Cialis (tadalafil) can be recommended for use by your health care provider if you are unable to have sex due to the fact you can't get an erection that would be firm enough. Diarrhea, indigestion, heartburn, headache, facial flushing and stomach pain are the most commonly experienced mild side effects. These go away on their own in most cases. In case they do not go away soon, make sure you report them to your doctor. In some cases these side effects can become quite bothersome or change in intensity- in that case you may be required a dose adjustment that will eliminate the unpleasant symptoms. If you think you have taken too much of Cialis and experience overdose symptoms, such as flushing, headache, indigestion, stuffy or runny nose, heartburn, pain in the back or muscles and some other symptoms that can be individual for every person, seek emergency help.