Sick and scared after taking b12 - Pernicious Anaemi...

Pernicious Anaemia Society

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Sick and scared after taking b12


Newbie her and I feel so lost! My gp diagnosed me with pa earlier this week.(220 was my level) She said I needed the shots, which I refused, bc years ago when I took them for weight loss they made me rage and extremely angry and irritable. So I started b12 lozenges two days ago: Hydroxocobalamin 2000 mcg. Yesterday afternoon I felt like death- weak, tired, shallow breathing, and last night tingling in legs and fingers. I thought it could be potassium bc in the past when I’ve gone to er for heart racing, the only thing they’ve ever told me is that my potassium was low. So I’ve been eating avocados, bananas, coconut water. Today I feel worse. Weak pulse, like I can barely feel it in my neck, headache, and nausea. (I did not take the b12 today.) Anyone have any advice? Doc acts like I’m crazy when I say I react to vitamins. I’m scared and don’t know what to do if I can’t take b12 to raise my levels.

17 Replies
clivealiveForum Support

Hi Mcpowell are you in the U.K?

Sorry to be blunt but if you have a definite diagnosis of Pernicious Anaemia and as you say "I can’t take b12 to raise my levels" then you are going to die.

I was told 46 years ago that I was going to die within two years if I didn't have B12 injections for the rest of my life and I'm still "clivealive" and over 75.

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.

If you can get to see a doctor please also ask him/her to check your Folate level as this and B12 help your iron to make red blood cells and to function properly.

I am not a medically trained person but I think you will be better of having the injections rather than the tablets.

I wish you well.


Hi McPowell. I'm so sorry that you feel so ill and scared.

The symptoms you describe above are the symptoms of B12 deficiency, which may be worsening as you become more deficient. Or you could have other deficiencies too (ferritin, folate, vitamin D).

One difficulty of deciding what‘s happening in your case is that when receiving B12 injections, the symptoms of B12 deficiency often get worse when treatment starts (as clivealive says above). This is further complicated by the fact that the listed potential side effects of B12 injections are exactly the same as the symptoms of B12 deficiency.’s not always clear or easy to decide if the apparent worsening of symptoms is due to the 'usual' healing process (things get worse before they get better) or whether it’s due to an actual problem with the B12 itself (either in injection or in other forms).

Two other possibilities for the perceived issues with B12 may be that the injections you had all those years ago may have had quality issues (depends on manufacturer /supplier - quality, injectable grade etc.) or whether you may have a problem with the excipients (the things B12 is mixed with), rather than the B12 itself.

So...where do you go from here...

The first thing is that you do have to find a way to get B12 into your body - as Clivealive says, untreated B12 deficiency (whatever the cause) is fatal. I say this not to scare you but to try and help you understand that simply refusing to have injections is not the way forward (and in the UK, injections are the recommended treatment for those with neurological symptoms due to B12 deficiency).

There are a couple of things you could try...

A) work with your GP and try B12 injections - you may find that you do not react as before (though getting worse before you get better is something to be aware of). After the first injection, your GP will keep you in the surgery for half an hour to ensure that you do not have an extreme allergic reaction. And thereafter, can monitor and review your progress closely.

B) it may be that that smaller doses of injected B12 (0.5mg per injection instead of 1mg) are tolerated more easily if you have problems - something you could discuss with your GP.

It may also be that you can find a different way of taking B12 that your body will tolerate (patches, sublinguals, nasal sprays etc) though it may take time and error before finding something that works, and these don’t work for everyone.

The concern in your case is that you have neurolgical symptoms and these need to be treated effectively as quickly as possible...and injections is the best way to do this.

It really is important that you go back to your GP and talk about how the both of you are going to get B12 into your body - cause it's your GP's responsibility to help this to happen if your body does have an issue tolerating B12.

If you try the injections under your GP's supervision and still experience problems, there are two consultants in London who specialise in treating those who are allergic to B12 - your GP can (and should) take advice from or refer you to either one of these specialists if you cannot tolerate B12 injections.

These specialists can desensitise those with allergies to B12 so that B12 replacement injections are tolerated.

Names and emails of the two consultants can be obtained from the Pernicious Anaemia Society's Website (you may have to be a member to access):


I understand that both of these consultants respond to emails from GP's who request help, something you GP could do if they need advice about how to help you.

Alternately (and if you GP does not realise that allergy to B12 can exist), your GP can telephone Martyn Hooper, the Executive Chair of the PAS (address on website link above) and he can give further advice and guidance about this.

