I have in the past.
I cannot in Australia. According to their current guidelines, you can give if you have diabetes (controlled), clear of cancer for a number of years and other ailments(some are restricted), but if you have ever once shot a drug that wasn't prescribed by a registered medical practitioner, you aren't eligible, ever. For me, that was somewhere in the neighborhood of 2 decades ago, but basically if I'm going to follow their guidelines, I can't. Seems discriminatory and over cautious to me especially considering who they do allow to donate. But, whatever.