Vitamin B12 and Active B12 – What’s the Difference?

difference between b12 and active b12


So you thought you had a B12 deficiency but your test came back ok? Maybe it's Active B12 you need to be looking at. Here's the difference between the two.

In a Nutshell

The quick Version

What we mean by "B12"

Generally when we refer to "B12," we're referring to total B12.

The Body Can Only Use Active B12

Active B12 generally makes up no more than 30% of our total B12 levels but it's only this form of B12 that the body can use

Deficiencies in Active B12

You could feasibly get a total B12 test result that says your levels are absolutely fine but in reality, your active B12 levels might be low

What’s the difference between b12 and active b12?


The answer to this is pretty simple. Generally when we talk about “vitamin b12” or “b12 levels,” we’re talking about total level of B12 in our blood.

And that in itself is pretty straightforward.

But a test that measures your total B12 level might only be telling your half the story. That’s because your body can only use active b12 (the active form of the vitamin). And in most cases the active form of B12 typically makes up anything from 10% to about 30% of your overall levels.

Why does it matter?

Ever had a B12 test because you were exhibiting all the symptoms of a B12 deficiency?

And then did you find that test came back reading normal levels but you still felt certain you might have a deficiency?

Well, that’s one possible issue with testing total levels. It is absolutely possible to have completely normal total B12 levels but low active B12. And the result of that is that you’ll still exhibit the symptoms of a B12 deficiency because it’s the active b12 form that really matters.

Testing on the NHS

It’s quite common for NHS b12 tests to look for the total form.

So if you’re in the position of suspecting you might have a B12 deficiency and are being tested by your GP, request an active B12 test. If that’s not possible, there are lots of cost effective options in the form of home test kits you can always try and you can get them from as little as £30.


What are the symptoms of b12 deficiency?

There are a number of symptoms you may experience if you have low total or active b12 levels. They include (but are in no way limited to):

  • Low energy levels and fatigue
  • Anaemia
  • Pins and needles
  • A sore and particularly red tongue
  • Ulcers in your mouth
  • Visual disturbances
  • Issues with your memory or judgement
  • Psychological problems which can also include depression


Sources of B12

If you’re looking to increase your B12 intake, then there are a number of food types that are particularly rich in it. They include:

  • Animal kidney (in particular lamb kidney)
  • Liver (chicken, lamb or ox)
  • Sardines
  • Herring
  • Kippers
  • Eggs
  • Beef
  • B12 fortified cereals

(Not an exhaustive list).

Should I take a B12 supplement?

Most of us are likely to be able to get what we need from our diet. However, B12 is typically found in animal products, so this might be difficult for those following a vegan diet. In these cases, the NHS suggests a supplement could be useful.


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