Pharmaceutical concentration units
Drug concentrations in clinical practice get expressed in at least 5 different ways, often on the same drug label. Getting these wrong is a serious patient safety risk, particularly for high-alert drugs like adrenaline, local anaesthetics, and concentrated electrolytes.
Conversion reference
| Unit | Definition | Conversion to mg/mL |
|---|---|---|
| mg/mL | Milligrams per millilitre | × 1 (base unit) |
| % (w/v) | Grams per 100 mL | × 10 (e.g. 1% = 10 mg/mL) |
| mcg/mL | Micrograms per millilitre | ÷ 1000 |
| g/dL | Grams per decilitre (= per 100 mL) | × 10 (same as %) |
| Ratio 1:X | 1 gram in X mL | 1000 ÷ X (e.g. 1:1000 = 1 mg/mL) |
The adrenaline example
Adrenaline 1:1000 = 1 mg/mL. Adrenaline 1:10,000 = 0.1 mg/mL. The 1:10,000 concentration is used for IV cardiac arrest; the 1:1000 for IM anaphylaxis. Giving 1:1000 IV instead of 1:10,000 delivers 10x the intended dose. This error has caused cardiac arrests. The ratio notation exists precisely because these concentrations were established before mg/mL labelling was standard.
Related tools
For IV infusion rate from a concentration, see IV Drip Rate Calculator. For weight-based dosing, see Weight-Based Dose Calculator. For volume unit conversion, see Volume Converter. For lab value unit conversion, see Lab Values Converter.