I heard that vitamin B12 absorption can vary based on time of day and the most recent mealtime, and also that acid-reflux drugs might interfere with B12 absorption. What is the optimal time of day to take vitamin B12 supplement?

  • I think this is true about all supplements or vitamin tablets. Although, I don't think it has to do with a time of day. Rather, it's about eating it with food, on an empty stomach or with specific foods: "In a mixed meal, many factors affect absorption of nutrients including other nutrients (e.g. vitamin C enhances iron absorption, zinc competes with copper absorption)" reddit.com/r/ScientificNutrition/comments/gh0xga/…
    – adamaero
    May 18, 2020 at 13:25

3 Answers 3


I'm not a doctor or another health professional, this is what I remember from my research when starting to take B12.

The most important thing is to take them regularly. B12 builds over time and is stored in the body (mainly the liver), so if your body needs some in the morning but you take your supplement at night, it will just take what it needs from its storage.

As for the time you take it, it depends on you :

  • B12 is best absorbed on an empty stomach, so it's best to take it in the morning after waking up. But it can upset the stomach of some people, for them it is best to take it after a meal.
  • It can also give a boost of energy, taking it before bed can cause insomnia or not having a restful sleep.

So technically it's best to take it in the morning, but if it's more convenient for you to take it at night and it doesn't mess with your sleep, nothing wrong with that either. As long as you take it regularly, that's the most important.

  • Can you mention a source for B12 being best absorbed on an empty stomach?
    – Nic
    Apr 17, 2019 at 4:31
  • Why not before a meal, like many other supplements?
    – bw3b
    Apr 17, 2019 at 7:27
  • @Nic I don't know
    – MlleMei
    Apr 17, 2019 at 9:29
  • @bw3b you can do that if you want, didn't say you couldn't
    – MlleMei
    Apr 17, 2019 at 9:30

I have GERD, and my doctor prescribed B12. Since I take my GERD medicine shortly before supper, she suggested that I should take my B12, and any other medicine that it would interfere with, around breakfast time.

As far as absorption goes, it also supposedly does pretty well sublingually (under the tongue), and if you take it that way, whether you've taken it before breakfast or after doesn't really matter so much. (It is, however, difficult to eat with a partially dissolved B12 pill under ones tongue, so during breakfast could be tricky.) I'm not really sold on it absorbing much better that way, but when I take it that way, it's already dissolved by the time it gets to my stomach, so it seems to me that it has to work at least as well as swallowing it and having it get part way into the stomach before it's completely dissolved.


I can only add that I'm looking up answers to this question right now because it's 5:49am and I haven't been able to sleep, having taken my first 100mcg B12 pill in mid-afternoon yesterday! I'm going to try taking it in the morning, from now on. I never have trouble sleeping, usually.

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