer: 300 micrograms (0.3 mL) of adrenaline and 170 mL of fluid

Working: The 6 months to 6 years dose is 150 micrograms. Two doses: 150 × 2 = 300 micrograms, which is 0.3 mL of 1 mg/mL. Fluid: 17 × 10 = 170 mL.

Question 3

Express adrenaline 1 in 1000 in mg/mL, and state how many micrograms are in 0.15 mL.

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Answer: 1 mg/mL, and 150 micrograms

Working: 1 in 1000 is 1 g in 1000 mL, which is 1 mg/mL. 0.15 mL × 1 mg/mL = 0.15 mg = 150 micrograms.

Exam approach

Pick the age band, write the dose in micrograms, then convert to mL using 1000 micrograms per mL.

Where marks are lost

  • Mixing up 1 in 1000 (1 mg/mL) with 1 in 10,000 (0.1 mg/mL).
  • Using the wrong age band, for example 150 micrograms for a child aged 8.
  • Giving micrograms as mL without dividing by 1000.
  • Forgetting that the doses on this page are for intramuscular use only.

Frequently asked questions

What is the adult intramuscular dose in the Resuscitation Council UK algorithm?

The algorithm gives 500 micrograms intramuscularly (0.5 mL of 1 mg/mL) for an adult and for a child over 12 years.

Is intravenous adrenaline used for anaphylaxis?

The algorithm says intravenous adrenaline for anaphylaxis is to be given only by experienced specialists in an appropriate setting, and that the intramuscular doses are for intramuscular injection only.

Sources

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

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More calculation topics

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