Which Cialis (tadalafil) dose is best for erectile dysfunction?
Most men start with either 10 mg “on demand” or 5 mg once daily — the right choice depends on how often you have sex, your other health conditions, and side-effect tolerance.
Cialis — the brand name for tadalafil — comes in 2 main dosing styles: a low 2.5- or 5-mg tablet you swallow once daily, and higher 10- or 20-mg tablets you take “on demand” at least 30 minutes before sex. Daily dosing keeps a steady level of medicine in your bloodstream, while on-demand dosing gives a stronger single-dose boost that lasts up to 36 hours. Most first-time users try 10 mg on demand, but men who have sex at least twice a week or prefer spontaneity often feel better on the 5 mg daily plan. Your doctor can safely raise or lower the dose based on results and side effects.
- Cialis starts working in as little as 30 minutes and can last up to 36 hours per dose.
- Using Rx.com to compare prices lowers the cost of generic tadalafil to about $11 for a 20-mg tablet or $9 for four 5-mg pills.
Cialis is an FDA-approved PDE5 inhibitor for ED
Cialis is the longest-acting member of the PDE5-inhibitor class, which also includes sildenafil (Viagra) and vardenafil. By blocking the phosphodiesterase-5 enzyme, tadalafil keeps nitric-oxide-stimulated blood flow high in the penis, making it easier to get and keep an erection when you’re sexually aroused.
Fast definition: Erectile dysfunction is the consistent inability to achieve or maintain an erection firm enough for satisfactory sex; PDE5 inhibitors like Cialis boost penile blood flow but still require sexual stimulation to work. See our in-depth ED causes & treatment guide to learn more.
Tadalafil’s half-life determines the best schedule
With a half-life of about 17 hours, tadalafil stays active far longer than sildenafil (4 hours). A single 10- or 20-mg tablet often supports erections for up to a day and a half, giving it the nickname “the weekend pill.” Daily 5 mg dosing, meanwhile, maintains a steady-state level within 5 days, smoothing out peaks and troughs.
Why this matters: Men who want spur-of-the-moment sex benefit from daily dosing, while those with infrequent sex can save pills — and money — with the on-demand plan.
Higher doses work faster, but daily 5 mg improves consistency
Clinical trials show all approved doses outperform placebo, but response rates climb with dose — up to a point.
| Tadalafil dose | Avg. IIEF-EF improvement* | % men achieving firm erection | Onset of action |
|---|---|---|---|
| 5 mg daily | +6.5 points | 71 % | N/A (steady state) |
| 10 mg on demand | +7.9 points | 76 % | 30–45 min |
| 20 mg on demand | +8.4 points | 80 % | 25–30 min |
*Pooled data from randomized trials lasting ≥ 12 weeks.[pubmed.ncbi.nlm.nih.gov]
Daily vs. on-demand: how to decide which plan fits your life
The right dose depends on frequency of sexual activity, cardiovascular health, medication interactions, and personal preference.
Frequency of sex: If you typically have sex ≥ 8 times per month, daily 5 mg costs about the same as taking 8–10 on-demand pills and feels more spontaneous.
Other medicines: Alpha-blockers for prostate or blood-pressure drugs can drop your blood pressure further when combined with higher tadalafil doses; many doctors start these patients at 5 mg daily.
Liver or kidney disease: Severe renal impairment usually requires dose reduction to 5 mg every other day or avoidance of the 20 mg strength.
Side-effect sensitivity: Headache and flushing scale with dose; if 20 mg works but produces a headache, dropping to 10 mg or daily 5 mg often fixes the problem.
