Sildenafil (generic Viagra) comes in three strengths: 20mg, 50mg, and 100mg. You might assume bigger is better, but dosing is more nuanced than that. The right dose depends on your health profile, other medications, and how you respond. Here’s how doctors think about it.
The Standard Starting Dose: 50mg
For most men, 50mg is the recommended starting dose.[1] This is the Goldilocks approach—strong enough to be effective for the majority of patients, while keeping side effects manageable. Take it approximately 30–60 minutes before sexual activity, ideally on an empty stomach.
When 25mg Makes Sense
Your doctor might start you at a lower dose if you:[1]
- Are over 65 (sildenafil clearance decreases with age)
- Have liver impairment
- Have kidney impairment
- Take CYP3A4 inhibitors (certain antifungals, HIV protease inhibitors)
- Take alpha-blockers for prostate or blood pressure
The pharmacokinetic reason: sildenafil is metabolized primarily by the liver enzyme CYP3A4. Anything that slows this enzyme raises sildenafil levels in your blood, making a lower dose act like a higher one.[3]
The 20mg Question: Pulmonary Hypertension vs ED
Here’s something that confuses many patients: sildenafil 20mg tablets are FDA-approved for pulmonary arterial hypertension (PAH), not ED. The brand name for that indication is Revatio. However, some prescribers write sildenafil 20mg prescriptions for ED because they’re cheaper—insurance that won’t cover “Viagra” might cover “sildenafil 20mg for off-label use.”
If your doctor prescribes 20mg for ED, they typically instruct you to take multiple tablets (e.g., two or three 20mg tablets for a 40mg or 60mg dose). This is a cost-saving strategy, not a clinical recommendation for a 20mg ED dose.
When to Move Up to 100mg
The maximum recommended dose is 100mg, not to be taken more than once per day.[1] Your doctor may increase your dose if:
- 50mg was partially effective but not fully satisfactory
- You tolerated 50mg well with minimal side effects
- You don’t have risk factors for lower dosing
It might be tempting to double up if one pill didn’t work perfectly. Don’t. About 30–35% of men don’t respond to PDE5 inhibitors at any dose. Taking more won’t fix a non-response—it’ll just increase side effects. Talk to your prescriber about adjusting dose or switching medications.
Timing Matters as Much as Dose
Before concluding your dose is too low, check your timing:
- Empty stomach: A high-fat meal can delay absorption by an hour or more and reduce peak levels[1]
- 30–60 minute window: Sildenafil peaks at about 60 minutes. Taking it 10 minutes before and expecting results is a timing problem, not a dose problem
- Sexual stimulation required: Sildenafil enhances the natural arousal process. It doesn’t create arousal from scratch
The Cost Advantage of Correct Dosing
Generic sildenafil pricing through telehealth providers often makes higher doses cheaper per milligram than lower ones. Some providers offer 20 tablets of sildenafil for under $40, regardless of strength. Getting the right dose from the start means you’re not wasting pills experimenting on your own.
A licensed provider can determine your optimal sildenafil dose based on your health profile. No guesswork needed.
Find a Provider →The Bottom Line
Start at the dose your doctor recommends—usually 50mg. Give it at least 4–6 attempts with proper timing before concluding it’s not working. If 50mg is partially effective, 100mg may be the answer. If it’s doing nothing at all, a higher dose likely won’t help—you need a different medication or a different approach.