yes, you can take it whenever you want, except a week or so before getting your wife pregnant or a month before donating blood to others.
And you should take it before and after surgery, even if your Doctor tells you not to. that can be your little secret, and your protection for any weak hairs that might go into shock.
It's natural to be nervous beforehand. I gotta tell you though, I've been on a "high" ever since mine last week. If you did your research, you'll be happy with the results.