If your GP is resistant to helping you (many are not well informed about PA), or you feel you can't deal with this alone, then please consider joining the Pernicious Anaemia Society - Martyn Hooper can intercede with your GP, on your behalf, if necessary.

So, though it's scary for you at the moment, there are things that can be done to get B12 into your system, and it’s really important that this happens, and happens quickly (because of your neurolgical symptoms).

So, please do go back to your GP and discuss your fears about the possibility of a B12 allergy (rather than a reaction to all vitamins) because B12 allergy does exist (although it is quite rare). Point them in the direction of the Pernicious Anaemia Society and be prepared to try B12 injections again if your GP suggests this - you may find that you don't experience the problems you had before.

And if you do, your GP will have 'evidence' and can take specialist advice on how to treat you so that you can then receive B12 injections.

Good luck. Let us know how you get on 👍

P.s. low levels or deficiencies in ferritin (iron deficiency anaemia), folate and vitamin D often go hand-in-hand with PA and can make you feel very ill indeed (symptoms are like those of B12 deficiency). Hope your GP tested these too 😉

Mcpowell in reply to Foggyme

Thank you for the response. This is all so overwhelming. Since the time I posted, I went to emergency room. My potassium was low so they gave me some magnesium in an iv and potassium pills. Unfortunately, I threw up once I got home so not sure it did any good. I’m not sure why my potassium drops with b12 supplementation. clivealive thank you also. I appreciate it any advice.

clivealiveForum Support in reply to Mcpowell

Have you perhaps been "overdoing" the potassium in the past?

I'm sorry I was a bit blunt with my response last night.

I well remember how Zombie like I was back in 1972 when I eventually was given the P.A. diagnosis and told I either had to eat raw liver, three times a day, or B12 injections for life. I chose the injections :)

Please take note of the excellent advice Foggyme has given you and I hope you soon get the treatment you need most suited to you.

Mcpowell in reply to clivealive

No worries. I’ve never taken a potassium pill in my life until yesterday in the er. I’ve only brought levels up in the past through food sources: coconut water, bananas, potatoes and avocados.

Thanks for the article. I’ve been reading on a CFS forum and I just need to figure out how to get b12 without depleting potassium, but first I have to understand why it happens in the first place. Methylation is a complex subject for me, but I think it the whole mthfr mutation comes into play. I’m thinking some issues with adrenal glands might also come into play.

Gambit62Administrator in reply to Mcpowell

if you had macrocytosis - red blood cells larger and rounder than normal - then the body can start using slightly more potassium when this is corrected resulting in a drop in potassium levels - it is a possible side effect of starting B12 treatment and monitoring for it is one of the many suggestions in the guidelines in the UK but guessing that you are based in the US

Mcpowell in reply to Gambit62

Yes I am in the US. I didn’t even realize this site was based in the UK until yesterday. 😬 It has not been mentioned at all, so I feel alone in my quest for answers. Finding good care is hard. I called my gp yesterday from er and still haven’t heard a call back. Thanks I will look into macrocytosis!

FoggymeAdministrator in reply to Mcpowell

Hi Mcpowell. Sorry to hear you had to visit the ER but good to hear that your low,potassium has been dealt with.

As per Gambit's explanation, when B12 therapy is first commenced, potassium is used in higher amounts to help repair macrocytosis (enlarged red blood cells - if they are present). In those with good levels of potassium, this is not a problem but where potassium levels are already low, then the body's extra initial requirement for,potassium causes potassium levels to become too low...and this causes the type of problem you experienced. (The initial need for additional requirement lessens once the macrocytosis has resolved and thereafter a diet rich in potassium is usually sufficient to maintain appropriate levels - though your doctor can keep an eye on levels and re-prescribe potsssium tablets, if required).

This may (or may not) explain why you have reacted badly to B12 injections in the past...the issue could be low potassium rather than an allergic reaction to the B12 itself.

In the UK, guidelines state that potassium levels should be checked early in the commencement of injections (24 hours, I think)...though not many GP's do this. Sadly.

The fact that you had to go to ER and have been given potassium tablets should help with this situation and may mean that you can take B12 injections without the bad reaction you experienced in the past. It also means that you have the 'evidence', to reasonably ask you health care practitioner to periodically check your potassium levels, especially if you commence B12 injection....which is what you would be best to aim for.

If you discover that you indeed have an allergy to vitamin B12, then your health provider in the USA could perhaps find a specialist who deals with desensitisation. Or they could email either of the two specialists for further advise.

The quest for answers is as lonely in the UK as it is in the US - unfortunately 😖. You're more than welcome to post questions in the forum so that we can try and support you and help you feel less lonely.

