Pernicious Anaemia Society
14,242 members10,199 posts

constipation and b12

Hi. looking for some advice as I am quite new to B12 issues. I have stopped taking B12 supplements as GP wants me to stay off for a few months so he can test for PA. Before, I started the B12, I was very constipated and bloated. I started having a high bran for breakfast about the same time as taking the B12. This really seemed to sort my problems out, I assumed it was the bran, but since I have come off the B12 my bloating and constipation is back. I am wondering if low B12 can cause this. I also have lower back pain and achy knees. Also if I go back on the jarrow B12 will this do the same job as injections. thanks for the help

12 Replies

If you do have PA you are more likely to be helped by injections. If it is found that you have the antibodies to the intrinsic factor, this proves that you have PA. BUT even if they do not show up in the blood test you can still have PA. The SYMPTOMS are the most important thing. I have been told by a professor of gastroenterology that as a PA patient, I should assume that I have LOW or NO stomach acid,which they do not treat. This can result im tummy problems like bloating and tummy pain, constipation or diarrhoea. I had this and a water-based probiotic has helped me no end. There are references in professional findings about the symptoms being the most important thing and the fact that PA patents do not always show up as having the antibodies(PA is an autoimmune disease) Some others on this site will be able to give you the links to those papers. I can only wish you all the best.


Thank you for your help.


bloating and bowel problems (both constipation and sudden urges to go) can be associated with B12 deficiency, but they could also be indicative of another underlying problem that is affecting absorption in general.

The back pain and achy knees could also be the same.

It is possible to treat a B12 absorption problem with very high doses of B12 - and the doses in jarrows are the right bracket - 1000-10000mcg. Most B12 is absorbed in the ileum so if something goes wrong there then you lose 99% of your absorption - but sometimes you can use the remaining 1% through the rest of the gut. Though the main intention is absorption through membranes in the mouth rather than looking trying for absorption in the gut.

If you have an absorption problem in the ileum then you will also have lost your ability to store and recycle B12 (stored in liver and recycled by release into the ileum for reabsorption), so if the tablets work then you will need to continue taking them from now on.

Injection is a much more efficient way of getting B12 into the body - with intra-muscular providing a more efficient route than subQ but both can be very effective.

Other possibilties include nasal sprays and skin patches.

It is, of course, up to you as to whether you feel you can live with a period of feeling awful in order to get a proper diagnosis (though even then there is no guarantee a diagnosis will be forthcoming due to problems interpreting results - which is often done on the basis of just looking at the figures rather than looking at clinical presentation).

The upside to a proper diagnosis is that it is on your medical records, though this doesn't guarantee that you will actually get the B12 that you need because the regime is a bit parsimonious (stingy) and makes no allowance for the enormous amount of person variation when it comes to B12.

1 like

Thanks for your help, my GP didn't seem to think there could be any connection in my stomach problems and low B12. He said it was more likely to be IBS and gave me a prescription for that. My TSH levels were elevated as well but he ignored this, and said we should test again in a year. It really is a matter of heal yourself or suffer. Thanks again.



IBS is actually a label for a cluster of symptoms - as is depression - that could have a number of different causes. Sad that GPs aren't as aware of this as they should be so it's treat the symptoms not the cause.

Suggest that you look at the check list of symptoms on the PA website- tick off what is relevant and take that with you to the GP next time you see him - or you could send it through before hand with a covering note.



It is the lack of stomach acid that causes the stomach prblems. Also stomach acid is required along with Intrinsic Factor to extract and absorb vitamin B12. So you can see how it is linked!


Have you ever been investigated for coeliac? There could be a link between your absorption, your low B12, and your bloating/constipation.


Just wondered if you had ever been checked for Coeliac disease? It is possible to still have Coeliac disease with negative blood test result.

"Also if I go back on the jarrow B12 will this do the same job as injections"

My personal opinion, due to my experiences trying to get a diagnosis, is that any form of B12 self treatment can make it very difficult to get a diagnosis from the NHS. See link below.

Thyroid symptoms can overlap with those of b12 deficiency. Have you ever had thryoid tests?

B12 Deficiency Symptoms


See Symptoms checklist.


I have had a test for coeliac disease because my sister has it. The blood test came back normal. I have also had a private test with blue horizon that came back with TSH 4.7. which they said was elevated as their level went up to 4.2. My GP said that was fine and we would retest in a year.


Have you been tested for h pylori? It is another possible cause of low B12 and can have stomach symptoms.



The links I gave in my post above mention that if Coeliac type symptoms continue after a negative Coeliac blood test then GPs can ask for an IgA test.

People who are IgA deficient will not make the normal Coeliac antibodies so the standard Coeliac blood test will probably be negative in IgA deficient people.

People need to eat plenty of gluten in the weeks perhaps months prior to a Coeliac blood test so that plenty of antibodies are produced for the test. If a person who is Coeliac has not eaten much gluten prior to test , the test may come back negative.

I am not a medic just a patient who has struggled to get a diagnosis.

It might be worth you posting about thyroid results on the Thyroid forum on HU. some people can be symptomatic for thyroid problems with results that are within normal range.


It's possible to be gluten-sensitive without being celiac. Last year my 24 year old daughter discovered her acne disappears when stops eating gluten so she is obviously sensitive. There are others who had GI problems which magically clear up after going off gluten even though they tested negative for celiac. My dentist (a woman) and her sister are two others I know about.


You may also like...