Drug calculation skills for nurses

It is estimated that 237 million medication errors occur in the NHS in England every year across acute, community, general practice, learning difficulties and mental health settings.

Drug calculation skills are applicable to all nurses, being one of the standards of proficiency expected of NMC registered nurses from the start of, and throughout, their careers.

Examples of common medication errors relate to the wrong:

  • Patient;
  • Medication;
  • Dose;
  • Calculation;
  • Route;
  • Time.

Most medication errors are caused by health professionals and can result in patient harm and even death. The most frequently cited error – the wrong dose – stems from drug calculation errors. This can be a result of not understanding the units of measurement for a particular medicine, such as micrograms, using the wrong drug strength to measure doses or making mistakes in calculations which leads to the incorrect dose being given or the wrong rate of administration.

Between April 2015 and March 2020 NHS Resolution received 1,420 claims relating to errors in the medication process (prescribing, preparing, dispensing, administering, monitoring or providing advice on medicines). Of the 1,420 claims received, 487 were settled at a cost to the NHS of £35 million (excluding legal costs).

The most common medications to be cited in error incidents involve anticoagulants, opioids, antimicrobials, antidepressants, and anticonvulsants, according to initial data from NHS Resolution published in March 2023.

Drug calculation skills are essential to ensure patient safety and, after studying our learning unit, you should be able to:

  • Explain different units of measurement used for medicine dosages;
  • Correctly calculate dosages for medicines in tablet and capsule form;
  • Correctly calculate dosages for medicines allowing for the weight of a patient;
  • Correctly calculate dosages for medicines that are in suspension or solution;
  • Correctly calculate the administration rate for continuous IV infusions of medicines and fluids;
  • Recognise incorrect dosages of medicines and know how to ensure patient safety.

Visit the unit here.


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