Difference Between Drug Dose and Dosage

People often use dose and dosage interchangeably, but these terms have different meanings. Adding the suffix -age to the base word "dose" implies an overall amount. It can be compared to the difference between the words mile and mileage.

This article describes the difference between the two terms and provides examples of each.

What Is a Dose?

The term "dose" refers to a specified amount of medication taken at one specific time.

According to the American Medical Association (AMA), drug doses are expressed in metric mass units—for example, milligrams (mg) or milligrams per kilogram (mg/kg). Some drugs, such as insulin or heparin, may be prepared as mixtures. For that reason, they have no specific molecular weight and can't be described in mass units.

There are a few exceptions, though. Liquid medications for the eyes and ears are sometimes measured in drops. Some medications are measured in grains. And other medications are dispensed using apothecary system measurements like teaspoonfuls, ounces, or drams. However, these are rare.

Examples of Dose

Different types of Tylenol (acetaminophen), for example, come in different doses. The type and dose you choose depend on the condition being treated.

Here are some different Tylenol doses:

• For adults and children 12 years and over, a single dose of Extra Strength Tylenol is 1,000 mg (two caplets) of acetaminophen.
• For adults and children 12 years and over, a single dose of Tylenol Regular Strength Liquid Gels is 650 mg (two capsules) of acetaminophen.
• For adults and children 12 years and over, a single dose of Tylenol Extra Strength Severe Cough + Sore Throat Night Liquid is 30 milliliters (mL).

The age of the person taking the medication can also make a difference, especially with babies and children. In some cases, dose instructions for children may simply state "ask a doctor."

What Is a Dosage?

The AMA defines a dosage as how to take or give a medication as prescribed. "Dosage" is a much broader term than "dose." It involves a specific amount, number, and frequency of doses over a specific period of time.

Examples of Dosage

Here are some different Tylenol dosages:

• Adults 12 years and over: For minor aches and pains, take two tablets of Regular Strength Tylenol every four to six hours as needed. Do not take more than 10 tablets in 24 hours.
• Adults 12 years and over: For more severe aches and pains, take two Extra Strength Tylenol caplets every six hours as needed. Do not take more than six caplets per day.
• Adults 18 and over: For arthritis pain, take two Tylenol Arthritis Pain caplets with water every eight hours as needed. Do not take more than six caplets per day.

The antibiotic eye medication ofloxacin is taken in drops. One course of ofloxacin is seven to nine days, depending on the indication prescribed by your healthcare provider.

For bacterial conjunctivitis (pink eye), dosage instructions for ofloxacin look like this:

• Days 1 and 2: Use one to two drops every two to four hours in the affected eye(s).
• Days 3 through 7: Use one to two drops four times daily.

Summary

The words "dose" and "dosage" don't mean the same thing. A dose is an amount of medication you take at one time. Doses are usually measured in metric mass units such as milligrams. The dosage is a set of instructions for how to take the medication. It includes how much to take, when to take it, and how long to take it.