Tadalafil 10 mg vs 20 mg: What's the Difference?

A question patients often ask me is: "Doctor, 20 mg is stronger, so it must be better, right?" The short answer is: not always. The right dose is the lowest dose that works well enough, with side effects you can accept. Let's look at the details.

A quick recap: what is tadalafil?

Tadalafil is a PDE5 inhibitor. It helps the blood vessels in the penis relax so that blood flows in more easily when you are sexually stimulated. It is used to treat erectile dysfunction (ED) and urinary symptoms from an enlarged prostate. For the full basics, read Tadalafil (Cialis): how it works.

Comparing 10 mg and 20 mg

A common misunderstanding is that 20 mg lasts longer. In reality the duration is about the same. The difference is the blood level, which means a stronger effect in some men, and more side effects too.

In the main studies, both doses were clearly better than placebo, and 20 mg gave slightly higher average erection scores than 10 mg, but not everyone needs the higher dose.

How doctors choose the dose

1. Start at 10 mg for most men, then assess after 4–6 real attempts.
2. Increase to 20 mg if the effect still isn't enough and there are no worrying side effects.
3. Reduce to 5 mg if side effects are bothersome, or if something raises the blood level of the drug.
4. Consider a low daily dose if you have sex often or have an enlarged prostate. See Daily vs on-demand tadalafil.

Before concluding that the medicine "doesn't work", check whether it has been used correctly. Was there enough sexual stimulation? Have you tried several times? Were you drinking heavily? Were you very anxious? Many men get better results once these are sorted, without needing a higher dose.

Who needs a lower-than-usual dose

• Reduced kidney function: with moderate impairment, men usually start at 5 mg with limited frequency; with severe impairment, no more than 5 mg with longer gaps between doses
• Reduced liver function
• Taking strong CYP3A4 inhibitors, such as ketoconazole, itraconazole, clarithromycin or HIV medicines containing ritonavir/cobicistat: the on-demand dose should not exceed 10 mg every 72 hours. If you take HIV medicines, see also HIV treatment and the TLD regimen
• Taking alpha-blockers for the prostate or blood pressure: start cautiously

Dose adjustment figures from the prescribing information

CrCl (creatinine clearance) is a measure of kidney function that your doctor calculates from a blood test.

Precautions for every dose

• No more than once a day, and not together with another PDE5 inhibitor
• Don't combine it with large amounts of alcohol
• Men with heart disease should be assessed to make sure their body is ready for sexual activity
• Go to hospital immediately for an erection lasting more than 4 hours, chest pain, sudden blurred vision or sudden hearing loss (in Thailand call 1669)

Back pain and muscle aches

These are side effects fairly specific to tadalafil. They usually start 12–24 hours after a dose and go away on their own within 48 hours, and most are mild. If they bother you, your doctor may lower the dose or change the medicine. If the pain is severe or hasn't gone after 2 days, see a doctor.

The 5 mg daily option

For men who have sex often, don't want to plan around timing, or also have urinary symptoms from an enlarged prostate, a doctor may consider low-dose daily tadalafil (2.5–5 mg). Blood levels become steady after about 5 days of daily use. It is not suitable for men with severely reduced kidney function. Read the comparison in Daily vs on-demand tadalafil.

Choosing 10 or 20 mg in real situations

These are general examples; your actual dose must be assessed by your doctor.

• A healthy man in his 30s whose main issue is anxiety usually starts at 10 mg, and for many that is enough.
• A man in his 50s with diabetes and moderate ED may need to move up to 20 mg.
• A man who gets back pain every time on 20 mg may step down to 10 mg or change medicine.
• A man on ritonavir-containing HIV medicines or with reduced kidney function needs a lower dose, as in the table above.

The doctor's summary

Dosing is not a contest about who takes the strongest. 10 mg is enough for many men, and 20 mg is an option when needed. What helps the medicine work much better is treating the underlying cause at the same time, such as controlling blood sugar, blood pressure, weight and stress. Read about the causes in What causes erection problems.

Getting advice on your dose at Dr. Kris Clinic

We review your health history, chronic conditions, current medicines and your goals before recommending the right dose and form of treatment, then follow up and adjust the plan. You can see us at the clinic in Surat Thani or online, and consultations in English are available.