Can someone help me out with HCG IU conversions?

Hello, I'm about to start my 3rd cycle in 2 weeks. This time I'm going to incorporate HCG. But I want to make sure my measurements are correct.

I have 9 vials of 1500 i.u HCG

I believe I'm supposed to add 1ml of solvent into each 1500 i.u of the HCG vials? Is this correct? I have those little insulin needles that hold up to 1ml. I want to do 250 iu every 3.5 days (500 iu/week total). So do I use 0.25 of a ml each time I inject? I'm not sure...

Thanks for your time.

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