I did the research quite a while ago (like 2 summers ago, I think) after reading an article about it on xojane dot com -- certainly not a reliable source, but it prompted me to do my own research. As I said, that was quite a while ago, so I don't remember the reliable sources that convinced me to try it. But I also read really encouraging reviews on amazon, which is where I bought mine. I wouldn't feel comfortable recommending a particular dosage without re-doing that old research. It takes a while for the zits that are brewing in your skin to develop and heal, but I'd say that when I first started using it it was maybe 2-4 weeks before new ones stopped forming (though the in-progress ones still had to run their course). But that's just me.
I started this thread because I just recently started taking it again. Last year I had great improvement from taking Borage Oil, and then when I was getting ready to move in the summer I stopped replacing my used up products so I wouldn't have to drag them cross country with me. Borage Oil was something that I just forgot to start buying again after moving. I can be a real dummy sometimes -- lol! Anyway, recently I was searching my old Amazon orders for something else, and I came upon the Borage Oil. I can't believe I forgot to keep taking it! I've really been struggling to figure out why I've started getting zits again in the past few months when last year I had the problem completely under control. (If anything, I'm taking better care of my skin this year by using more natural products with less experimenting due to impulse skin care purchases.) Anyway, I realized that stopping the Borage Oil is the only real thing I've changed. I'm so glad that I figured this out!