Tadalafil 20 mg: What the Label Says About the Highest ED Dose

The Cialis label starts most men at 10 mg and allows 20 mg after adjustment. Side effects rise with dose, and some conditions cap the dose lower.

Tadalafil 20 mg is the highest as-needed dose on the Cialis label for erectile dysfunction (ED), but it is not the recommended starting dose. The label starts most men at 10 mg before sexual activity and allows an increase to 20 mg or a decrease to 5 mg depending on response and tolerability, no more than once a day in most patients.¹ Tadalafil 20 mg also carries more side effects than 10 mg in the label's trial tables, and several health conditions and medicines cap the dose lower.¹

What is tadalafil 20 mg used for?

The 20 mg tablet is one of three strengths of Cialis (5, 10 and 20 mg).¹ For ED taken as needed, the label describes 20 mg as an upward adjustment: "the dose may be increased to 20 mg or decreased to 5 mg, based on individual efficacy and tolerability."¹ It is not a daily-use strength. The once-a-day ED and prostate regimens use 2.5 mg or 5 mg, and our article on tadalafil 5 mg covers that schedule.¹

The same active ingredient is also sold as Adcirca, a separate product with its own label, which the Cialis label names when it warns against taking the two together.¹ The choice of strength belongs to the prescriber who knows the patient's other conditions and medicines.

Is tadalafil 20 mg stronger than 10 mg?

In the trials behind the label, 20 mg did better than placebo. In the two primary US trials (402 men, mean age 59), the erectile function domain score rose by 6.9 and 9.3 points on 20 mg against changes of -0.2 and 0.3 on placebo, and the share of attempts with erections lasting long enough for intercourse rose by 34 and 44 points against 5 and 4.¹ Five trials outside the US tested 5, 10 and 20 mg and showed significant gains in all three measures. The label's tables do not set 10 mg and 20 mg side by side in one comparison, so a head-to-head difference has to come from pooled analyses.¹

A 2026 network meta-analysis pooled 83 double-blind, placebo-controlled trials with 6,029 participants and reported odds ratios against placebo for reaching satisfactory erectile function (IIEF domain score above 26): 7.13 for tadalafil 20 mg and 3.14 for tadalafil 10 mg.² The same analysis found the odds of treatment-related adverse events were lowest for tadalafil among the four PDE5 inhibitors, though with wide confidence intervals. Several authors work for Viatris, a sildenafil manufacturer, which the paper discloses, and indirect comparisons carry uncertainty.²

Who may benefit from the higher dose?

A prespecified subgroup analysis and a pooled analysis of three placebo-controlled trials, by authors employed by Lilly, looked at men with severe ED (IIEF erectile function domain score of 1 to 10). In the pooled data, men on 20 mg had a larger gain than men on 10 mg in the domain score (13.6 vs 10.4) and in the share of attempts with erections lasting long enough for intercourse (56% vs 43%). The authors suggested men with severe ED, particularly with an organic comorbidity, may gain more from 20 mg. In the single Japanese study, the differences were not statistically significant, and both doses were well tolerated.³ The study is a subgroup and post hoc analysis, so it describes a pattern rather than a rule for any one man.

How fast does tadalafil 20 mg act, and how long does it last?

The label says the peak blood level comes between 30 minutes and 6 hours after a dose, with a median of 2 hours, and that food does not change the rate or extent of absorption.¹ A home-based, stopwatch study in men with ED found a statistically significant response to 20 mg from 16 minutes after dosing, while the 10 mg response approached significance at 30 minutes; 52% of men on 20 mg had at least one successful intercourse within 30 minutes versus 35.1% on placebo.⁴ The label states that as-needed tadalafil improved erectile function compared with placebo up to 36 hours after the dose, and the terminal half-life is about 17.5 hours in healthy subjects.¹

That long window is why the maximum is once per day. Taking a second 20 mg tablet because the first seems slow adds drug to a body that clears it slowly. For the timing of the other pills, see sildenafil with or without food.

What are the side effects of tadalafil 20 mg?

The label's table lists reactions reported by 2% or more of men and more often than on placebo, across eight placebo-controlled studies of as-needed use. Rates rise with dose:¹

In those studies, 3.1% of men on 10 or 20 mg stopped because of adverse events, versus 1.4% on placebo.¹ An erection lasting more than 4 hours needs emergency care, and sudden vision loss in one or both eyes means stopping the drug and seeking medical care.¹

When is the 20 mg dose not suitable?

