Pernicious Anaemia Society
15,518 members10,920 posts

Will oral B12 complicate blood test results?

Hello, My apologies if this post is redundant--I thought I posted it yesterday, but it seems to have vanished. I was diagnosed with low Vitamin D in April and low B12 (148) in August. I am in the US. I received daily injections for 7 days, followed by 4 weekly injections, and now monthly "forever." I continue to have muscle twitches throughout my body. It's hard to say whether or not they are improving. I saw a neurologist who would like to see my levels at 800. At last check, they were around 600 about 2 weeks after the prior injection, but I had started taking oral B12 (1000 mcg) and Vitamin D3 (2000 IU) daily. My doctor supports monthly injections and I have learned to do them myself. Our current plan is to retest my B12 1 month after the last injection, but having taken the oral B12 and D all along, to try to sort out whether this is an absorption issue or another cause, because I would like to know. The low vitamin D along with the low B12 supports poor absorption, but it is not unusual to have low vitamin D after a New England winter. I'm being told that intrinsic factor is no longer tested, and that a diagnosis of PA is a process of elimination. My question is whether or not the B12 results will be accurate if I've been taking oral B12 for the past month?

4 Replies

My question is whether or not the B12 results will be accurate if I've been taking oral B12 for the past month?

They will be accurate, in that they will reflect the amount of B12 in your blood. If you're asking if that amount will have been affected by the oral B12 you've been taking. Yes. They key is - by how much?

If your B12 deficiency was do to an absorption problem then the oral supplements will have raised your blood levels by a small amount. If it wasn't due to an absorption problem then they will have raised quite a bit.

1 like

Thank you! That makes sense to me and is what I thought. I just didn't know if the blood levels accurately reflect what is going on at the cellular level, or if there will be an excess of B12 in my blood because of the supplementation that doesn't accurately reflect the absorption.


I wouldn't worry too much about the cellular level. The number of cases where blood levels and cell levels are very few and far between. You could always ask for an MMA test. Methylmalonic acid is a chemical used up in one of the cellular reactions mediated by B12. If there's not enough B12 in the cell then MMA levels will rise. If they're not high then it means your cellular levels of B12 are OK.


Great--thanks so much! I really appreciate your help!


You may also like...