[NoImmatureAdHom]

I can think of three ways:

1) "Hi doc, I'm thinking about ways to better hedge tail risk as I get a little older. In the case of this particular med, obviously it'd be really bad to be without it for [2 weeks, whatever]. People were without meds for that long in [Katrina, other example disaster]. So, I'd like to have a supply on hand. Can you prescribe me [a month] extra?

2) Lie. "Hi doc, I'm going to [really far-flung place, Alaska] on a [long, 3-month] expedition. I need to have my meds. What should we do?

3) Skip the bullshit and, assuming they're not controlled substances, just order directly from an Indian / Canadian pharmacy online.