heres the drug liturature that is supplied with Pregnyl HCG.It states its stable for 60 days when refrigerated.
http://www.rxlist.com/pregnyl-drug.htm
Directions for Reconstitution
Two-vial package: Withdraw sterile air from lyophilized vial and inject into diluent vial. Remove 1–10 mL from diluent and add to lyophilized vial; agitate gently until powder is completely dissolved in solution.
Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
IMPORTANT: USE COMPLETELY AFTER RECONSTITUTION. RECONSTITUTED SOLUTION IS STABLE FOR 60 DAYS WHEN REFRIGERATED.