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Side-effect risk rises as the dose goes up
All PDE5 inhibitors share similar adverse-event profiles, but tadalafil’s longer action means headaches or back pain can linger a bit longer.
| Side effect | 5 mg daily | 10 mg on demand | 20 mg on demand |
|---|---|---|---|
| Headache | 4 % | 6 % | 11 % |
| Flushing | 3 % | 5 % | 8 % |
| Nasal congestion | 2 % | 3 % | 6 % |
| Back pain | 1 % | 3 % | 5 % |
| Dyspepsia | 2 % | 4 % | 6 % |
Percentages represent any-grade events reported in pooled manufacturer-sponsored trials (n ≈ 1,800).[pubmed.ncbi.nlm.nih.gov]
How much does Cialis cost — and how to save
Brand-name Cialis averages about $63 per 20-mg tablet at major U.S. pharmacies. Generic tadalafil has driven the price down dramatically.
| Product | Typical cash price* | Rx.com discount price† | Per-dose savings |
|---|---|---|---|
| Cialis 20 mg (brand) | $63 | $48 | $15 |
| Tadalafil 20 mg (generic) | $18 | $11 | $7 |
| Tadalafil 5 mg (30-day) | $85 | $55 | $30 |
*National average cash price, May 2026. †Lowest price found through the Rx.com comparison tool on the same date.
Use Rx.com to compare prices — most patients pay under $60 for a month of daily 5 mg tablets with a free discount card.
Not sure whether to ask your doctor for daily or on-demand Cialis?
Check the column that fits your situation:
✅ Daily 5 mg makes sense if…
- You plan sex at least twice a week
- You want maximum spontaneity
- You experienced headaches on higher doses
- You take alpha-blockers for BPH
🏥 On-demand 10–20 mg is better if…
- You have sex fewer than 8 times a month
- You’re sensitive to daily costs
- You prefer clear “on/off” medication days
- Your kidney function is below eGFR 30 mL/min
🚨 When to Contact Your Healthcare Provider
Contact your doctor immediately if you experience any of the following:
- Sudden vision loss — may signal NAION, a rare optic-nerve problem
- Hearing decrease or ringing — could be PDE5-related ototoxicity
- Priapism lasting > 4 hours — prolonged erection can cause permanent damage
- Chest pain or shortness of breath — especially after sexual activity
- Severe dizziness or fainting — may indicate dangerous blood-pressure drop
- Hives or facial swelling — signs of allergic reaction
- Swelling of ankles or sudden weight gain — potential heart-failure warning
- Any new or worsening back pain — uncommon but reported with tadalafil
Scientific References
- Rajfer J et al. Evaluation of once-daily vs on-demand tadalafil: is there a cumulative effect? Int J Impot Res. 2014.
- Rendón RA et al. Tadalafil once a day for men with ED: superiority over on-demand? Sex Med Rev. 2020.
- Davidson MH et al. Population dose-response model for tadalafil in male ED. Clin Pharmacol Ther. 2004.
- Porst H et al. Comparison of efficacy, safety, and tolerability of on-demand vs daily tadalafil. Urology. 2005.
- Padma-Nathan H et al. Efficacy of tadalafil at 24 and 36 hours after dosing: RCT. J Urol. 2003.
Frequently Asked Questions
Can I split a 20 mg Cialis tablet to make two 10 mg doses?
Yes. Generic tadalafil tablets are not extended-release, so splitting is safe if the pill has a score line. Use a pill cutter for accurate halves and always check with your pharmacist first.
How long should I wait to drink alcohol after taking Cialis?
Moderate alcohol (1–2 drinks) is generally safe, but larger amounts can amplify dizziness and blood-pressure drops. Wait at least 2 hours between the dose and heavy drinking, or skip alcohol altogether on dosing days.
Does food affect how fast Cialis works?
No. Unlike sildenafil, tadalafil’s absorption is not significantly delayed by high-fat meals, so you can take it with or without food.
Is daily Cialis approved for prostate symptoms?
Yes. The 5 mg once-daily dose also treats benign prostatic hyperplasia (BPH) related urinary symptoms, giving some men a dual benefit.
Can I take tadalafil if I use nitroglycerin?
No. Combining any PDE5 inhibitor with nitrates can cause a life-threatening blood-pressure crash. You’ll need an alternative ED treatment.
What if the 10 mg dose isn’t strong enough?
Your provider may increase you to 20 mg on demand or switch you to daily 5 mg for cumulative effect. Never double doses without medical guidance.
Will insurance cover generic tadalafil?
Coverage varies. Many plans cover at least six tablets per month. If you pay cash, Rx.com’s discount card often beats insurance copays.
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