Originally Posted by mrsD

Cyano is just not effective for everyone. Historically it is the
first B12 that can be given to correct pernicious anemia.

But since then, much more has been learned.
People can fail to convert it in the body to its active form, methylcobalamin. This is called methylation failure and can be tested for it you want. MTHFR mutation. This also affects the methylation of folic acid to methylfolate. People with this genetic error end up with high homocysteine levels and early cardiovascular disease.

Why take an outdated synthetic version of a vitamin when its active form is available in very inexpensive form?

When people end up with low B12 activity/levels, it is due to 2 basic things.
1)Failure to absorb the minute amounts in food (called malabsorption, or pernicious anemia).

2) Failure to methylate the vitamin so the tissues can use it.

People end up on internet health boards because some is going wrong in their bodies. Today, you can get tested for
the MTHFR DNA mutation without a doctor's order. It is OTC and costs about $125-150. You can choose to do that, and if you don't have this problem, then cyano may be okay for you.
Its not like the methyl version is soooo expensive...to preclude using it. It is only pennies a day and does not require injection.