Pernicious Anaemia Society
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Venous Blood Specimen

My Dr has refered me to St. Thomas's hostpital London for a Venous Blood Specimen. I was self injecting once a week but she told me to stop injecting for one month. Will this test give an accurate reading of my B12 levels. I've not taken a B12 jab for 16 days and my old symptoms have returned. I don't know if the test is 100% true and if it's worth suffering without my B12 Jab. I also have MS, any info will be greatly appreciated. Thank you.

7 Replies

Sorry to hear about having to stop the jabs- know it is something I would find impossible to do.

The time periods for refraining from B12 supplementation are lower with the the active B12 test so a month should be enough. Might be better to try and contact St Thomas's to double check though.

Active B12 is a more precise test but my understanding is that there still aren't any guarantees even with that.


A word of caution, if the results return in the "normal" range, will your DR be tempted to reduce the frequency of your injections?

I get my blood tested once a year and expect the results to be >1500 pg/ml above the max limit of the test.

Without my blood levels being this high, I feel all my symptoms coming back.

The nature of nerve damage is such that any deficiency of B12 causes destruction of the myelin sheath, which takes forever to recover from, even at high b12 levels and doesn't really seem to repair at "normal" levels.

I wouldn't ever stop my b12 for whatever reason.


just to say that I think you are talking about different test - ie serum B12 rather than the holo-T/active B12 test which is the one done at St Thomas

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Will the serum B12 test give a precise reading..


serum B12 is the one that is normally done and is a long way from being precise. Active B12 looks at specific forms of B12 - those closest to the forms used at the cell level so a little more precise but still doesn't tell the whole story


Another thought: I also have a prescription of cyano 1ml of 1000mcg/ml per week. I actually inject 0.5 ml on Sunday and 0.5 on Wednesday.

For me, this levels off the highs and lows I was getting each week.

Are you on Hydroxocobalamin ? You should be able to last a month but if you have been injecting weekly, your body has gotten used to it.

I also split my daily folic acid. I take 2x 800mcg tablets in the morning and another 2x in the afternoon. Both occur before my commute to or from work and I find I am better able to deal with the stress.


I injected Hydroxo on Tuesday as I felt so rough. I also take a multi B vit, vit D 5000iu and 4 1000mcg of folate and drinking coconut water which befor I stopped injecting was making me feel well. Now 3 days after my injection I still feel extremely fatigued. I've had a cold for the last 2 weeks, can you advise me what I should do please. I have a box of Cianocobalamina 1.000 gammas which I've never tried, would taking this help? Thanks for all your help..


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