I have an Ileostomy, and P.A does anyone know what percentage of b12 I will absorb
from normal sources, and how often I should inject. I am still getting the stock answer from GP "once every three months" and he will not deviate from this. I have numbness and hand cramps, fatigue, slight balance problems, and leg and foot cramps
It depends on who you believe.
Some people will tell you that you can absorb 1% of an oral dose passively, and 1% of a sublingual dose. So, if you take a 5000 mcg sublingual lozenge then you should be able to absorb almost 100 mcg a day.
Others will tell you that this is nonsense. The body can only absorb B12 if it is attached to Intrinsic Factor, and only in the ileum. You make no IF and you have no ileum, so the amount of B12 you can absorb is nothing.
If you believe the first lot then you don't need injections.
If you believe the second lot then you need injections often enough to keep your symptoms at bay. Obviously this is going to be difficult with your GP. Start off by asking him to treat you according to the updated guidelines in the British National Formulary (BNF). The entry for hydroxocobalamin was changed a year ago, so he is now recommended to dose every two to three months.
If that doesn't work then self-injection might have to be your last resort.
the average absorption outside the ileum is 1% (passive absorption).
Nobody is actually sure how passive absorption works, but it doesn't seem to involve intrinsic factor as it does work for patients with PA (there is at least one study specific to PA) and some literature reviews that have looked at a variety of causes of B12 absorption problems -that show that passive absorption tends to work in something like 65-70% of people regardless of cause of absorption. (I'm afraid I haven't actually been able to re-find the study though I have referenced it on the forum some time ago).
Talking about an average is very different from talking about what will happen in a specific individual, as you will see from the figures about whether passive absorption works some people obviously don't have any significant degree of passive absorption - the reasons for this aren't understood which means that there is no way of knowing if particular individual is going to be able to use passive absorption.
It is worth trying it. clivealive finds that sublinguals work for him and I find that they work for me.
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