Drug calculations

Drug calculations


Figure 79.1 Principles of drug calculations


It is vital that paediatric nurses have sound numeracy skills to assist them within a range of health care activities. One such activity is drug calculation and administration. Poor numeracy skills may lead to medication errors. While recognizing that medication errors are multifactorial, lack of competence in basic calculation is often reported as a key area of concern for many trusts (Fry and Dacey 2007).

Nursing and Midwifery Council

To ensure that nurses are equipped with a high level of numeracy skills the Nursing and Midwifery Council (NMC) has established key competencies within the Essential Skills Clusters for pre-registration nursing students that must be met in order for students to be allowed to progress onto the professional register (NMC 2010a). It has also provided standards for some post-registration qualifications (NMC 2010b). However, many qualified nurses do not feel confident in their numerical competence and that they would benefit from regular revision of the common numeracy skills required for the calculations undertaken within their area of practice (Fry and Dacey 2007; Hutton 2009).


The NMC has determined that nurses must be proficient in long division, multiplication and fractions to undertake drug calculations successfully (NMC 2010b). There are several resources that could provide assistance to nurses in utilizing a multifaceted approach to drug calculations. These include being exposed to drug calculations within their area, having basic numeracy knowledge, possessing calculator skills and being proficient in the effective use of equipment, such as syringes (Wright 2009).


Being able to estimate the answer soughtis essential in drug calculations. Many medication errors occur as the practitioner has not thought through what a sensible answer or dose would be. A moment taken to approximate the calculation will prevent serious errors, such as a misplaced decimal point (Hutton 2009).

Using a calculator

Paediatric nurses should be able to undertake non-complex drug calculations without the use of a calculator. A calculator provides an answer to the equation that is keyed in; if the equation is incorrect it is easy to generate the wrong answer. However, it would be acceptable to calculate the dose needed and then check the answer using a calculator. For more complex drug calculations, it may be necessary to use a calculator, although the correct answer should be estimated to ensure the calculation is correct.

Checking the dose

Before administering a drug to a child the nurse must be sure that the prescribed dose is correct. While errors may be made by prescribers as well as those who administer the prescription, accountability sits with both. Double checking is recommended for complex drug calculations. Checking must involve each nurse independently undertaking the calculation and then both checking the answer together (NMC 2010b). There are some academics who believe that double checking may increase the risk of error as each become complacent and rely on the other to spot an error. This is why it is imperative that nurses undertake the calculation independently before doing it jointly.

Recommendations for practice

Medication administration incidents are most frequently due to the wrong dose, delayed or omitted medication or the wrong medication being administered (NPSA 2009; Nursing Times 2012), with the most frequently cited error being calculation error. Health care organizations must ensure that they implement routine and regular assessment of their clinical staff’s numeracy skills. This should form part of their mandatory clinical update and continued professional development. It is hoped that the implementation of such strategies will lead to an increased awareness of the importance of numeracy and thus an improved quality of care of patients and a reduced risk of medication errors (Warburton 2010).

Jun 7, 2018 | Posted by in NURSING | Comments Off on Drug calculations
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