I started taking this last week (7 days ago) and I seem to be waking up early morning with severe nausea and have vomited a few times. If I manage to sleep thru the morning then Im ok. Its not happened every day but frequently. I can't be sure its a "side effect" or not but the reason I mention it is because the first poster said he had nausea and I am in fact experiencing it, but I am taking other medications with the Mucinex DM