+1 for Dena's comments.
The Estradiol does not deteriorate in a few months. It takes years, well after the vials expiration date, for any significant deterioration to happen. Heat and ultra violet light will hasten this deterioration.
The main problem after a vial is punctured is bacterial and viral contamination. Make sure you wash your hands before drawing up your injection and use good sterile technique. Try not to puncture a core of rubber from the vial's top. This may let in bacteria and viruses from the environment. In hospitals, we have drug handling policies that limit how long a multi dose vial may be kept for reuse after it is first punctured. Usually the maximum limit is 30 days. This is an arbitrary number mainly because hospitals are full of drug resistant bacteria. In a home environment, it may be safe to extend this a bit longer, but there are no published guidelines. If the liquid has become cloudy or discolored, this may be a sign of contamination, but not always.
The most important thing to do is wash your hands, wipe the vial top with alcohol and use good drawing and injecting technique.
