Like "I started reusing needles when I was 16 on my doctor's advice. Did so for the next 25 years with no ill effect. I only used each syringe for 24-hours though and then got rid of it. Also, if you take more than three injectins, that needle will get pretty painful. The only thing I would worry about though is using the same syringe for the two different insulins. Levimir is not supposed to be mixed with other insulins, so there could be some problems having it in the same syringe even at different times. Novolog will make any traces of Levimir cf levemir crysalize. Actually Lantus will crystalize. Not sure what Levimir would do."