Cialis typically starts working in about 30 minutes after taking it, but it may take up to 1 to 2 hours to feel the full effects. The medication reaches its peak concentration around 2 hours post-dose. Cialis effects can last up to 36 hours, allowing a long window for sexual activity. It is important to note that sexual arousal is still necessary for Cialis to work, as it helps improve blood flow but does not cause an erection on its own.