The label sets lower limits in several situations, which is why a prescriber reviews the medicine list before raising the dose:¹

• Nitrates. Tadalafil is contraindicated with any form of organic nitrate, because it increases the blood-pressure-lowering effect. The same applies to the guanylate cyclase stimulator riociguat.¹
• Strong CYP3A4 inhibitors such as ketoconazole or ritonavir. The as-needed maximum is 10 mg, no more often than every 72 hours.¹
• Mild or moderate liver impairment. The dose should not exceed 10 mg per day, and use in severe impairment is not recommended.¹
• Kidney impairment. With creatinine clearance of 30 to 50 mL/min, start at 5 mg with a maximum of 10 mg not more than every 48 hours; below 30 mL/min or on dialysis, the maximum is 5 mg not more than every 72 hours.¹
• Alcohol. Substantial intake (about five units or more) with tadalafil can increase orthostatic symptoms such as dizziness and a fast heart rate.¹

Alpha-blockers and other blood pressure medicines also need review, covered in ED pills and blood pressure medicines and ED medication interactions. Adding a second PDE5 inhibitor is a separate question, answered in sildenafil and tadalafil together.

Is tadalafil 20 mg also used for pulmonary hypertension?

Yes, but under a different brand and dose. Adcirca, the tadalafil product for pulmonary arterial hypertension, is dosed at 40 mg once daily, taken as two 20 mg tablets, and the label says not to divide the 40 mg over the day.⁵ That is a daily treatment regimen for a different condition, not the as-needed ED dose. The Cialis label tells patients not to take Cialis and Adcirca together.¹ If a pharmacy label says "tadalafil 20 mg", the prescriber's directions and the condition being treated decide how it is taken.

Is tadalafil 20 mg used for an enlarged prostate (BPH)?

Not at this strength. The Cialis label's recommended dose for once-daily use in benign prostatic hyperplasia, alone or started with finasteride, is 5 mg taken at about the same time every day.¹ The 20 mg tablet is the upper as-needed ED dose, so it is not a BPH dose. Men with both ED and BPH are covered in the label's once-daily 5 mg regimen, and our tadalafil 5 mg article explains it.

What to ask before moving from 10 mg to 20 mg

A dose change is a clinical decision. Useful questions: how did the 10 mg dose go, and over how many attempts; which heart, liver, kidney or prostate conditions apply; which medicines, including nitrates and alpha-blockers, are on the list; and what is the plan if side effects such as headache or indigestion show up. The AUA guideline treats PDE5 inhibitors as a standard option where appropriate and frames treatment as shared decision-making.⁶

Questions readers ask

Is tadalafil 20 mg the normal dose?

No. The label's recommended starting dose for as-needed use is 10 mg. The dose may be increased to 20 mg or decreased to 5 mg based on response and tolerability.

How long does tadalafil 20 mg last?

The label says as-needed tadalafil improved erectile function compared with placebo for up to 36 hours after dosing. The terminal half-life is about 17.5 hours.

Can I take tadalafil 20 mg every day?

No. The maximum recommended frequency for as-needed use is once per day in most patients, and daily-use regimens use 2.5 mg or 5 mg.

Does food affect tadalafil 20 mg?

The label says the rate and extent of absorption are not influenced by food, so it can be taken with or without food.

Who should not take tadalafil 20 mg?

Anyone using a nitrate cannot take tadalafil at any dose. Men with certain liver or kidney problems, or taking strong CYP3A4 inhibitors, have lower maximums.

Is tadalafil 20 mg used for BPH or pulmonary hypertension?

Not as an as-needed ED dose. The Cialis label gives 5 mg once daily for BPH, and the pulmonary hypertension product Adcirca is 40 mg once daily as two 20 mg tablets.

Further reading

Part of our guide: How ED Medications Work: Timing, Food, Interactions and Combinations

• Sildenafil Headache: How Common Is It?
• Tadalafil With Alcohol: How Much Is Too Much?
• What Is Tadalafil Used For? The Three Approved Uses
• Tadalafil Brand Names: Which Brand Is Used for What