What can cause Vitamin B12 deficiency despite Vitamin B12 supplementation?

Someone I know had blood test done, and the results showed Vitamin B12 deficiency. But the said person was already taking Vitamin B12 supplements in high doses.

What type of cobalamin is this person on?

http://www.webmd.com/diet/vitamin-b12-deficiency-symptoms-causes

...

I have a problem with the absorption of b12 (Microscopic Colitis), pills won't do much in my case so I use IM injections.

I'd suggest a B-complex instead. B12 requires B6, but on a broader scale, all the B's function best together.

Do look into methylcobalamin. Everyone should probably avoid cyanocobalamin.

Tomorrow Tomorrow : Have you tried the transdermal behind-the-ear patches?

I use hydroxocobalamin injections (ofcourse methyl and adeno are also good).
Misirlou: I haven't tried the ear patches. I have tried sublingual pills, nasal spray with no effect.
My b12 level last year was so low (50) that injections were/are the best option. I feel so much better now.
I agree that a B complex is beneficial to use together with b12. (I use Thorne's basic B)
MikeGore: this person also needs to check his vitamin D level.

It just says on the bottle, vitamin B12 of type cobalamin 1000mcg. She was also taking Pyridoxal-5-Phosphate 12.5mg

If someone has a b12 deficiency they always have to do further tests to find the cause of the deficiency!
If it is a serious deficiency, b12 pills (no matter what type), sprays or patches won't work.
And take a good b complex instead of only p-5-p.

http://howirecovered.com/understanding-methylation/

http://forums.phoenixrising.me/index.php?entries/methylation-acne-and-hairloss-fredd-and-rich-any-insight.1545/

http://forums.phoenixrising.me/index.php?threads/methylation-hair-loss.11286/

These forums and websites go into great detail of the b vitamins.


"
   Methylation is a central and vital process in the whole body and if this get’s disturbed, all sorts of things go wrong. Mercury is known to disrupt this process.

   There are lots of different supplements that you can take to improve this, but the basic ones are: B vitamin complex, folate and vitamin B12. All of these are recommended by Cutler.

   In my case, B12 acted as a sleeping pill for the first 3-6 months. Really knocked me out, but in a good way.

   There is a great deal of debate about what exact form one should take of these supplements. Many people on FDC, including me, more or less follow the advice of a person called Freddd, that has a very long thread about this at Phoenix Rising and here. What it boils down to is:

   The folate needs to be in active form (Metafolin) and the recommended one is this. BUT for it to work, you must eliminate all non active folate (folic acid). Many normal B complex has this and in the US it is also added to some food.
   One recommended B complex that has only Metafolin is this.

   Finally, the recommended B12 is this and this. Important: These needs to slowly (minimum 40 minutes) dissolve under the lip or tongue.
"