Can i take vitamin c while taking antibiotic?

Yes: You don't say which antibiotic but I am unaware of any adverse interactions between vitamin c and any antibiotics. If you are on an antibiotic you have an infection and vit c generally helps our immune system fight infections. I advise 1-2000 mg 2-3x/day for most people with infections. I also recommend probiotics during and after antibioitics, esp. One with scachromyces boulardii like florastar.