When should someone do the Active B12 test.

[islandgirl1986]

Hi. I am on 3 monthly injections of B12 and high reading of 1500. Is it worth having an Active B12 test done. thankyou

[Laura5]

I think it is unlikely to be helpful if you are getting injections.

[islandgirl1986 in reply to Laura5]

Thankyou. I thought it was a test to tell exactly how much b12 was getting to the cells.

[engels in reply to islandgirl1986]

The Active B12 test just measures the amount of active B12 in the blood. This is one step better than the standard test which only measures total B12 (i.e. both active and inactive) but it still does not show how much B12 is actually getting to the cells.

Having either the Active B12 test or the standard B12 test is pointless for anyone already having injections.

[Laura5 in reply to islandgirl1986]

That should be how it works - unfortunately it has problems. See this recent post by fbirder

healthunlocked.com/pasoc/po....

[Hidden]

The general view is that once you start injections or oral supplements, then the results of tests will be skewed. The guidelines your doctor should have read say this.

[islandgirl1986 in reply to Hidden]

Many thanks. I thought it told you how much B12 gets into the cells.

[Hidden in reply to islandgirl1986]

I think there is an element of error in all the tests. The guidelines say that doctors should treat more on symptoms than blood results. I know that only between 8 and 20% of the serum b12 level is supposed to be active. So with my level of 270 it is 54 at best!

[islandgirl1986 in reply to Hidden]

Yes I have read that maybe only 20% gets to cells. I'm at 1500 which according to them is above range by 600, but my gp says keep injections going 3 monthly. Yes, your level appears to be very low. 

[fbirder in reply to islandgirl1986]

It tells you how much holotranscobalamin there is in your blood. B12 is carried about in the blood attached to two different proteins, but only one can enter the cells. The active B12 test looks for this TC2-B12 combination. 

If you're B12 deficient then your holotranscobalamin levels will be low. But it seems that it's not any better than testing for normal B12.

In theory one could be deficient in the TC2 protein, possibly because of a mutation in the TCN2 gene (that makes TC2). I have a mutation in one of the two copies of this gene, but it seems that just one working copy is enough to provide enough TC2.

The link that Laura5 posted above suggests that the MMA test is the best option for checking for functional B12 deficiency.

[islandgirl1986 in reply to fbirder]

Thankyou for info

[Sleepybunny]

Hi,

This link is from a company that produces  Active B12 tests. See the 4th question in list.

active-b12.com/frequently-a...

[islandgirl1986]

Thanks so much for info