The answer appears to be that you can deduct your doctor's concierge medical fee in toto, provided you are paying for services that would be deductible in any case, and are not paying merely for access.
This answer is based on a source that I quote from below, and also from my (very reputable) CPA's acceptance of my list of medical expenses, which included the concierge fee in total, which was large enough that there was no conceivable way that the CPA could have not noticed it. I realize that this paragraph is not a 100% definitive answer, but, combined with the next part of my answer, it is surely enough to proceed on.
This Source says:
Deducting the retainer [earlier the Source called it the concierge
fee] itself plunges you into murkier waters. The IRS says retainers
may be deductible -- or a legitimate expense for a health savings
account -- depending on what you get for your money. If your fee pays
for you to get a physical once or twice a year, plus ready access in
emergencies, then you're paying for deductible services and the
retainer is also deductible. If all you get is access -- the fee
doesn't pay for any services -- there's no write-off. If part of the
fee is for services, that part is deductible. (Emphases Added.)
Of course, the head-scratcher is the last sentence:
If part of the fee is for services, that part is deductible.
It could be argued that if part of the fee is for services, then part of the fee is for access and that part is not deductible (except for access in emergencies). But almost anything can be (and often is) argued.
I argue that if the practice does not specify what part of the fee is for non-emergency access, then I have no basis to not deduct that part.