As a player I have played Vampires before, but I have yet to find a DM who could answer these age-old concerns:
How much blood does a vampire need to drink and how frequently must the vampire drink that amount without suffering negative side effects? Does being a different kind of vampire like a warrior vampire or spellcasting vampire (MM pg 298) affect the amount normally required?
As a DM I would like a reasonable answer to this question; it's something I have wondered about for years.
Background information:
I'm building a society ruled by vampires where non-vamps must pay a "Blood Tax". You donate X amount of blood either weekly or monthly (haven't decided) and in exchange you are protected from being hunted. This makes the citizens feel safe and secure knowing that they won't be hunted and also saves the vampires the hassle of dealing with all of them hunting in the same area and causing a shortage of prey to feast on. The Hunt is reserved for criminals, rebels, and others who actively break the law of the land and is treated like a sport by the vampires.
Best Answer
Five liters per month, in a very narrow case.
Plane Shift: Innistrad (p. 17), as dubiously "official" as it is, answers this explicitly, because it's highly relevant to the setting (in which certain vampires follow a system much like you're describing).
Note that Innistrad vampires are not standard D&D Monster Manual vampires. Among other things, they're created by exchanging blood with a vampire rather than being killed and rising from the grave (making them not technically undead, though they do have the undead creature type).
Addendum: Since this is probably relevant to your question, the average recovery time for a 550-ml blood donation is about 36 days, which is 15.3 ml/day replenishment. Vampires eat about 5000 ml per lunar month or 179 ml/day. This comes out to about 12 humans needed to feed each vampire, and as a quick rule of thumb they can be "taxed" a pint of blood per month. That's 12 healthy, non-pregnant adults, minimum, to not starve. The actual number will be higher depending on reserve capacity and on how many children they all have. (And the vampires want that number to be as high as the local food supply can support. Vampires are immortal, so they only get to reproduce if the human population is expanding.)