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. See Resuscitation Council UK guidance on adrenaline administration. 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.