The injection at my urologist to show me how to inject and test the dosage was at .05 cc. I had virtually no response with that. Since everyone is different, you have to experiment. I've tried .2 to .5cc. My initial experimentation was skewed by degradation of the medication until I learned of freezing it in the syringes to prolong shelf life. I think I have it narrowed down between .2 and .3. However, yesterday I used a .3 dose and had a hard erection for a solid three hours. Tough to ask anyone else to "enjoy" that with you for that long. (-:
I should add that I've been using (at urologists suggestion) a vacuum pump during my down time to help keep the blood supply lines open and my T-levels have returned to normal post ADT.