The recommendation is to take Nexium on an empty stomach about half an hour before a meal in the morning. I believe this is because this is the way it was tested to be best absorbed and best used by the body. For me this was not a good way to take it because it did not fit into my routine and I would often forget it. So, in the long run a pill taking at the "wrong" time was better than a pill not taken at the "right" time. I always took mine before I went to bed. I now do the same with my Pepcid which I take twice a day. I do often forget my am dose of the Pepcid so I keep a bottle of it in my car "just in case."
It's important to discuss changing the way you take your meds if they differ from what your doctor recommends though. There is always the possibility your doctor is suggesting you take it a certain way that we are unaware of. Chances are it won't be an issue but it's always better safe than sorry.