Pernicious Anaemia Society
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Hi there.

I have Crohn's disease and have difficulty absorbing vitamins and minerals.

I have deteriorated to the stage that I have hypocalciemia, low vitamin D, folic acid , iron and pernicious anaemia.

I've lived for months with chronic pain and fatigue but am looking forward to seeing an improvement after injections and supplements start.

I'm due to get three B12 injections a week starting tomorrow. And have started supplements for the other deficiencies.

Can anyone tell me what to expect after the injections i.e. Common side effects.

I'd like to hear other people's experiences .

Kind regards


12 Replies

Do you mean that you have PA or that you are B12 deficient? - just to be confusing doctors can often mix up the terms but strictly speaking PA is an auto-immune response that stops you absorbing B12 and leads to a B12 deficiency ... and the symptoms of PA are the symptoms of the B12 deficiency it causes. PA is one cause of B12 deficiency - the general absorption problems caused by Crohn's are another cause.

metabolisation of B12 is a very personal thing.

You might find it useful to make a list of symptoms you have that (probably) relate to B12 - but they could be other minerals and vitamin deficiencies but at least it is a starting point

list of symptoms here


monitor what you feel against the symptoms. you can probably expect to feel more energy relatively quickly. you might notice that pains seem to increase a little for a while - you might find that colds start to express themselves in terms of runny noses when you haven't had one for ages.

spots are quite common - rarely this can be very bad - acne type reaction - which may be your immune system kicking back in or it could be that the bacteria on your skin are reacting to the B12 by producing something that your skin reacts to. For most people this quietens down but for a few it unfortunately doesn't.

Some people experience heightened anxiety for a little while - some find the B12 completely wipes them out for 24 hours.

Hope this hasn't scared you. Reality is lots of people don't really notice much for a while.

Even those who do have bad reactions often think it's worth it compared to the symptoms they have suffered ... and the reality is that left untreated a B12 deficiency will kill you and it won't be a pleasant way to go.


I have just been told I have pernicious anemia which has caused the B12 deficiency. Crohn's can sometimes cause malabsorption of vitamins and minerals and lead to deficiencies as in my case.

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No it's not scared me , I'm in chronic pain everyday anyway. I've also got pneumonia ATM . I'm on azathioprine- -an immunosuppressant for my Crohn's disease so a runny nose won't bother me.

I was just st kinda wondering what to expect so I can prepare a bit.

I'm looking forward to eventually haveing a bit more energy and being able to get back into my workshop again 👍. Thank you all for your kind advice

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Hi Pagannana - everything which Gambit62 has so ably said plus please don't take too many folic acid for a couple of days until after the first B12 injection.


Can I ask why that is clivealive ? I started the folic acid yesterday so will only have had two doses before the B12 injection.


With Folate in some countries being mandatorily added to foodstuffs like flour & cereals etc there is a danger that high levels will mask the detection of B12 Deficiency.

This is not important in your case as you already have a P.A. diagnosis and it is unlikely you have raised your folate level high enough with just two doses to exacerbate the effects of your B12 Deficiency.

A healthy level of Folate is essential whilst you are having the B12 injections and gets "used up" during the process.

I've been taking 1 – Folic Acid 400μg every day for more years than I can remember and that's in addition to what is to be found in vegetables etc but then I've been having B12 injections for 45 years for P.A.

I wish you well and hope you soon feel the benefits of the B12.


It's so good you are having treatment - things will only get better. I was diagnosed with Crohns over 43 years ago when I was 27.

It has taken me years to sort out my health and only started B12 injections just over 3 years ago. Too little too late methinks but lots of good things happening too.

I also have Hashimotos. Low VitD often accompanies Crohns and Low B12. I would have it tested. It is an anti-inflammatory steroidal pre-hormone so much more than a vitamin.


Hi Marz

I was only diagnosed with Crohn's just about 4 years ago. At the same time as having a hysterectomy.

