IVF meds missing

My IVF stimulation medications consist of 5 units of Lupron, 225 units of Gonal-F and 2 viles of Menopur. So...I draw up the Lupron and inject into a Menopur. I draw up the 225 of Gonal and inject into Menopur that has the Lupron already in it. When I draw out that fluid I get 225 units back in my syringe. Then I take that fluid and put it into my second Menopur vile however when I draw it back up again, I get less than 225 units back!!! So frustrating, what am I doing wrong?! Anyone else have issues?