I have my vitamin B12 in a low level at 150, is it dangerous and what should I do to increase it. And does the lack of this vitamin slow the metabolisme?

Low Vit B12. Low vit B12 (vit B12 deficiency) usually at levels below 200, and reportedly at levels below 400 may lead to permanent neurological damage. It is easily treated with once monthly injections or by over the counter supplementation with the subligunal form being preferred. The quality of the lab testing & other factors may lead to falsely low results.