1mV (millivolt) isn't right. Do you mean 1ma (milliAmps)? Voltage should always be 11.5v-12.5v. Electrical Current (Amps) is what you measure your drain in. Voltage is electron "pressure", Amps is amount of electron "flow". You want to measure the flow.
If it's 1 ma...that should not be an issue.
Did you check the drain from the Battery to a battery terminal first? With the car OFF, disconnect a battery terminal and put it in SERIES with the Multimeter. Set a high setting for AMPS and one lead in the Amps port. Anything above a few milliAmps is cause for concern. THEN you go to looking for fuses.
Also, when the car is OFF, what is the voltage across the battery terminals? A resting battery should be like 12-12.5v (I've seen 11.8v on a working battery).
When the car is RUNNING, what is the voltage across the battery terminals? To charge a battery you MUST have a higher voltage to "push" electrons into the battery from the alternator. You should get above 13v. Preferrably 13.5v-14v. Higher than 15v...and you're dealing with an overcharge scenario which will drastically shorten the life of your battery.
If your voltages at the battery are good...the alternator should be OK. If you have no parasitic drain from the battery other than a few mA, then it's looking like your battery needs to be load tested at any autoparts store.
Do you have corrosion at either of the battery terminals? If so, you have a bad connection at the battery. This will require a new terminal end installed or a new cable. Cleaning the terminal will help for a while, but the problem will eventually come back...potentially a year or so later. Take the cable off...bend it around..inspect it for cracks. Listen for internal popping and crackles which indicate internal corrosion. A car's starter needs a crap ton of current and if the cable is too bad, not enough current can go through it...then it will not start...but all the accessories will work...so often the battery is blamed.
Keep us posted.
If you find a large parasitic drain at the battery...and you check for drain at all the fuses (many cars have MULTIPLE fuse banks in the engine bay and the cabin)...and the drain from all the fuses does NOT add up to the total....then you have a short somewhere else. I would start looking at anything wired directly to the battery...or a short through the starter.
Good info. Will try these when I have the time. Thank you.