Can you use viagra (sildenafil) while on chemotherapy?

Yes, unless . . .: Yes, unless your oncologist (or dispensing pharmacist) tells you not to do so. The fact that you're asking online worries me. Either you didn't tell your oncologist everything that you take (OTC, prescription, dietary supplements, etc) or you don't trust what s/he said. It's imperative that you tell every doc that you see everything that you take. And that we can gain your trust to best help you