Sildenafil comes in 25mg, 50mg and 100mg, and the question of which one you should be on gets more attention than it deserves, because the answer is a rule rather than a number: the lowest strength that reliably works for you. What that rule means in practice — who starts where, how the doses actually differ, when to step up or down, and how to handle the transition — is what this guide covers. It's written for men who want to understand their prescription, not to adjust it without a prescriber.
How the Three Strengths Differ
| 25mg | 50mg | 100mg | |
|---|---|---|---|
| Role | Low starting dose; reduced dose for specific groups | Standard starting dose | Step-up dose after partial response to 50mg |
| Typical onset | 30–60 min | 30–60 min | 30–60 min (same) |
| Strength of effect | Lower | Adequate for most men | Strongest |
| Duration | ~4 hrs | ~4–5 hrs | ~5–6 hrs |
| Side effects | Least | Moderate | Most; blue vision more likely |
| Who | Over 65, liver/kidney impairment, interacting meds, side-effect sensitive | Most men, first prescription | Men with inadequate response to 50mg after a fair trial |
| Roman price (Sep 2026) | ~$4/dose | ~$6/dose | ~$10/dose |
Two things worth noticing. First, onset doesn't change with dose; a higher dose is a stronger effect, not a faster one. Second, side effects scale with milligrams as reliably as effect does, which is the whole reason the “lowest effective dose” rule exists.
Where Most Men Start: 50mg
For a healthy man under 65 with no interacting medications, 50mg is the standard starting point. It's enough for the majority of men, and it gives a clear read: if it works well, you've found your dose; if it works partly, 100mg is the next step; if it works too well or with bothersome side effects, 25mg is worth trying. The starting dose is set in your evaluation. Roman's process — medical history, blood pressure reading, video visit with a licensed clinician — is where that decision gets made, and it's the right place to mention any medication, condition or previous experience with ED drugs that might shift it.
When 25mg Is the Right Start
Clinicians start lower in specific situations:
- Age over 65: sildenafil is cleared more slowly, so a given dose produces higher blood levels.
- Liver or kidney impairment: same reason.
- Interacting medications: drugs that inhibit the liver enzyme CYP3A4 — certain antifungals (ketoconazole, itraconazole), antibiotics (erythromycin, clarithromycin) and HIV protease inhibitors — raise sildenafil levels substantially. Alpha-blockers add to the blood pressure effect. A lower dose is standard alongside any of these.
- Side-effect sensitivity: men who know they react strongly to medications, or who found 50mg's headache or flushing unpleasant.
Starting at 25mg isn't a judgment that your ED is mild; it's a safety margin. Many men in these groups step up to 50mg after a few doses.
Get Sildenafil at the Right Strength Through Roman →25, 50 and 100mg · Clinician-set · Easy to adjustWhen to Step Up to 100mg
The move from 50mg to 100mg is common and appropriate when, after a fair trial of 50mg with correct timing, the response is real but not enough. “Fair trial” matters: several attempts on separate days, taken an hour ahead on a light stomach with limited alcohol. A single disappointing night after a heavy dinner isn't a reason to double the dose; it's a reason to fix the timing. See Sildenafil Didn't Work? What to Do Next.
Expect 100mg to bring a stronger, somewhat longer effect and a higher chance of headache, flushing and the bluish visual tint. If 100mg works but the side effects are a problem, that's a conversation about switching to tadalafil rather than pushing through. And 100mg is the ceiling: there's no 150mg, and taking more than 100mg in 24 hours isn't more effective, just riskier.
When to Step Down
Less discussed but just as legitimate. If 50mg works fully and you get side effects, try 25mg; many men find it sufficient with noticeably less headache. If 100mg works fully, ask whether 50mg would too. Response can also improve over time as anxiety drops and technique settles, so a dose that was necessary at first may be more than you need later. Side effect detail: Sildenafil Side Effects: What to Actually Expect.
Tablet Splitting
What Never Changes With Dose
- Once per 24 hours, maximum. At any strength.
- Stimulation required. 100mg doesn't create an erection either; it makes one easier in response to arousal.
- The nitrate contraindication. Absolute at 25mg, absolute at 100mg.
- Onset. About an hour, less on an empty stomach, more after a heavy meal, regardless of strength.
Making a Change
Every strength change is a prescription change. That's not bureaucracy; it's the mechanism by which someone with your medical history checks that the new dose is sensible alongside everything else you take. Roman's model includes clinician messaging after your initial prescription, so moving from 50mg to 100mg or down to 25mg is a message and a plan update, not a new evaluation. If you buy fixed packs from a provider like PeterMD, which sells 100mg only, the strength conversation happens with its reviewing provider, including any question about splitting.
Our Verdict — September 2026
Start at 50mg unless there's a specific reason to start at 25mg. Move to 100mg only after a proper trial of 50mg falls short. Move down whenever a lower dose works. The right strength is the one that reliably works with the fewest side effects, and it's found by adjustment with a prescriber rather than guesswork. Roman's evaluation sets the starting point and its clinician messaging makes the adjustments easy.
Frequently Asked Questions
What is the normal starting dose of sildenafil?
50mg for most men. Clinicians may start at 25mg for men over 65, men with liver or kidney impairment, or men on medications that raise sildenafil levels. 100mg is generally a step up after 50mg, not a starting point.
Is 100mg sildenafil twice as strong as 50mg?
Not exactly. The effect increases with dose but not in a straight line; 100mg gives a stronger and somewhat longer effect than 50mg for men who need it, at the cost of more side effects. For men who respond fully to 50mg, 100mg adds side effects without benefit.
Can I take two 50mg tablets instead of one 100mg?
Only if your prescriber has told you your dose is 100mg. Two 50mg tablets is the same dose as one 100mg, but the decision to be on 100mg is a clinical one, not a math one.
Can I split a 100mg tablet to make 50mg?
Some prescribers approve this, particularly with scored tablets, and it can be practical. Unscored tablets split unevenly. Ask before doing it; don't assume.
Does a higher dose work faster?
No. Onset is governed by absorption, which depends on food and formulation. A higher dose produces a stronger effect at the same time, not an earlier one.
What's the maximum sildenafil dose?
100mg is the maximum recommended dose, taken no more than once in 24 hours. Higher doses aren't more effective and raise the risk of side effects and adverse events.
Why did my clinician start me on 25mg?
Common reasons: age over 65, reduced liver or kidney function, or a medication like certain antifungals, antibiotics, HIV drugs or alpha-blockers that interacts with sildenafil. Starting low and stepping up is standard practice in those situations.