Pernicious Anaemia Society
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How long before I see any benefit from my B12 injection ?

I know it's early days yet, [ I had my first injection on Thurs. ]

I was told to go back to my Dr, in 3 months time, but just wondering IF I dont feel any benefit, say after 2 months, should I go back for another blood test, or wait till the full 3 months are up.? My B12 wasn't really low at 226, but thought to be borderline, and I was/am getting all the symptoms of defficiency. Perhaps as I am borderline I may, hopefully only need the one injection ?

16 Replies

Hi Bowler,

In my experience you won't see any benefit unless you get the loading dose of 6 injections over 2 weeks. You have to get your levels up high quickly and then try to keep them there. I would say well done to your doctor for treating you at the low end of normal (not many of them will), but please print this off and go back in to request the loading dose.

The BNF is the book they whip off the shelf and refer to when they're writing out prescriptions. Point out to the doc that it's water soluble so you can't have too much as you'll just pee out the excess.

I've just had the loading dose and some of my symptoms actually intensified initially (particularly the neuro ones), although the fatigue lifted almost straight away. It was only after about the 4th injection that I felt this settle down, and now I'm feeling better than I have done in ages.

One injection would have done nothing for me. My serum B12 was around 300 (higher than yours), I had to have an MMA test done privately to prove I was deficient and receive the right treatment. My GP also tried to give me just one injection but I pointed out the BNF and insisted on the rest.

Your GP sounds like they may be approachable too. Good luck!


Bower from what I remember from 25years ago when I was first diagnosed I had to have two or three injections in quick succession and then only every three months, but I also remember not feeling much difference to start with and each time my injection is due I begin to feel very lethargic just like before I ever started the injections but once I've had my next injection I seem to,pick up quickly. But it is very early days for you and perhaps because you were only borderline deficient the difference will not feel so different to how you usually feel. I don't know if this helps, but if you are concerned go back and speak to the qualified person for them to explain it to you. Wishing you well. I have found Mashby site very interesting and helpful you can go to the directory to find that contributer.



Thank you hampster1 and lightening for your info. I am quite new to this site, and finding it very informative.

Where do I get a MMA test done,? I seem to think that someone else on this site, mentioned St Thomas's in London ? however that would be too far for me as I live on the Cambridge/Suffolk border, Addenbooks hospital in Cambridge is my nearest.

Just one more question Is chest pain another symptom of PA?


Since you've already had an injection this will skew any further tests you have done. Your best bet for now I think is to try and get that loading dose, your GP sounds approachable?

I have autoimmune thyroid disease as well, and it was my (private) Endo who arranged the MMA test for me, at my insistence I might add, had to fight for it.

Here's a good link about getting the Active B12 test / MMA / homocysteine at St Thomas' in London. You could phone them up and discuss the fact that you've had one injection already? You have to pay for the tests (not sure how much) and you need a GP referral letter. Worth speaking to them, as I think they accept samples by post as long as they receive it within 24 hours:

I got fabulous advice from the Pernicious Anaemia Society, worth checking out their website, just reading the forum section "My Story" is a real eye opener...


In addition to my previous answer, this explains why serum B12 is not the best marker of deficiency:

Also you need good levels of folate to get the most out of your B12 injections, do you know what your levels are? Anything low normal needs action, your GP can prescribe 5mg folic acid if you need it.

Finally, make sure your ferrittin (iron stores) and vitamin D levels are good; again low normal results will not be doing you any favours.



I did get some advice from the PA society, last week, and saw my Dr. straight away She read the info I got from the society and gave me the B12 injection. Then just said come back in 3 months,

Some of my blood results

Serum Ferritin 178 should be [ 13-150 ] so a little high.

Serum iron 14 [ 8.8 - 27 ]

Iron binding 59 [ 45 - 72 ]

serum folate 10.04 [4.6 - 18.7 ]

Iron saturation 24% [ 20-40 ]

haemaglobin estimation 143

red blood cell distribution 14.3 [ 11.5 - 14.5 ]

red blood cell count 4.76 [ 3.8- 5.8 ]

TSH level 1.05 [ 0.2-4.2 ]

I dont have any results for vitimin D I do take Calcichew

I have been on long term steroids for Giant Cell Arteritis

I hope I haven't bored you with this info


No of course not, you should see how I bore on about this subject at home!

Are you a member of the PAS (you need to be a member to post on the website)? They're good at interpreting bloods if you start up a topic under My Story. I'm fairly new to all this stuff too. If your GP was reactive to the information from the PAS then I definitely think you should press the issue of the BNF guidelines.

I also take Jarrows B-Right (a good vitamin B complex) and use a Methyl B12 sublingual spray, to keep my levels high now I'm on the 3 monthly injections.

You mention chest pain, do you get palpitations? Do you have a high resting pulse rate? Shortness of breath when you exercise? It might be worth asking your doctor to get full thyroid function tests. This would include TSH, Free T4, and thyroid antibodies test. Your TSH is in the lower end of the range, as it gets towards zero this could indicate HYPERthyroidism. Sometimes people who are Hyper have a high ferritin level which drops when they are treated. I have Graves Disease which is Autoimmune Hyperthyroidism. My ferritin wasn't high, but I know it can be with this condition.

If you hit the "reply to this" button, then I'll get an email saying you've responded. :-)


I'm sorry but it was the B12 site not the PA site that gave me the info re going to my Dr.

The extra vitamins you take Do I get them from the health food shop?

I get a pain/palps that sometimes mimick indigestion, but it's not that, I also get a hot sweat with them. I have a low pulse rate probably because I take a beta blocker for high blood pressure [ I'm falling apart!! ] I'm not short of breath.

