I took 25mg of viagra 12 hours ago I am feeling lightheaded still ,it doesn't usually happen as I have taken it for years with no problems... I was feeling tired when I took it 12 hours ago and after sex I went to sleep but woke up feeling a little dizzy.I thought the effects of Viagra lasts only for 4 hours not 12 hours.I probably should not take the pill and have sex when I am not feeling up to par. Any suggestions

More info would be appreciated but we can't give you a determination for obvious reasons, we are not doctors or urologists.

I would say though that depending on your cardiovascular system and your age, if you feel lethargic after sex, consult with your doctor for a complete physical check up.

The only valid suggestion is to see your doctor.