there are a number of schemes for taking both together, there is supposedly a synergy between the two as far as creating new cells go, but there is also some hypothesis that both cannot be active in the body at the same time, so there have been questions as to timing. I have heard of some knowledgeable vets doing a couple weeks of pmgf followed by the igf and getting good results. In fact I have read where one researcher got better results that way than doing them at the same time. As for me, I only do pmgf, I am very sensitive to hypo feelings, and though supposedly you cant get dangerously hypo from igf, I dont like the feeling of it, so I stick with hte pmgf, but that is just my experience. There are actually many more who would choose igf over pmgf. Pmgf has gotten a bad rep due to too small dosages being used, when it came out the schedule called for 500mcg/week, I would not go under 1mg, and 1.5-2 seems best. I also think some people associate the hypo feeling, and the hand tingling some get from igf with extra effectiveness and neither of these are present with pmgf, I had 0 negative sides, it was probably one of the better recomp research I have done and the best use of my time in between hormonals.