Hello All. This may be a naïve question, but I could not find any direct answer to it in previous posts on this site, though possibly I didn't look hard enough. I know all about the need for B12 injections, as opposed to sub-lingual, as I have been doing this for a year now. B12 tablets simply don't work for me. I understand that it is necessary to get round the digestive system, which is not producing B12 and possibly other vitamins: ergo IM injections. My question is: how is it that I can take other things - multi-vits, folate etc - in tablet form and these WILL be absorbed normally? I have read often on this site about the importance of taking these other vitamins in parallel with B12 injections. I presume it is quite acceptable to take these things in tablet form, since I have never heard of folate etc injections? Many thanks in advance for your patience with a complete beginner.
Absorption and all of that... - Pernicious Anaemi...
Absorption and all of that...
I think the short answer is that Vitamin B12 is a unique and difficult vitamin to digest and absorb.
First, there needs to be acidity in the stomach to cleave the B12 away from the protein source that it’s attached to. Second, there needs to be intrinsic factor available to bind to the B12 to allow it to be digested and absorbed much lower down the gut in the ileum.
With PA, both acid and intrinsic factor may not be available.
As I understand it, other vitamins are digested in a much more straight forward process.
All other vitamins are quite small molecules and can pass from the gut into the blood without help (although some, like folate do get some help - like a VIP channel through customs).
But B12 is quite different, especially in its size. It is about 3 times the weight of folic acid. That makes it very difficult indeed for it to cross the gut wall. It needs to be helped across by a protein called Intrinsic Factor (IF).
But, in Pernicious Anaemia the immune system kills the cells in the stomach that make IF. That makes it impossible for the B12 molecule to cross from the gut into the blood.
Great replies that cover B12 deficiency due to PA from the others.
Just to add that some of us who are B12 deficient don't necessarily have PA (although that may be the case as well) and have more general malabsorption problems. In those cases you are right in questioning the absorption of everything - it can be a significant problem. This then also applies to painkillers, hormone tablets and other medicines, etc!
Folic acid and some other things are available as injections and until recently it was possible to get a multivitamin and mineral injection. It was sold in multiuse bottles but the preservative that was used to keep it has been withdrawn and until they can get a new product licenced it is unavailable. As far as I am aware all vitamins and minerals are available for injection for use in intensive care units.
A degree of absorption occurs through the membranes of your mouth and some things, like magnesium, can be absorbed through your skin. Otherwise you have to take very high doses of everything (this MUST be carefully controlled and is NOT recommended without guidance and regular testing as absorption rates can fluctuate and too much is as bad as too little) in the hope that a small % of what you take does get into your system.
Be thankful if you "only" have trouble absorbing B12! 😁
Very useful - thanks Deniseinmilden!
Well ive learned something, as i have always wondered that also. 
Can PA effect the absorption of other vitamins? 
Updated B12 and folate results
OTHER SUPPLEMENTS WITH VITAMIN B?
Continue with monthly injection?
blood results and one mthfr variant - help please 🙏 
