Drug dosage calculation requires knowledge, precision, and accuracy. Good numeracy skills and basic mathematical proficiency are essential to ensure patients receive the correct prescribed dose (1). Poor numeracy and calculation errors can have significant consequences for patients. Between 2020 and 2024, 243 serious incidents related to medication management were reported (2). These incidents involved dosage errors, administration of incorrect medication, and inadequate follow-up of medication treatment. Of the 243 reported incidents, 37 percent (89 patients) had fatal consequences and 28 percent (69 patients) resulted in severe injuries (2).

Failure rates and errors in dosage calculation

In 2018, failure rates at universities and colleges for medication dosage calculation exams in nursing studies ranged from 8.8% to 61% (3). The most common medication calculation errors usually involve incorrect dosage calculation and administration to patients (4). Painkillers like morphine are among the medications where a tenfold overdose has been reported due to a misplaced decimal point or zero (4). Other medications with reported calculation errors include insulin, parenteral nutrition, oxycodone, and digoxin (4).

Most errors occur with intravenous administration

Out of 100 reported and investigated medication management errors in 2022, 70 cases involved errors with intravenous administration, meaning drugs given as infusions or injections (4). Dilution of medications, in particular, was associated with a high risk of errors in medication management, as were incorrect settings on infusion pumps (4).

Too high workload and failure in double-check routine?

It is a known fact that the workload and demands for efficiency among healthcare personnel do not align with the available resources or time. In hospital wards, a nurse can be responsible for up to 8-9 patients as the primary nurse. In other words, the margins are not in a ward nurse's favor if one of the patients deteriorates and requires rapid medical treatment and a higher level of monitoring. In municipalities, there is high time pressure to get through long patient lists. The pressure seems particularly high in home care services, where many employees are unskilled or temporary staff, and who largely work independently without the possibility of performing double-checks (2). However, elderly people over 65 are most vulnerable to medication-related errors (2). Co-morbidity and polypharmacy can result in serious consequences due to drug interactions.

So, what's the problem?

• Do we work in a system where demands for efficiency compromise patient safety?
• Is there enough focus on medication dosage calculation in education?
• What routines do hospitals and municipalities have regarding medication dosage calculation? Is an annual refresher required? Are enough deviations reported for incorrect medication management?

References:

(1) Olsen, L. A. Practical medication calculation – dose – strength – quantity. 5th ed, 2nd printing; Oslo: Cappelen Damm; 2022.

(2) Dolonen, K. A. 243 serious incidents related to medication errors were reported – 89 of these were fatal. (2025). Available from: 243 serious incidents related to medication errors were reported – 89 of these were fatal

(3) Dolonen, K. A. & Hauge, N., E.H. Medication calculation: Zero tolerance for errors. (2022). Available from: Medication calculation: Zero tolerance for errors

(4) Hernæs, N. Medication calculation: Where does it go wrong? (2022). Available from: Medication calculation: Where does it go wrong?

Written by Julianne Kvernstuen, intensive care nurse