I took two Nyquil at 2300 and woke up at 0530 to get ready for work.. After 5 minutes in shower, I got extremely light headed and dizzy, needed to sit down, and the feeling did not resolve for maybe 5 minutes (even sitting down). I went back to bed, woke up at 1030 and after approx. 5 minutes standing, same thing happened.. I still feel a bit lightheaded and dizzy now but it is definitely less severe than this morning. These are listed as some severe side effects of this medication but I am unsure if I should rush to a doctor. I have taken one Nyquil before and I was fine so I m assuming two is too much.. I am 29 with no previous heart issues. I m planning to wait a bit, see how my symptoms are, then proceed to a doctor in the afternoon if things do not approve??