Is this an acceptable rise in B12? - Pernicious Anaemi...

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Is this an acceptable rise in B12?

Hi everyone,

First time poster in this group. I'm a 36 y/o female with hx of fibromyalgia and Hashimotos. Last fall, I began to notice vertigo and palps as well as frequent insomnia.

In January this year, woke up with heart rate of 150 bpm in the early morning hours. Ended up in the ER because I didn't know what was going on. Was told it was sinus tachycardia - essentially, fast rate but normal rhythm. 30 day heart monitor has since confirmed episodes of sinus tachy without any arrhythmia. Still going through testing, but cardiologist thinks my continuing symptoms (elevated heart rate, palps, headaches, pins and needles in feet/legs, dizziness, muscle weakness, tremors) are tied to some type of autonomic dysfunction.

PCP did test b12 back in January - it was 200. She had me do once monthly injections for 3 months. Just retested and level is 390 pg/mL (200-900 range).

Going for follow-up visit this week and wondering if I need to continue to push for more injections and/or PA testing. I'm not sure how much to expect b12 to increase over the course of 3 injections? I also take a multivitamin that contains 15 mcg of methyl form of B12.

For reference, my b12 in January 2017 was 1000. I also had low vitamin d that has since been resolved as well. Last thyroid check was perfect, still waiting on most recent thyroid results.

Is this an acceptable increase in b12?

8 Replies

Forgot to mention there were two and a half weeks from final injection to lab retest.


after a shot your serum B12 will be off the top of the top of the measurable scale and will then fall over time as most of it is filtered out by your kidneys. The length of time this takes varies from individual to individual.

The normal range doesn't really apply after B12 shots and it's impossible to say, because there is so much more variation in levels that individuals need after shots - if any serum B12 level is right for any particular individual.

How do you feel. If you feel okay then this level is okay for you. If your symptoms have come back then you probably need higher levels now.


Unfortunately, I'm still having all the symptoms mentioned above: tachy episodes, muscle weakness, pins and needles in legs/feet, dizziness, etc.


15mcg of B12 isn't going to do much if you have an absorption problem - which is the most common cause of a B12 deficiency.

Is your thyroid under control?

Did you notice an improvement whilst you had the shots and it has since reversed? if so then the point at which it reverses is the point at which you need to have another shot.


Last test, thyroid numbers a few months ago were:

TSH 1.38 (.30-3.8)

FT4 1.4 (.8-1.8)

FT3 3.22 (2.3-3.8)

Additional results:

Folate 13.7 - no ref range given

Iron 64 (39-145)

Ferritin 88 (20-324)

TIBC 337 (260-445)

UIBC 273 (110-370)

% Sat 19 (20-55)

Just retested thyroid numbers yesterday so still waiting on new numbers.

From what I can,remember, I felt good when B12 was 1000. Just don't know if my symptoms are related to B12 or something else. Is it worthwhile to test for PA to determine if I have true absorption issue?


given that the test for PA isn't that senstive - gives false negatives 40-60% its a bit difficult to advise - it is useful to know what the absorption problem is - if you are deficient the assumption should be that it is absorption unless your diet has been totally lacking/restricted in B12 for a number of years (strict vegan with no supplementation or very little by way of animal products). Different absorption problems have different potential consequences so it can be useful to know what else to look out for.

Having hashi's makes it quite likely that it is PA.

given that % sat is below range may be worth following up on that - though none of your other iron measures look problematic.

If you felt good at 1000 then think that you have probably just been left too long and your levels are now too low for where you need them to be.


Hi swebes it would be good to get your Folate level checked.

There is a complex interaction between folic acid, vitamin B12 and iron. A deficiency of one may be "masked" by excess of another so the three must always be in balance.

Symptoms of a folate deficiency can include:

symptoms related to anaemia

reduced sense of taste


numbness and tingling in the feet and hands

muscle weakness


Folic acid works closely with vitamin B12 in making red blood cells and helps iron function properly in the body.

It is not uncommon for some symptoms to appear to get worse before they get better as the B12 starts repairing the damage done to your nervous system and your brain starts getting multiple messages from part of the body it had "forgotten about" or lost contact with.

I sometimes liken it to a badly tuned radio on which you have turned the volume up high trying to catch the programme you want when all of a sudden the signal comes in loud and clear and the blast nearly deafens you.

A lot will depend on the severity and longevity of your B12 deficiency as to how long before there is no further improvement or recovery.

Some symptoms will "disappear" quite quickly whereas others may take months or even years. There is no set timescale as we are all different.

I am not a medically trained person but I've had P.A. (a form of B12 deficiency) for more than 45 years.

I wish you well



Thanks for chiming in, clivealive.

I had folate checked recently and it was 13.7 (no ref range given). So I think it's good on that front at least.

It would be great if my doctors would respond to messages :) Then, maybe we would get somewhere...ha! Regardless, I'm going to push the issue. Too many of my symptoms line up with this deficiency.

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