peter- if it's mixed with bacteriostatic water, which it probably is, the preservative in that is only good for 30 days. that doesn't mean it might not last a little longer, because expirations dates will err on the side of caution. but Dr. Geddes, who does this full-time and i believe also has her phD in bio-chem, says that the hcg starts to lose potency from day one. that might explain you getting better results if you increased your dose as time goes on. my doc never allows anyone to buy more than 14 day's worth of shots at a time, and she's been doing the protocol with patients for 10 years. i don't have any clinical research to back up my opinion, but from an anecdotal point of view it appears that most people start to notice a difference in their hcg after about 12-14 days, and they then do better again after mixing fresh hcg.

also, if you're ordering your own, it's cheap enough that i don't think it's worth the risk to use it for longer than 2 weeks. guys are generally going to lose a lot of weight pretty much no matter what they do, but for the fairer sex it's a bit more of a challenge...