Focus on patient safety - "Medicinal product dose calculation. The rule of three must remain the rule."

Flash sécurité patient - Posted on Jan 17 2022


The yearly report on care-related serious adverse events showed, from 2018, that adverse events related to medicinal products were the third most common cause behind the serious adverse events reported. Among these medication errors, dose errors are the most commonly reported type of error (169/362) with dose errors related to incorrect dose calculation being over-represented (80/169).

The 3 types of errors which can be generated by a dose calculation are[1]:

  • the dose error itself,
  • incorrect flow-rate,
  • administration time error.



By sharing this feedback from healthcare professionals confronted with theses care-related serious adverse events, this information sheet can be used:

  • alert healthcare professionals as to the recurrence of serious adverse events due to calculation errors and to their consequences and raise their awareness as to the absolute necessity of managing the rule of three;
  • alert all training professionals of the need to reinforce learning and proficiency in mathematical reasoning as part of training modules for all healthcare professionals;
  • reinforce provision of information to healthcare professionals on good administration practices, especially through routine double checks.


So it doesn’t happen again

This information sheet highlights the failings of all the healthcare professionals in the use of calculation basics (units of mass, volume, time, conversions, concentrations, dilutions, flow rates, etc.) and in the rule of three.

Analysis of the deep-rooted causes and defective barriers, shows that double-checks are not routine, for medicinal products considered to be high risk, for medicines for injection, and generally for all preparations needing to be made up first, regardless of the stage of medication management; non-routine double checks combined with task interruptions.

[1] , Afssaps: French Agency for the safety of Health Products (Agence française de sécurité sanitaire des produits de santé), replaced in its activities by the French National Agency for Medicines and Health Products Safety (Agence nationale de sécurité du médicament et des produits de santé - ANSM), on 1st May 2012


Contact Us

Service Évaluation et Outils pour la Qualité et la Sécurité des Soins (EvOQSS)

See also