Yes, Jonathan, I think we understand after the 100th time~ (kudos to people who know this reference, and sorry to those that don't.)

Hello and thank you for downloading! This little mod adds 240 small rats called 'tasty rats' which, when killed, drop a bottle of human blood for vampires. Now vanilla game, human blood doesn't help with your vampire stage, but there's some mods out there that fix this, which is why I made it human blood instead of rat blood. In the future if I figure out how to make a universal script that works for like... at least some overhauls, I'll make it more immersive by calling it rat blood or even making it so just clicking on the rats feeds you on the spot.

A lot of them are in various imperial city sewers, including the starter sewers, though not too many since I know they'd be kinda impossible to get to past the start of the game. One or two can also almost always be found around beggar's camps, stables, farms, wilderness camps and such. There's a few in other random places that make a little bit of sense. But they mostly stay around people so you won't find any in caves/ruins. They also respawn so if you need rats again you can try to remember roughly where they were, though they do wander.

I mostly made this for a good vampire playthrough, most mods encourage evil playthroughs which is fine but.... Options~ And the idea came to me because of the video game titled 'Vampyr', where you play as a vampire that, when needed, you eat rats for blood.

Requirements:
Nothing exactly, but for the blood to do any good, you need a mod that enables the human blood bottles to actually lower your thirst. I'll list some mods that I know do so. You only NEED ONE so don't freak out and think you need all of these lol. I'm just listing all the ones I've found that does this. There are probably others too.

This one everyone should have anyway but just in case... https://www.nexusmods.com/oblivion/mods/5296
This one is ALL it does, so very lightweight: https://www.nexusmods.com/oblivion/mods/30959
This one is also really lightweight, but it also adds a merchant to buy the blood from: https://www.nexusmods.com/oblivion/mods/45561
This one is a heavy vampire overhaul and the main reason why I didn't add my own script. This one has the human blood bottle fix and also does a lot more, up to personal preference if you like what it changes: https://www.nexusmods.com/oblivion/mods/45116
This mod is a Primary Needs mod that also affects vampires, but in exchange bottled human blood has been fixed: https://www.nexusmods.com/oblivion/mods/37088
This one is another vampire overhaul but not as large as the previous overhaul: https://www.nexusmods.com/oblivion/mods/36408
Another vampire overhaul, one that I may personally use for immersion purposes of the chapels: https://www.nexusmods.com/oblivion/mods/36189

There's probably loads more of other fixes out there but I rather not search all of nexus for them if you don't mind.

Credits:
Bethesda for the game and CS
Me for... wasting 3 hours on this XD.
DONTNOD for making Vampyr and giving me this idea with their game.