I have dub, leg weakness, I take vitamin which has b12:15mcg, b6:40mg, iron:20mg... Been taking it for 1 month. I want to give B12 test. Should I stop vit?

No. Continue the vitamin. The test will show whether the supplement is adequate for your condition or whether it needs to be increased.
Agree with Dr, L. No need to stop taking the medication. If your B12 level has not improved with oral intake, you may need injections of B12.