When to retest B12/folate/ferritin le... - Pernicious Anaemi...

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When to retest B12/folate/ferritin levels post-supplementation?


Hi all - I spoke to a Dr today about when to get my B12, folate and ferritin re-tested. She said, given I am on an iron supplement, my ferritin levels should be tested in 4 months but that B12 isn't usually re-tested until 6 months post-loading injections. Is this accurate in your experience?

She also said it wasn't possible to request the specific blood test that distinguishes active from inactive B12...but knowing how vague and potentially inaccurate the total serum B12 level test is, this seems crazy to me? Do I really not have the right to request this particular test or is she just trying to fob me off again? (I'm in the UK, incidentally).

Still feeling pretty foggy and listless with my head feeling like it weighs a tonne most days. Dr said I probably won't feel better until at least 6-8 weeks after loading doses/starting iron tablets. Hope she's telling the truth!

12 Replies
clivealiveForum Support

Hi Gilly27 How many loading doses are scheduled and then what frequency? Do you know what your Folate level is?

in reply to clivealive

Hi again! I had 5 shots over two weeks and they finished last Wednesday. My follow up injections are scheduled for every 3 months - so I would have had one top-up before getting retested (just before my 2nd top-up, I believe).

My folate level was 5.3 (3.10-20.5) so at the lower end of normal.

(B12 was 135, 187-883: Ferritin 22, 22-275)

clivealiveForum Support
in reply to Gilly27

Hi Gilly27 if you are still suffering neurological symptoms then your loading doses should have continued "until there is no further improvement" according to both the N.I.C.E and B.N.F. guidelines on treatment for B12 deficiency.


Click on the link above, then on "Scenario Management" and scroll down.

You might think to mention this to your nurse/doctor.

Also you Folate is on the low side and may need supplementing.

As for testing your B12 as Hidden says there is little point whilst you are having injections - unless it comes out very low.

Do you have any idea of the cause of your deficiency? Diet, surgery, medications, other diseases etc?

in reply to clivealive

Hi CliveAlive, sorry for the long delay- life got the better of me for a while!

I spoke to my GP about possible neurological problems I've been having including memory issues (primarily with names and words but also details of past events etc) and irritability/depression (I've been on the highest dose of Citalopram for years) but my concerns were completely disregarded. They really don't like the idea of more frequent injections do they!

I'm now hoping that I will somehow be able to get the MMA and homocysteine test (either with or without the Active B12 test) to better understand my current situation. I'm going to wait 3 months after my first top-up injection and then request these tests (or go private if necessary).

As to the cause of the B12 deficiency and low iron, I honestly haven't a clue! I am not a vegetation by any means and both the parietal cell and intrinsic factor tests came back normal. As did the Coeliac test. I don't take any medications that would suppress B12 as far as I'm aware - except maybe the combined pill. But would that account for my relatively low iron? I don't know..I'd really like some more investigation into the cause of the deficiency, I can only hope that my GP will eventually refer me if I bring it up enough..

Incidentally, I am currently supplementing B12 (injections), Iron (prescription tablets) and Folic Acid (OTC).

Many thanks!

clivealiveForum Support
in reply to Gilly27

I believe certain contraceptive pills can have an affect on B12 levels but as I say I'm not a medically trained person.

I wish you well and hope that you see some real improvement now.

HiddenThis reply has been deleted
in reply to Hidden

In a nutshell, yes. I do not feel better (yet). I want the active B12 test precisely because I am prepared for my total serum levels to be high. I want to know how much of that I can actually utilise. And, if it's not as high as predicted I can use that evidence as leverage to get more frequent injections or to be referred for further investigation as to the actual cause of the deficiency.

When supplemented, iron levels can quite easily increase to the point of toxicity so they are monitored as a matter of course - at least, according to every GP I've spoken to.


active B12 is unlikely to do anything but mirror the results of serum B12. It is not generally availabe on the NHS. Although it is measuring the B12 bound to the protein that passes into cells - rather than the protein that allows it to be stored in your liver - it is still only measuring the amounts of B12 in your blood and isn't providing a guide as to what is going on at the cell level - tests that can do this are MMA and homocysteine - both will be raised if B12 is low. homocysteine will also be raised if folate is low. MMA will be raised by other factors as well. Unfortunately neither test is currently generally available on the NHS.

"Hi again! I had 5 shots over two weeks and they finished last Wednesday. My follow up injections are scheduled for every 3 months"

The BNF (British National Formulary) is a book every UK GP will have access to..probably a copy sitting on their desk or bookshelf. It's also possible to get your own copy and a good library will have a copy in reference section. Relevant info is in Chapter 9 Section 1.2

BNF specifies 6 shots over two weeks not 5.....then injections every 3 months for B12 deficiency without neuro problems

If a patient has neuro problems then treatment is more intensive, injections every other days then once improvement has stopped it's a maintenance injection every 2 months

Have you got neurological symptoms? eg tingling, pins and needles, tinnitus, balance issues, memory problems plus many others

Lists of B12 Deficiency Symptoms




Link below has UK B12 treatment info


UK treatment info also in BSH Cobalamin and Folate Guidelines, about a quarter through document


Flowchart from BSH Cobalamin guidelines


The fact that you have been given 5 shots not 6 makes me suspect that your surgery is following local area NHS B12 deficiency guidelines rather than BNF or BSH . Some of these local area B12 guidelines have not been updated for years.

Might be worth you trying to track down local B12 deficiency guidelines for your area/county.

These UK local B12 guidelines can be tracked down by

1) an internet search

2) search on local area NHS website, possibly under haematology guidelines/policies

3) FOI (Freedom of Information) request to local area NHS website

4) CCG may be able to tell what guidelines are being used in the area


5) Practice manager of GP surgery may be able to tell what b12 guidelines practice is using

6) If all else fails then MP may be able to help track them down


B12 book

Martyn Hooper's book "What You Need to Know About Pernicious Anaemia and Vitamin B12 Deficiency " mentions UK B12 treatment guidelines, I gave a copy of this to my GPs.

Unhappy with treatment?

Link about writing letters to Gps about B12 deficiency. Point 1 is about undertreatment of neurological symptoms.




HDA patient care trust

UK charity that offers free second opinions on medical diagnoses and treatment.


B12 blog posts that may be of interest





I am not medically trained , just a person who has struggled to get a diagnosis.

Risk factors for PA and B12 deficiency




"both the parietal cell and intrinsic factor tests came back normal"

Flowchart below outlines when PA or Antibody Negative PA can be diagnosed in UK.


Other b12 books

I mentioned "What You Need to Know About Pernicious Anaemia and Vitamin B12 Deficiency" by Martyn Hooper above.


"Living with Pernicious Anaemia and Vitamin B12 deficiency" by Martyn Hooper. Has several case studies.

"Could it Be B12; An Epidemic of Misdiagnoses" by Sally Pacholok and JJ. Stuart (USA authors)

Very comprehensive book about B12 deficiency with lots of case studies.

You'd be better off knowing your ( RDW )blood cell width distribution , know that and then you can request to have your vitb12 more often if that is above or below range , it's surprising how the RDW plays a part in vitb12 😊 good luck

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