The Recommended Daily Intake of B12 for people over age 14 is 2.4 mcg. So a 1000 mcg tablet is 416.67 times the RDI. A 500 mcg tablet is 208.33 times the RDI. But you can't take a specific amount really -your choice is to take either the 500 mcg tablet or the 1000 tablet (for purposes of this illustration; there are probably other choices available.). What you really need to calculate is the cost per pill. If you want to take 1000 mcg's/day, and the cost of a single pill is less than the cost of two 500 mcg's, that would be the way to go.

So, is one of my bottles mislabeled?

The price isn’t the issue here, and at any rate both bottles were free to me.

I think I need to look up the difference between RDI which you mention, Bestyears, and Daily Value, which is on the bottles. Off to Google!

Edit to add, AHA! The Daily Value changed, it actually went down. So the newer bottle that has fewer mcgs, does in fact have a higher percent of daily value.

And true about not being able to get the quantity of a vitamin you really want.

I used to take B12 shots and before & I learned our bodies will absorb what it needs and your urine gets rid of the rest. If B12 makes you feel that much better, you need to get your blood checked. It's serious if your low on B12.

I had to refresh my B12 knowledge again and found this website which is makes it easy to understand. Pay attention to what type of B12 to buy.

Harvard B12 info

I'm glad you brought the topic up because I've been off the shots for years due to anemia but I read as we get older we start losing B12 which contributes to Dementia which my mom had.