Cialis (tadalafil) comes in four tablet strengths: 2.5 mg, 5 mg, 10 mg, and 20 mg. The right dose depends on whether you’re taking it as needed before sex or once daily, and whether you’re treating erectile dysfunction, an enlarged prostate, or both. The standard starting dose for as-needed use is 10 mg, while daily use starts at 2.5 mg.
As-Needed Dosing for Erectile Dysfunction
The typical starting dose is 10 mg taken as a single tablet, no more than once a day, at least 30 minutes before you expect sexual activity. From there, your prescriber may adjust you up to 20 mg or down to 5 mg based on how well it works and whether you experience side effects.
What sets Cialis apart from other erectile dysfunction medications is its long window of effectiveness. A single dose can improve erectile function for up to 36 hours after taking it, which is why it’s sometimes called “the weekend pill.” The drug reaches its peak concentration in your blood at a median of about 2 hours, though this can range anywhere from 30 minutes to 6 hours depending on the person. That wide range means some men notice effects quickly while others need more patience.
You can take it with or without food. Unlike some other ED medications, a heavy meal won’t significantly delay absorption. One thing to watch: large amounts of grapefruit juice can raise the drug’s levels in your blood, potentially increasing side effects.
Daily Low-Dose Use
If you prefer not to plan around a pill, a daily regimen is the other option. The starting dose is 2.5 mg once a day, taken at the same time each day, regardless of when sexual activity might happen. Your prescriber may increase this to 5 mg daily if the lower dose isn’t effective enough.
Daily dosing builds a steady level of the drug in your system, so you don’t need to time anything around sex. This approach tends to work well for men who are sexually active more than twice a week, since the as-needed approach would mean frequent dosing anyway. It can take several days of consistent use before you notice the full benefit.
Dosing for an Enlarged Prostate
Cialis is also prescribed at 5 mg once daily to treat symptoms of benign prostatic hyperplasia (BPH), the medical term for a non-cancerous enlarged prostate that makes urination difficult. If you’re being treated for both BPH and erectile dysfunction at the same time, the dose is the same: 5 mg once daily. There’s no need to take separate doses for each condition.
Age and Kidney or Liver Concerns
Adults over 65 do not need a different dose based on age alone. However, kidney or liver problems can affect how your body processes the drug. If you have significant impairment in either area, your prescriber will typically start you at a lower dose or recommend longer gaps between as-needed doses, since the drug stays in your system longer when your body can’t clear it at the normal rate.
The One Interaction That Matters Most
Cialis should never be combined with nitrate medications, which are commonly prescribed for chest pain (angina). Nitrates include nitroglycerin tablets, patches, and sprays, as well as isosorbide. Both drugs lower blood pressure through similar pathways, and combining them can cause a dangerous, potentially life-threatening drop in blood pressure that leads to cardiovascular collapse.
This isn’t just a timing issue you can work around. Because Cialis stays active in your body for up to 36 hours, you should not use any nitrate medication even days after your last dose without guidance from a prescriber. The interaction risk with nitrates applies to all doses of Cialis, whether you’re on 2.5 mg daily or 20 mg as needed.
What to Expect in Practice
Most men start on the 10 mg as-needed dose, try it a few times, and then adjust from there. If it works well but causes headaches, flushing, or nasal congestion, stepping down to 5 mg may reduce those side effects while still being effective. If 10 mg isn’t strong enough, 20 mg is the maximum single dose. Never take more than one dose in a 24-hour period regardless of the strength.
The 36-hour window doesn’t mean you’ll have an erection for 36 hours. It means that during that window, you’re more likely to achieve and maintain an erection when you’re sexually aroused. The drug works by increasing blood flow in response to arousal, not by triggering an erection on its own. If you experience an erection lasting more than 4 hours (a condition called priapism), that’s a medical emergency requiring immediate treatment.