Log in
Pernicious Anaemia Society
19,095 members13,112 posts

Is Active B12 rest a fasting test?

Hi all,

I’m struggling to understand why my two active B12 tests only a week apart are so different. The only difference was a)the time of day b) I fasted for the private one, but my GP told me not to fast for the nhs one.

Private 7am showed me as Active B12: 22.9

NHS 11.30am showed me as Active B12: 46

Any ideas please? Thank you

6 Replies

Thanks Hidden

For the NHS one I don’t have a range, simply >30 pmol/L, the private was 25.10-165 pmol/L.


Do you take biotin? It can effect b12, tsh and t4 lab test results, depending on the method the lab uses to test for them.


1 like

Hi KimberinUS

No, I don't take anything currently, so I'm really surprised that there's this difference!?


Sorry, i cant think of anything else that might cause such a variation in the lab results.

Due to the variation, i would ask for a third


Thanks KimberinUS

That's exactly what I thought.

I've been through everything, the only differentials were the time of day and one I fasted for and one I didn't.


Hi Hidden

I don't take ANY supplements at the moment?

1 like

You may also like...