Leading and Trailing Zeros: The Medication Safety Rule
Leading and trailing zeros: Write a zero before a decimal point (0.5 mg, not .5 mg) and none after a whole number (5 mg, not 5.0 mg), so a missed decimal point can't cause a tenfold error.
Two writing rules prevent tenfold dosing errors:
- Always a leading zero. Write 0.5 mg, never .5 mg. A “naked” decimal point is easy to miss, and .5 mg read as 5 mg is ten times the dose.
- Never a trailing zero. Write 5 mg, never 5.0 mg. If the decimal point is missed, 5.0 mg reads as 50 mg.
Both are on the ISMP list of error-prone dose designations, which marks them as items on The Joint Commission’s “Do Not Use” list. The Joint Commission allows a trailing zero only where a value must show its precision, such as a lab result or a catheter or tube size; a medication dose is not one of those.
Exams follow the same rule. When a question says to round to the tenth and the answer is a whole number, record the whole number, without “.0”, unless the exam’s instructions say otherwise. Every answer on this site is written that way.
Sources
- List of Error-Prone Abbreviations, Symbols, and Dose Designations — Institute for Safe Medication Practices (ISMP)
- Do Not Use List: trailing zero FAQ (Information Management) — The Joint Commission