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1. For drugs already in solution, check the amount of drug in each ml and the total amount of drug in the container.
2. Make sure you are clear about the dose units used. Most commonly prescribed are milligrams (mg) or micrograms.
3. Beware of drugs such as insulin and heparin, for which doses are prescribed in international units (which is sometimes, but should never be, abbreviated to i.u. which can be misread as 10).
4. Check the dose on the prescription and that it is expressed in the same units as on the medicine label.
5. If the prescription and the medicines label use different units of strength, refer to the conversion table and calculation examples on pages 4 and 5.
6. Once you are sure that the units are the same, divide the required dose by the amount of the drug in the ampoule and multiply by the volume of solution in the vial or ampoule.