How to reconcile a controlled drug log
Two numbers should agree. What left the container: the balance at the last count, plus anything received or opened since, minus what you count now. And what the records account for: volume on patient records plus recorded waste. The calculator below is prefilled with an example where they do not.
| Left the container (start + added - counted) | 22.3 mL (1,115 mg) |
| Accounted for by records (patient records + waste) | 21.9 mL (1,095 mg) |
| Difference (left the container - recorded) | +0.4 mL (20 mg) |
Runs in your browser; nothing you type is sent anywhere. Arithmetic for your records: we do not give legal or compliance advice.
The example
| Figure | mL |
|---|---|
| Balance at the last count | 18.4 |
| Received or opened since | 20 |
| Counted now | 16.1 |
| Left the container | 18.4 + 20 - 16.1 = 22.3 |
| On patient records | 21.3 |
| Recorded waste | 0.6 |
| Accounted for by records | 21.3 + 0.6 = 21.9 |
| Difference | 22.3 - 21.9 = 0.4 mL (20 mg) |
Tracing a difference, arithmetic only
- Re-add every entry since the last count. Most differences are an addition error.
- Look for an entry equal to the difference. A single missing or doubled entry shows up as exactly its own volume.
- Check for swapped digits: 0.54 mL written as 0.45 mL gives a difference of 0.09, and a swap of two neighboring digits always gives a multiple of 9 in the place where they sit.
- Check the unit of each entry. An entry written in mg on an mL log is off by a factor of the concentration.
- Run the container through the running-balance calculator entry by entry to see where the balance first departs from what you expect.
This finds arithmetic and transcription differences. It does not tell you what a remaining difference means or what to do about it. We keep and total your records; we do not give legal or compliance advice.
Questions
Which way round is the difference?
Here it is volume that left the container minus volume the records account for. Positive means more left than the records show; negative means the records show more than left.
Does this tell me whether my log is compliant?
No. We keep and total your records; we do not give legal or compliance advice. The calculator adds and subtracts the figures you type and shows where two of them differ.