Hello all, New here, and had a question about Lantus. I know that Lantus is suppose to lose it's potency at 28 days, but I had a question about that. I just opened a vial of Lantus and used it once, (I found my other vial on the counter, was having one of those days, afterwards). So I guess my question is, this one vial I used once, would it still be good for longer than 28 days, or would I have to toss it? I still have more than half of the other vial, and really don't feel like throwing away a brand new bottle...HELP?!