Where we talk of guidelines about the treatment of PA, these references are to UK treatment guidelines. But the information about PA and B12 deficiency in general is relevant anywhere in the world...and we do have members from across the globe.

I'm going to post some links below that will give you more information information about PA, serum B12 testing, some of the common mistakes GP's make etc. so that you can become better informed about PA - and what doctors should be doing to help you. Most here find that becoming well informed and then passing this information to their doctors does hopefully it may help you too.

There are quite a lot of links (to go along with Sleepybunny's) but most are only one page long, and will help you to be well-informed when you approach your doctor.

The first link is to a B12 treatment review written by an American Consultant Haematologist, so would,probably a good one if you want something to share with your GP: (Haematologist B12 Treatment Review March 2017 – Includes Advice No Reason to Advise Against Self-Injection/More Frequent B12 Injections)

And here's the rest, for general information:

b12researchgroup.wordpress.... (Serious Caution Note about the use of Oral and Sublingual B12 Supplements)

(BNF B12 Deficiency: Hydroxocobalamin Treatment Regimes)

pernicious-anaemia-society.... (PAS Symptom Checklist) (BSH B12 Deficiency / PA Diagnostic Flowchart) in Haematology (BSH) Guidelines: Treatment of B12 Deficiency and Folate Disorders) (UKNEQAS B12 Treatment Alert, Neurological Symptoms and Risk of Subacute Combined Degeneration of the Spinal Cord – Immediate Treatment with B12 Injections) (Problems with Serum B12 Test) (Testing B12 During Treatment) (Misconceptions About B12 Deficiency – Good to Know Before Seeing GP) (B12 Deficiency: Neurological Symptoms Can Present Even When B12 is ‘In-Range’ and Without Macrocytosis (large red blood cells) or confirmed PA Diagnosis) (B12 Deficiency and Intrinsic Factor – Can Be Negative and Still Have PA) (B12 Treatment Safety / Long Term Treatment for neurological symptoms) (B12 Deficiency and Neuropsychiatric Symptoms) (Low B12 - Nitrous Oxide Contraindications) (Gastric Autoimmunity: Heliobactor Pylori)

Good luck and post again if you have any more questions, need further advice, or just want a few warm words from out ,overly forum members.

Take care 👍

Mcpowell in reply to Foggyme

Thank you so much!


I'm not medically trained.

Might be worth joining and talking to PAS soon. If you join PAS , you can access details of PAS support groups in UK.

PAS (Pernicious Anaemia Society)

Based in Wales, UK.


PAS tel no +44 (0)1656 769717 answerphone so messages can be left

PAS support groups in UK


I've written some detailed replies on threads recently, may be useful info if you search for them. More B12 info in pinned posts on this forum.

B12 Deficiency Info website

B12 books I found useful

"What You Need to Know About Pernicious Anaemia and B12 Deficiency" by Martyn Hooper

Martyn Hooper is the chair of PAS (Pernicious Anaemia Society). Book is up to date with UK b12 guidelines.

"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 with lots of case studies.

UK B12 documents

BSH Cobalamin and Folate Guidelines

Flowchart from BSH Cobalamin and Folate Guidelines

BMJ B12 article



Hope you get the help you need.

Mcpowell in reply to Sleepybunny

Wow very helpful, thank you!!

Sleepybunny in reply to Mcpowell

USA B12 website

Some info in my post above is UK specific. PAS has members from around the world.

More B12 info in pinned posts on this forum.

Macrocytosis (UK link, some info may be specific to UK)

Complete Blood Count (known as Full Blood Count in UK)

Blood film/blood smear

I had no detectable b12 when my levels were finally checked. I was a total wreck in every way what with my whole nervous system dying. Every symptom imaginable. I can tell you I started with one shot a day for a month, then 2 shots a week for a month, then 1 shot a week for a month and then one shot a month. I never experienced any set backs, no extra side effects, no negative experience from taking the shots. Only thing I had was slow steady healing. Doctors have used B12 shots as placebos for years. A B12 shot will do nothing for you unless you are low on B12 and then it is not immediately, and it would take more than one shot. Your body flushes any B12 it does not need. It stores what it does need in the liver. Nerve damage and blood disorders low B12 causes take a while to get better.

