You can, but I don't recommend it and this is why. Dose of hCG is very individual and is important to both experiencing the least hunger and best weight loss - if you pre-load your needles you will not be able to effectively adjust your dose of hCG as necessary - both at the start when you may not be sure what your best dose is just yet, and then once you find it, it's common to need to reduce your dose as you get thinner - so I prefer to leave the hCG in the bottle and draw up the hCG each on the protocol so I can have control over how much I'm injecting and have that ability to adjust as needed.
This medication is taken once there is a mature egg follicle in the ovary. Your doctor will most likely give you a specific time or time frame to take the medication. It is important to tell your doctor if you do not take the medication on time in case any adjustments need to be made. If you will be having intercourse or intrauterine insemination, ovulation will occur approximately 36 hours later, so the day of the injection and two days following it are your critical days. If you will be having egg retrieval as in an IVF cycle, it will occur close to that 36-hour mark so as to optimize the maturation but avoid ovulation.