I can't imagine having it 43 years with hashimotos on too. I bet you are on a fair amount of medication.

yes I've got very low vit D too and just tarted supplements for that too but may need infusions. I've had to work out a schedule as I'm taking so much medication now on top of what I was already taking. (34 individual tablets+ liquid meds daily + injections thrice weekly) I'm not boasting- just amazed that it's come to this at 50yr old lol.

I get my thyroid checked regularly and ( touch wood) as my mum had is a history of thyroid cancer. Everything ok so far tho 👍.

Sending you all best wishes x


Sorry to read about your meds. Must make you feel poorly.

I had ileo-caecal TB when the Crohns was also discovered. Took medication in the beginning and other times but I resisted as I akways felt more ill. 😊 Had several ops with complications.

All I take now is T3 for my thyroid and loads of supplements. I am gluten free and know what suits me food wise with the occasional slip up.

Have been on the Thyroid Forum here on HU for over 4 years and know that often only the TSH is tested which tells you so little. You also need the FT4 and FT3 tested along with the anti-bodies. Do you have any results you could share ? You are entitled to have copies of all your results legally.

Click onto my name above and have a read about my journey 😊

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Oh my goodness you have had some journey too.

Im hoping once all supplements etc are starting to help me that I can reduce my painkillers. I can't really see what else I can reduce but I'll deal with that when the time comes.

I just feel good knowing that I'm finally getting help. No exaggeration but Some days I felt I was dying I was so sore and weak. Having this chest infection ATM doesn't help but it will pass 👍

I'm with you on the Crohn's meds. I'm on azathriopine which is an immunosuppressant, I catch every bloody thing going and if my grandkids r Ill I've got to stay away from them which is the hardest bit. My Crohn's is too unstable ATM otherwise I'd be stopping them but again hopefully my body will grow stronger and I'll be able to stop them too.

I get my first B12 injection today so onwards n upwards . I'm not sure how it will affect me, I'll deal with any side effects as they happen.

I appreciate you taking time to talk to me, it's very reassuring. Getting told you have any long term ,life limiting illness is horrible and the nhs support is non existent. 😊 thank you.


Really hope the injection goes well for you. Have you been told about the effect of lowered potassium. I usually eat a banana after my injection ! Also it is important to know your Folate levels as the B9 and B12 work together in the body. Keeping all the B's in balance with a GOOD B complex will also give you the B9/Folic Acid/Folate you need.

Would love to see your thyroid results - do you have them ? The Active thyroid hormone is T3. The brain has the most receptors for T3 and the lining of the gut/immune system has the second highest demand for T3 with loads of receptors. So - when the FT3 is low then things do begin to go wrong.

After a lifetime of poorliness the Thyroid issue was the missing link. There are 300 symtpoms that can be linked to the Thyroid. T3 is needed in every one of the trillions and trillions and cells in the body ..... Crohns is auto-immune - as is PA and Hashimotos.


I don't have any of my results I'm afraid. I read them off the computer screen at drs. And I been told bout eating a banana after injections coz o the potassium.

ATM I'm just letting everything sink in . To have one autoimmune disease was not good but now I've got two plus all the deficiencies. I feel hopeful tho that my health will improve and I can start to live again.

Both my parents passed away in march and I had been caring for them as mum had progressive Supra nuclear palsy. A horrible disease that wastes muscles and causes respiratory failure. Dad had copd, congestive heart failure and cancer.

I was devastated when they passed within 21 days after each other and developed a condition called complicated grief syndrome. I was at rock bottom and couldn't function. Deep depression, anxiety, Joint muscle and bone pain, headaches. Vivid dreams etc .

I own my own craft buisiness and haven't been able to work for last couple o months due to pain, fatigue and depression. I really thought I was for the scrap heap.

I think the treatment I've been on for that plus my mental state have masked the symptoms of the PA and other deficiencies.

It sounds daft but for the first time in over a year I feel some hope. Hope that I'm going to get my life back and be able to work again and enjoy taking my grandkids out n get in my workshop 💕🤗

Thank you again for chatting with me . It is very reassuring

Kind regards


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