If the supplements are fiber containing... I'd not take them.

If they dissolve well, it is okay. Fiber specifically absorbs the B12 like a sponge and prevents absorption.

Calcium and magnesium are also suspect because some studies show they interfere with thyroid hormone. Calcium is divalent and tends to complex things into insoluble form...so I don't know if it would do the same to the B12. Until we get that new promised enhanced absorbable one I think being very careful is best. If you have intact intrinsic factor, this situation is less critical as the intrinsic factor will combine with the B12 in the stomach and enable absorption of it. But when people come here with LOW test results one has to assume that things are not working well for some reason. So prudence should be practiced for success. Now if you take your B12 a specific way and get tested in 6mos and show good levels, then that is the way for YOU... testing is the only way to show what is working the best for you.

For example my doctor expected much higher Vit D levels for me, based on my intake. And they were not there! (for whatever reason). Testing revealed that.