A couple of years ago, I checked out various websites offering Viagra and was very suspicious of most of them. A few seemed genuine, but in the end I went to my GP. The price I pay for private prescriptions seems reasonable, and I have the security of buying from a chemist's shop that I trust. My GP has my health records for the past 35 years, including the results of precautionary checks, not least on my heart and blood pressure.
(Incidentally, is any one fool enough to respond to those tedious spam emails offering Viagra at $1 a tablet/)