Organize Information, Use Formula, and Solve

Determine what dosage is desired and what form you have the medication in. For an easy example, say that the dose is supposed to be 500 mg of medication A. You have medication A in 100 mg tablets.

Use the formula: (desired amount)/(amount available) x (quantity), or written simply: D/A x Q = X (unknown amount)

So, for the example of 500 mg of medication available in 100 mg tablets, we’d set it up as follows:

500 mg/100 mg x 1 tablet = X

Solve the equation and you get 5 tablets.

Now for a slightly harder example, involving IVs: Let’s say that the doctor orders 45 mg of medication B to be administered. You have medication B available in IV form in the strength of 20 mg/5 mL (20 mg of medication per 5 mL of solution).

Set the equation up as:

45 mg/20 mg x 5 mL = X

Solve the equation and you get 11.25 mL of solution needed to administer 45 mg of medication B.

Always consider whether your answer makes sense. If you put the numbers into the equation incorrectly, you can come up with radically different numbers, but they won’t make sense if you think through a rough idea of what the answer should be. As an example, in the first example, if you reversed the 500 and 100, your answer would be to give 1/5 of a tablet, which does not make logical sense if you consider the problem.

Tips

• Check and double-check yourself before actually administering the medication.