I don't have an answer for you, but a lot depends on how and where you store the mixed solution. The substance is supposedly fragile. So avoid shaking and other harsh treatment. It will also last longer in the refrigerator. I mix mine then fill all the syringes and put the syringes in the freezer. I then take out a syringe and allow it to thaw which takes less than 10 minutes. I don't use hcg for fertility but my balls are large and full.How long will Pregnyl 10,000 USP last after mixed when using the 10ml solution it comes with? Also, what is the recommended dose for sperm count to increase when used with TRT?