Cyano and methyl are equivalent in dose orally.

However if you have the MTHFR mutation, cyano will not become biologically active in the body. Only methylcobalamin is active of the two.
If you have the mutation and take cyano you may test "normal" and in fact be deficient. The tests do not discriminate between the two forms.

Studies have shown that 1mg of B12 orally will yield around 13mcg in the blood. This was tested in volunteers.

The injection of 1000mcg yield about 145mcg the same way.
http://www.ncbi.nlm.nih.gov/pmc/arti...able/T1/#TF1-4
Injections are given once a month usually, and the B12 leaves the blood in 72 hrs. We are used to daily intake, so many people get deficiency symptoms waiting for the next shot.
The high mg absorbed from the shot may be lost in the urine and the rest of the month you have none. So daily oral is more reliable.

Not all of a dose is used or absorbed by far.

In people who come here, most have problems with injection not raising blood levels well. They do better on oral used daily however.

If you do not have the mutation, cyano will work for you.
However most people who show up here, and get the testing do have the mutation...this is why they don't heal right and have nerve damage to discuss here. It may be the same here on TBI as it is on PN.