Use protective measures and ask your doctor if you have any questions about this. For example, a Cialis pill with 2. How often can you take Cialis? Do not take more than directed 1 tablet a day. Drinking excessive alcohol can temporarily reduce your ability to get an erection.How Quickly It Works Cialis is a prescription drug that contains the active ingredient tadalafil. The Food and Drug Administration (FDA) approved its use in people .  · One dose of Cialis can help improve erectile function for up to 36 hours. In comparison, Viagra’s effects can last up to 4 hours. But on average, its effects start to . The effect of one tablet lasts for up to 36 hours. The recommended ‘as needed’ dose for Cialis is 10mg, taken prior to anticipated sexual activity. The dose may .