I suppose with all these symptoms that are sometimes the same as other diseases it does become confusing, it's like the pins and needles in my hands,legs and feet, someone said that could be vasculitis.?? also I heard that high ferritin levels can go up with inflammation, and Giant cell arteritis is an inflammatory disease, no wonder I'm losing the plot!!!


Gosh yes, you've got a lot going on there. Pins and needles is defo a PA symptom, so you need to get this properly treated and see if it makes a difference to your symptoms. The PAS website is here:


I'm pretty sure that your steroid medication will interfere with B12 absorption, worth googling I think. Would recommend that you read the book "Could It Be B12?" it is a mine of information.

Since you already have an autoimmune condition I really would try and get your GP to do the following:

- Intrinsic factor Antibody (positive in 50% PA sufferers, but you can still have PA and be negative)

- Parietal Cell Antibody (positive in 85-90% PA sufferers, but can be present in other medical conditions)

- Thyroid Antibodies (the one I've had done is TPOAb, there are 2 others I think).

The B12 spray I use is called Boost, think you can get it in Holland and Barrett. There's other brands out there, just make sure the one you get has Methyl B12 in it. I get the B-Right from here:

They also do a high strength sublingual:

But please please go and insist on that loading dose first...


Hello hampster1

I called my surgery today to ask about a loading dose.

I didn't have much luck, and was told that as I was borderline [226 ] The b12 injection I was given was a trial to see how it goes, and to go back in 3 months.


I would make an appointment to actually see the GP face to face. Point out to them that when embarking on B12 treatment the recommended initial dose in the BNF is a loading dose of 6 injections. Perhaps ask them to point you to the guidelines they are following, so that you can put your mind at rest that 1 injection is enough.

You say that your GP gave you the 1 injection off the back of some information from; was it the Treatment Protocol? Because if it was, this clearly states 3 suggested treatment plans on page 7, all of which include loading doses. So you could say that whilst you're pleased that you were listened to and received some treatment, according to the Protocol you actually need more injections before any benefit will be felt.

This is a simplified version of the recommendation which you could give to your GP to read:

Noting the section "Therapeutic Trial". Point out that 1 injection is not enough to assess any clinical benefit, you actually need the full loading dose. If no change has occurred after that then fine, it's something else causing your symptoms. Point out that this is inexpensive and non-toxic and could make a real difference to your life.

Try and bring someone with you as I know from experience it's difficult to say everything you want to say when you have brain fog!

If still no joy then you might have to go down the private testing route for Active B12/MMA/homocysteine, but of course you'll have to wait for that 1 injection to leave your system to get an accurate result. St Thomas' would be able to advise you on this I would imagine.

My heart is so heavy over this kind of stuff, it's only a vitamin for goodness sake, why is is kept under lock and key?


I will print off your info.

I do have the e/mail from the b12 site that I showed my GP, She did read it. I obviously cant send you the e/mail on this site.

I live in a small village, and our surgery is going through some changes. Our 2 GPs [ Man and wife ] are retiring at the end of the month, and haven't been in the surgery much,[ we have been having Locums], however it was my own Dr who I saw re the B12 injection.

I spoke to the nurse re the loading dose,as my Dr. wasn't there, but he only looked at the computer and repeated what she had put on it.

We have had our Drs. for 30 years, seen them come as young Drs. had their family and now retiring, all very unsettling for us all.

By the time I try to get this sorted my Dr will be gone. Perhaps I will wait to see the new Dr.?

I have to have regular b/tests for my ESR which will soon be due, so perhaps I will ask for my "ironwork" to be done again and see if there are any changes, but I dont suppose there will be in such a short time.


Keep us posted on how it all goes, hopefully the fresh eyes of a new doctor will give you some answers. I still think full thyroid function tests would be a good idea, TSH on its own doesn't really give a full picture. And of course you can dazzle them with your B12 knowledge! Take care x


After PA diagnosis I had 3monthly injections for about 18months. My GP was still testing my B12 occasionally but it was still relatively low. She said it should be sky high with injections. By that time I had joined the PA Society and discovered that I should have had a loading regime at the start. I persuaded (not without some difficulty) my GP to give me the loading doses at that point and I have felt somewhat better since, although my symptoms return after 10 weeks not 12. I have started keeping a symptom diary where I tick off daily my main symptoms. Some never go away.

All the best to everyone!


I have been suffering from indigestion for the last 6 months. It started all of a sudden after 8 months of extreme anxiety and not having meals on time. I started passing stool 6 times a day. Bad stool. Then started extreme fatigue, discoloration of skin, significant hair fall from head and other parts. One day I discovered that if I eat meal in only one teaspoon of oil and use almost no spice, then I pass stool only 2 times a day. Also, dairy and wheat does not suit me. I have been sticking to that for the last 6 months. Only veggies, rice and fruit juice. Thats what suits me. Anything else leads to same old problem. But as a result I have lost 10 Kgs. Two months ago I discovered my b12 was significantly low, 199. Vitamin D was very low too. Doc said take 6 injections for b12 and weekly capsules for D and health will improve significantly. My doses are over but my digestion and fatigue has not improved even by 1%. ( I can give my hair and skin 6 months to improve)

Now I believe that my indigestion for 6 months caused depletion of Vitamin B12 and not the opposite. My stomach could not absorb b12 and as a result all these symptoms. My current level of b12 is high as a result of the injections, but it won't last long as long as the root cause is not cured. My GP could not find anything in my gut through endoscopy and biopsy. But indigestion for 6 months means that there is a big problem in my gut but the GP refuses to look further.

Any advice ?


Hey Bowler, how do you feel now? I'm interested to know your B12 story a few years later as I have similar levels to what you reported.

Many thanks!


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