Botox should be used within 24 hours of reconstituting(mixing) it. With that said, two weeks later, if kept at a cool temperature, it will likely be okay. However, why would you want to spend your good money on Botox that has been sitting around for 2 week. For our patients, we always open a new vial and reconstitute in front of them and use the Botox right away. This way, our patients know that they are getting the freshest Botox available. Our profit margin may be lower this way, but it ensures our patients are getting the best care. If your injector has Botox sitting around for 2 weeks and has not injected it, then they must not do very many Botox injections in their practice and you may want to go to someone more experienced. In our office, we go through multiple vials each day, so Botox sitting around for 2 weeks is never an issue.
Good Luck.