Hi Sharmam and welcome to the forum.
As Tubs said there is a lot of valuable information on the other Byetta thread, but to answer your specific question - unfortunately we all react to Byetta differently. It is a synthetic hormone and, because it's not natural to the human body, the body's natural reaction is to reject it, which it does by making you vomit it out of your system. Some people seem to be more tolerant to it than others, and males seem to experience far less nausea than females, although no-one knows why.
There are several on the forum who experienced several weeks of nausea before their bodies finally became acclimatised to Byetta, and they now find they can eat pretty much whatever they want without feeling the slightest bit queasy. But, and it is a VERY BIG BUT, the manufacturer's guidelines to doctors say that it is essential that a patient is not moved on to the higher dose until they are fully acclimatised to the lower dose (i.e. until there has been at least 2 weeks with no nausea on the 5mcg dose). If you doctor moves you up to the 10mcg level while you are still feeling sick on 5mcg, then it is a 100% guarantee that you will become violently and uncontrollably sick. Some patients have needed to be hospitalised because of their doctor's negligence in not following the manufacturer's instructions.
There is no reason why you should not continue on the 5mcg dose for a further month, or as long as it takes for your body to stop trying to reject the Byetta - it doesn't cost the NHS any more to do this, and for some patients the 5mcg dose is as much as they need in order to get good blood sugar control.
