Dose vs Dosage

Despite repeated emphasis upon the distinction between dose and dosage, the two terms continue to baffle many writers. As we’ve often been told, dose refers to a specified amount of medication taken at one time. Dosage, however, refers to the administering of a specific amount, number, and frequency of doses over a specified period of time. Dosage includes chronological features, specifically duration and periodicity. The best way to remember the distinction between dose and dosage is to focus on the meaning of the suffix –age in dosage. Dose will then be understood by default.

The suffix –age has several meanings. For instance, place or residence (orphanage, a place that houses orphans), relationship, connection (parentage), an action (blockage), a social condition (peerage), and a few others. But the meaning that’s relevant here is ‘collection’ or mass, overall amount: The suffix is added to a singular noun, which is semantically specific.

For instance, driving to and from work you travel a certain number of miles a day. However, the number recorded on the odometer (or milometer) represents the mileage, the total number of miles the vehicle has traveled up to a certain point in time. Dose and doses are comparable to mile and miles, respectively. Dosage is comparable to mileage. A “dosage regimen” refers to the number of doses of a drug or medication that a patient is supposed to take (or to be administered) over a specified period of time, and the individual doses that comprise the regimen are usually scheduled.

For example, 300 mg of a gabapentin capsule represents a dose of this seizure drug, whereas 300 mg of gabapentin 3 times a day (i.e. a total of 900 mg of gabapentin per day) represents the dosage regimen of the drug. [For details on this drug reference, see the article “Gabapentin” (online) by the Epilepsy Foundation, www.epilepsy.com] A “dosage regimen” is also sometimes called a “dosing regimen”.

Terms belonging to the same set as dosage and mileage convey a cumulative effect. Thus a chronological sense of duration constitutes an important semantic feature of these words. Here are several words that belong to the same set as dosage and mileage: acreage (vs. acres), cordage (vs. cords), foliage (vs. leaves of a plant), “footage” [of cinema film, or of size and length] (vs. feet), plumage (vs. feathers), tonnage (vs. tons).