Pharmacy Technician Math

This page is on Pharmacy Technician Math. To ask or answer a question, scroll down the page to the Question and Answer section.

When you are working in a pharmacy there are some basic math calculations that you will use every day.

It's important to have a solid understanding of these calculations, to ensure that you can accurately translate the amount of medication that is prescribed into a usable form for the patient.

The most common calculation will happen when the amount of medication prescribed does not exactly match an amount in a dosage form.

For example, if a prescription calls for the patient to take 3 grams of medication daily. The only pills you have available are 500 milligram capsules.

To convert the prescribed dosage to milligrams, multiply grams by 1000. This means the prescription calls for 3000 milligrams daily, or six 500 milligram capsules.

The key to being able to do these pharmacy technician math calculations quickly is in being able to understand the important information that is on the prescription.

Information for tablets and capsules lists the amount or dosage of medication per unit, liquid medications are listed in medication per volume of liquid, and injectable solutions are listed as medication per volume injected. Side note: to learn more about the differences between tablets, capsules, liquid medications, and injectable solutions, see Pharmacy Dosage Forms.

The prescription will list a total amount of medication. So just like in the example above, the first step is to convert the amounts of medication to the same unit of measurement.

Milligrams to grams or vice verse will be the most common conversion. And it's easy to remember that 1 gram is equal to 1000 milligrams.

The most common systems of measurement you'll encounter will be Metric, American Standard, and the apothecaries' system.

It can also help to carry a pocket reference guide that has conversion information listed. This will make it easy to ensure you know the correct conversion to use.

It's also important to understand how to work with Fractions and Decimals.

Not every dosage conversion will work out easily with whole numbers, so it's good to be comfortable working with fractions and decimals.

To convert between the two forms, simply use a calculator to divide the top number by the bottom number. Five-eighths for example, you would enter 5 divided by 8. This returns .625, which is the correct decimal form for five-eighths.

Ratios and concentrations will also be an important part of the daily math used in a pharmacy.

For example, if a solution is 20% medication by volume, you need to understand how much medication is delivered in a 50 milliliter injection. In this case, 20% of 50 is 10, so the amount of medication in that dose would be 10 milliliters. Click here for more on IV Infusion Calculations.

The last main use of math in the pharmacy is to calculate days supply. Days supply refers to the number of days the physician wants the patient to take the medication.

A common default is a 30 day supply. This means you need to ensure they have enough individual daily doses to last for 30 days total. If they need to take four tablets every day, then the 30 day supply would be 120 tablets total.

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Links on this Page:

What is a Prescription?

IV Infusion Calculations

Pharmacy Dosage Forms

The Metric System

American Standard System

Apothecaries System of Measurement in Pharmacy

Understanding Fractions for Pharmacy Technicians

Understanding Decimals in Pharmacy Calculations

Figuring Days Supply on Prescriptions