Hi Mishe, Most people do not react in any way to a b-complex. Generally it does exactly what is expected, nothing noticeable. When cell formation actually starts up it can deplete things, especially potassium and Metafolin but that cam also include any combination of up to 40 or so items,. That is why one needs to take the basics. A 1000mcg mb12 sublingual of one of the 5 star brands can put 150-250mcg into blood serum. While this in not much it is more than is transported in the active transport system and is available to cells throughout the body for healing via diffusion much more quickly so healing starts faster and proceeds faster. There is a clear dose proportionate healing with mb12. If you want to wait on the adb12 a few days go ahead. However that will prolong startup and delay certain kinds of healing and functioning, for instance getting rid of brainfog, return of energy, reducing muscle pain and increase healing. An intensification of symptoms with mb12 is not a BAD reaction. It is the summation of 600 or so processes starting up. However, folic acid can definitely cause a "bad" reaction. I know of no way at all to start them up without the effects of them starting up. You can either get it over with in a few days to a few months or you can stretch it out for months to years or the rest of your life. I've been through all of this from a terribly degenerated condition near death to good health. The things that react first with the startup are often the quickest things to heal. Methylb12 with Metafolin starts up methylation almost right away. It also starts up all the other things mb12 does very quickly.