Hello Mcpowell, I have enlarged red blood cells and am taking Jarrows sublingural B12's I nose dived to the ground like you when I first started taking them. I felt much better for 3 days and then crashed! I had low potassium problems and unfortunately low salt goes hand in hand with that too, and both were on the ground. Rapid racing heavy beating heart rate sent me to E.R. Not to mention the scared and anxiety when your body and brain are so out of wack! I upped potassium and started to take an 1/8th of a teaspoon of seasalt 3 times a day and started within a couple of hours to feel better, I did not realise I had been living with long term dehydration. I am slowly upping my water intake because to go too fast is not good either, I up it by half a glass every day to get to the maxiumum water intake for my body weight. I have been diagnosed with ME/CFS rather than them looking at the real problems. I am also hypothyroid and was and still is undermedicated for that...sending you (((hugs))) xX

So sorry you had to deal with this, it’s miserable!! I tried the adrenal cocktail today with Himalayan salt, as I noticed on my blood work sodium was also low. Can I ask when you resumed the b12 after your crash. I need it as mine is so low but not sure how long I need to up my potassium before I begin. This is all such a delicate balance.

Hello Mcpowell I did not stop the B12 and I kept upping it slowly. I take the Jarrows disolve under the tongue 5000mcg 3 times a day. I started on 1 a day but did not notice a difference until I went up to 2 a day. I had to slowly up my salt and water intake too and I made sure I ate plenty of avocado's and coconut water for potassium. I did not realise my adrenals were knocked out too. My cortisol was low in the mornings rising to high at night when they should be the other way round. I still have a long way to go.

What I experienced was like a healing crises when first starting B12 everything got worse before it started to get better. My feet were so numb but in a couple of days they were in such pain it felt like I was walking on my bare bones. Apparently as nerve sensations start to come back the brain interpretes it as pain.

I enclose a link explaining this darling

Hi Mcpowell,

I hope you are feeling better now. Even though it was posted a month ago I just read your message. I wanted to let you know that I react to B12 shots. I think it is somewhat rare, but it does happen.

Here's my story, I started loading doses about a year and a half ago. One shot a week for six weeks. I felt great, but my blood pressure went up each time I had my shot. The nurse who was giving me my shots was very concerned, but my doctor said B12 couldn't be causing my blood pressure to rise. After my loading doses I started having one shot a month. Everything was going well except my face was very flushed and hot and I had trouble sleeping the night I received my B12 shot.

I decided, for convenience, to start self injecting last August. Because I felt so good after my shots I started injecting weekly for about 4 weeks. The last self injection created a horrible reaction. My face turned bright red, it was very hot, and my nose itched. I had an excruciating headache, my heart was beating very hard, my stomach hurt and I had bad insomnia for three nights. The symptoms started to die down after about a week so I thought maybe it was just stress or something else. I waited a month to have my next injection and I went to my doctor for this one. I told him about my reaction the previous month and he assured me it couldn't have been the B12. As soon as he gave me my B12 shot, my head started to hurt and within an hour all of the symptoms I had experienced the previous month returned. This time I called my doctor right away and told him what was happening. He told me to come in and he would see what was going on. Once again he told me it couldn't be caused by B12 and it must be something else happening. He drew a lot of blood and ran tests but nothing showed up as abnormal.

I started doing my own investigating and I found a small blurb on line from a doctor who said he had had a patient with my symptoms but he was able to treat his patient with antihistamines. So, I took a benedryl before my next shot and continued to take them for about a week. I was feeling pretty good and was able to sleep, unless I forgot to take the antihistamine. If I did forgot the reaction started back up.

While I was happy to have found such an easy solution to my problem, I wanted to delve further into what was causing my problem. I recently found some information online which leads me to believe I have histamine intolerance. My research shows that some people don't produce enough of a chemical called DAO. This chemical is produced by your body to inhibit production and dispose of excess histamine. I have added some food and supplements to my diet to enhance my body's ability to produce DAO and thereby decrease my reaction to outside sources of histamine. I have started to drink a lot more water. Water helps wash out histamine. Olive oil and beets help your body create DAO so I now I have replaced butter with olive oil when I cook and I eat a beet a day. I have started taking an olive leave capsule in the morning and in the evening. Vitamin C is a natural antihistamine so I take a vitamin C capsule once a day. Apples have a natural antihistamine called quercetin so I try to eat an apple a day. I have also given up some foods that cause histamine reactions in the body, wine, chocolate, fermented foods, and kombucha.

Even though I only started this program a month ago, my last B12 shot was pretty anticlimactic. I did take two benedryl the day of my shot but I relied on the rest of my protocol after that and it seems to have worked. I felt fine, actually, I feel great. I think I have been suffering from histamine intolerance for quite sometime.

I know this is an extremely long message, sorry for that, but I hope it helps you.

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