Cialis (tadalafil) is taken either once daily at a low dose or as needed before sexual activity, depending on which regimen you’re prescribed. The as-needed dose is 10 mg or 20 mg, taken no more than once in a 24-hour period. The daily dose is 2.5 mg or 5 mg, taken at the same time every day regardless of when you plan to have sex.
As-Needed Dosing: 10 mg or 20 mg
Most people start with 10 mg taken before anticipated sexual activity. If that works well, you stay there. If it’s not enough, the dose can be increased to 20 mg. If side effects are bothersome, it can be dropped to 5 mg. In all cases, the hard rule is no more than one dose per day.
Cialis reaches its peak concentration in your blood anywhere from 30 minutes to 6 hours after you take it, with a median of about 2 hours. That’s a wider window than most people expect. The drug then stays active for up to 36 hours, which is why it’s sometimes called “the weekend pill.” That long window means you don’t need to time your dose as precisely as with shorter-acting alternatives. Taking it an hour or two before sexual activity is a reasonable starting point, but many men find it still works well the following day.
If you’re taking certain medications that affect how your liver processes drugs (strong CYP3A4 inhibitors like ketoconazole or ritonavir), the maximum as-needed dose drops to 10 mg, and you should wait at least 72 hours between doses instead of the usual 24.
Daily Dosing: 5 mg Once a Day
The daily regimen uses a smaller dose, typically 5 mg, taken at roughly the same time each day. This approach keeps a steady level of the drug in your system so you don’t need to plan around a pill. It’s a good fit if you have sex more than twice a week or prefer spontaneity without timing a dose beforehand.
Daily dosing is also the standard approach when Cialis is prescribed for an enlarged prostate (benign prostatic hyperplasia), either on its own or alongside other prostate medications. The dose is the same 5 mg once daily.
If you miss a dose on the daily schedule, take it as soon as you remember. If your next dose is coming up soon, skip the missed one and get back on schedule. Never double up to compensate.
How the Two Schedules Compare
Both regimens are effective. A systematic review comparing daily dosing (5 to 10 mg) against as-needed dosing (10 to 20 mg) found that both improve erectile function. The choice comes down to lifestyle preference and how often you’re sexually active. Daily dosing eliminates the need to think about timing but means taking a pill every day whether you need it or not. As-needed dosing uses a higher single dose but only when you want it.
There’s no medical reason to prefer one over the other for most people. Some men try as-needed dosing first and switch to daily if they find themselves reaching for the pill more than a couple of times a week.
Long-Term Daily Use
If you’re wondering whether it’s safe to take Cialis every day for months or years, the clinical data is reassuring. In open-label extension studies, men took 5 mg daily for up to two years. No serious drug-related adverse events were observed. The most common side effects over the first year were indigestion, headache, and back pain, all consistent with what’s seen in shorter trials. Lab work and heart rhythm monitoring showed no clinically meaningful changes over that period.
Effectiveness also held up. After two years of daily use, more than 95% of participants reported improved erections, and those improvements didn’t fade over time. The benefits at the two-year mark were essentially the same as at one year.
Food, Alcohol, and Grapefruit
You can take Cialis with or without food. Unlike some medications, a high-fat meal doesn’t meaningfully delay its absorption. Alcohol is a different story. A single drink is unlikely to interfere, but heavy drinking works against you by making erections harder to achieve in the first place. If you’re taking Cialis for erectile dysfunction, keeping alcohol moderate gives the drug the best chance to work.
Grapefruit juice is one to avoid entirely. It interferes with the enzyme system that breaks down tadalafil, which can raise drug levels in your blood unpredictably.
A Critical Safety Limit With Nitrates
Cialis causes blood vessels to relax. Nitrate medications, often prescribed for chest pain, do the same thing through a different pathway. Combined, the blood pressure drop can be dangerous. Research published in the Journal of the American College of Cardiology found that the interaction between tadalafil and nitroglycerin lasts a full 24 hours and doesn’t fully clear until 48 hours after the last dose. That’s why guidelines recommend waiting at least 48 hours after taking Cialis before using any nitrate medication. This applies to both the daily and as-needed regimens.