Cialis (tadalafil) comes in two distinct dosing approaches: a lower dose taken every day, or a higher dose taken only when needed before sex. Which one you’re prescribed shapes how and when you take it, so understanding both matters.
As-Needed vs. Daily Dosing
The as-needed approach uses a higher dose, typically 10 mg, taken before sexual activity. Your prescriber may adjust this up to 20 mg or down to 5 mg based on how well it works and how you tolerate it. You take one tablet when you anticipate sex, and you don’t take more than one dose in a 24-hour period.
The daily approach uses a much smaller dose, either 2.5 mg or 5 mg, taken once every day at roughly the same time. The key advantage here is that you don’t need to plan around sexual activity at all. After several days of consistent use, the medication maintains a steady level in your body, so you’re ready whenever the moment arises. If you also have an enlarged prostate causing urinary symptoms, the daily 5 mg dose treats both conditions at once by relaxing smooth muscle tissue in the prostate and bladder, which improves urine flow.
When to Take It and How Long It Lasts
For as-needed use, most men take their dose at least 30 minutes before sex, though many find that allowing a full hour or two gives the medication time to reach its full effect. What sets Cialis apart from similar medications is its long window of action. Both the 10 mg and 20 mg doses have been shown to improve erectile function for up to 36 hours after a single dose. That doesn’t mean you’ll have an erection for 36 hours. It means that during that window, when you become sexually aroused, the medication is active and working to support blood flow.
For daily use, timing relative to sex is irrelevant. Just pick a consistent time of day, whether that’s morning, evening, or any other point that’s easy to remember. If you forget a dose, take it as soon as you remember. If it’s nearly time for your next dose, skip the missed one and get back on schedule. Never double up to compensate.
Food and Alcohol
One practical advantage of Cialis is that food doesn’t meaningfully delay its absorption the way it can with some other erectile dysfunction medications. You can take it with or without a meal, including after a heavy dinner, without worrying about reduced effectiveness.
Grapefruit juice is a different story. It interferes with the enzyme system your body uses to break down tadalafil in your gut. In animal studies, grapefruit juice increased peak blood levels of tadalafil by roughly 75% and extended the time it stayed in the body by about two and a half hours. Higher drug levels mean a greater chance of side effects, so it’s best to avoid grapefruit and grapefruit juice while using this medication.
Alcohol in small amounts is generally fine, but combining larger quantities with Cialis can drop your blood pressure noticeably. This can cause dizziness, lightheadedness, or fainting. A glass or two of wine is unlikely to cause problems, but heavy drinking on the same day you take a dose is a risk worth avoiding.
Common Side Effects
Most side effects are mild and tend to decrease as your body adjusts. In long-term safety data, the most frequently reported issues were headache (about 16% of users), indigestion (12%), nasal congestion or a runny nose (11%), and back pain (8%). Back pain and muscle aches are somewhat unique to Cialis compared to other medications in this class, and they typically appear 12 to 24 hours after a dose and resolve within a couple of days.
A few simple strategies can help. Taking an over-the-counter pain reliever can manage headaches and back pain. Eating something before or with your dose may reduce indigestion. If side effects persist or become bothersome at a higher dose, dropping to a lower one often solves the problem.
Who Should Not Take It
The most important safety rule with Cialis is absolute: do not combine it with nitrate medications used for chest pain (angina). This combination can cause a sudden, dangerous drop in blood pressure. This applies to all forms of nitrates, including tablets, sprays, and patches. If you use nitrates even occasionally, Cialis is not safe for you.
You should also let your prescriber know if you have low blood pressure, uncontrolled high blood pressure, serious liver problems, or have recently had a stroke or heart attack. People with certain heart conditions may need to be evaluated to ensure their cardiovascular system can handle the physical exertion of sexual activity itself.
Symptoms That Need Immediate Attention
Two rare but serious reactions require urgent care. The first is an erection lasting four hours or longer (priapism). This is a medical emergency because prolonged erection without blood flow cycling normally can cause permanent tissue damage. Don’t wait it out.
The second is sudden vision changes. A small number of men have experienced a condition affecting blood flow to the optic nerve, with visual symptoms typically developing within 6 to 36 hours after taking the medication. Any sudden decrease or loss of vision in one or both eyes warrants stopping the medication and seeing an eye doctor immediately.
Storage
Keep tablets at room temperature, ideally around 77°F (25°C), with a safe range of 59 to 86°F. Store them away from moisture, so a bathroom medicine cabinet exposed to shower steam isn’t ideal. A bedroom drawer or closet shelf works better.