Technically you could also deliver a low dose intravenously as well, so that’s not really a complete descriptor either. A more clear descriptor for a lay audience might be “high dose intravenous”.

But this actually still misses a small nuance, which can be understood once we know the context of how scientists tend to use the jargon of “pharmacological dose”. In bio research, we use this term mainly in contrast with “biological dose”. A biological dose refers to something relatively within the range of what could occur naturally within the body, through food consumption and/or the body’s creation of that chemical, depending on which chemical we’re talking about.

A ‘pharmacological dose’ is something significantly higher than what would occur naturally in the body. In this case with vitamin C, it’s more possible to achieve a “pharmacological dose” through IV (although with many other chemicals you can achieve a “pharmacological” dose orally if there’s not much restriction on absorption). Anyways, the point is that even saying “high dose” is not fully informative, because the scientist could be referring to just a high ‘biological dose’. Saying pharmaceutical dose gives a nod to the relative scale of the dose that we’re talking about.