Sildenafil vs Tadalafil: The Real Differences That Matter

Reviewed by LPMD Medical Group cliniciansUpdated 2026-09-135 min read

The short answer

Sildenafil and tadalafil both treat erectile dysfunction by blocking the PDE5 enzyme, and both are inexpensive generics. Sildenafil is taken about an hour before sex, is slowed by a high-fat meal, and works for roughly 4 to 5 hours; tadalafil is unaffected by food, can work for up to 36 hours, and is the only one approved as a low daily dose. Neither works without arousal, and neither may ever be combined with nitrates.

Every ranch has two reliable horses. One is quick out of the gate and back in the barn by supper. The other takes a minute to get going, then carries you clear through to tomorrow’s breakfast. Sildenafil and tadalafil are those two horses, and the internet has loud opinions about which one you should saddle.

Here is what nobody selling a subscription mentions: they are cousins. Same drug class, same basic job, same hard safety rules. The differences are real, but they come down to timing, food and side-effect flavor, not to one being “stronger” in any way that matters for most men.

We all need a little help getting hung sometimes. Picking the right help is the part worth thinking about.

Key facts

Sildenafil and tadalafil are both PDE5 inhibitors: they help blood flow into the penis during arousal and do nothing without it ¹²³.
Sildenafil is taken about 1 hour before sex (30 minutes to 4 hours), and a high-fat meal delays it by about an hour ¹².
Tadalafil can be taken with or without food and improved erections for up to 36 hours after a dose in its trials ³.
Tadalafil is also approved as a low daily dose of 2.5 to 5 mg; sildenafil is as-needed only ¹³.
Both are generics, and neither may ever be combined with nitrates, poppers or riociguat ¹³⁸.
Common side effects overlap (headache, flushing, indigestion); sildenafil adds vision changes, tadalafil adds back pain and muscle aches ²³.

How are sildenafil and tadalafil different?

They are close chemical relatives with very different half-lives, and that one number drives almost everything else. Sildenafil’s half-life is about 4 hours, so most of it is gone by the next morning ². Tadalafil’s is 17.5 hours, which is why a single dose can still be working a day and a half later ³.

Both block phosphodiesterase type 5, the enzyme that winds an erection down, and both need you to be turned on for anything to happen. Sildenafil’s label says it plainly: at recommended doses it has no effect in the absence of sexual stimulation ². Tadalafil’s label says the same thing, and MedlinePlus adds that it does not increase sexual desire ³⁵.

How fast do they work and how long do they last?

Sildenafil is quicker to peak and quicker to fade; tadalafil is the long rider. The sildenafil label says to take 50 mg about 1 hour before sex, anywhere from 30 minutes to 4 hours ahead ¹. MedlinePlus gives the same window, and Mayo Clinic says the effects often last 4 to 5 hours ⁴⁶.

Tadalafil is usually taken at least 30 minutes before sex, and in the label’s trials it improved erections compared with placebo up to 36 hours after a dose ³⁵. Nobody has a 36-hour erection; the drug keeps the door open that long if the mood arrives.

Food is the other split. A high-fat meal slows sildenafil’s absorption, delaying its peak by about 60 minutes and lowering it by 29 percent ². Tadalafil’s label says it may be taken without regard to food ³. Mayo Clinic notes the body also takes longer to absorb sildenafil after alcohol, and heavy drinking works against erections all on its own ⁶.

	Sildenafil	Tadalafil
Doses	25, 50 or 100 mg as needed ¹	5 to 20 mg as needed, or 2.5 to 5 mg daily ³
Take it	About 1 hour before; 30 minutes to 4 hours ¹	At least 30 minutes before, or once daily ³⁵
Window	About 4 to 5 hours ⁶	Up to 36 hours ³
Half-life	About 4 hours ²	17.5 hours ³
Food	High-fat meal delays it about 1 hour ²	No food effect ³
Maximum	Once per day ¹	Once per day ³

Can tadalafil be taken every day?

Yes, and it is the only one of the two with an approved daily dose. The tadalafil label lists 2.5 mg once daily as the starting dose for erectile dysfunction, with an increase to 5 mg if needed, and 5 mg daily for men who also have an enlarged prostate ³. Steady levels build within about 5 days ³. Sildenafil is labeled for as-needed use only ¹.

If watching the clock kills the mood for you, that difference alone can settle the question. We weigh the trade-offs in our daily versus as-needed tadalafil article.

Which has fewer side effects?

Neither wins outright; they trade one annoyance for another. In sildenafil’s fixed-dose trials, headache affected 16 to 28 percent of men depending on dose (7 percent on placebo), flushing 10 to 19 percent, indigestion 3 to 17 percent, and vision changes 1 to 11 percent, most common at 100 mg ².

Tadalafil’s as-needed trials reported headache in 11 to 15 percent (5 percent on placebo), indigestion in 4 to 10 percent, back pain in 3 to 6 percent and muscle aches in 1 to 4 percent ³. The back and muscle pain tend to start 12 to 24 hours after a dose and clear within 48 hours ³. Because tadalafil lingers, its side effects can too. A 2013 network meta-analysis of 118 trials in more than 31,000 men found no major difference in safety among the PDE5 inhibitors and ranked tadalafil most effective, followed by vardenafil ⁷.

The serious warnings are identical: an erection lasting more than 4 hours, sudden loss of vision or hearing, and a dangerous blood pressure drop with nitrates or poppers ¹³⁴⁵.

What do sildenafil and tadalafil cost?

Both have been generic for years, so the branded version is rarely worth the markup. FDA requires a generic to carry the same active ingredient, strength, dosage form and route as the original, and notes that prices fall about 30 percent with one generic competitor and nearly 85 percent with five ⁸. Both molecules have far more than five. Retail pharmacy prices still vary by dose and quantity. Through Hung, every compounded option costs the same, from $35 a month for three months to $20 a month for twelve, consult included.

Who tends to prefer which?

Men who plan tend to like sildenafil; men who would rather not plan tend to like tadalafil. Sildenafil suits a man who wants a predictable window, a lighter dinner, and side effects that are gone by morning ¹²⁶. Tadalafil suits a man who wants a weekend rather than an appointment, who also has prostate symptoms, or who takes the low daily dose so the question never comes up ³⁶.

Some men switch and switch back. That is allowed. What is not allowed is taking both, or doubling up because the first pill seemed slow; both labels say combinations of PDE5 inhibitors have not been studied and are not recommended ¹³. See the sildenafil page for how we prescribe it, and the tadalafil page for its daily and as-needed options.

When to talk to a clinician

Get emergency care for an erection lasting more than 4 hours, sudden vision or hearing loss, chest pain during sex, or fainting ¹³. Never take either medicine if you use nitroglycerin, isosorbide or any other nitrate, poppers, or riociguat ¹³. Tell your clinician about alpha-blockers, blood pressure medicines, antifungals and HIV medicines, because those change the safe starting dose ¹³.

Also check in first if you have had a heart attack or stroke in the past 6 months, have uncontrolled blood pressure, or have serious kidney or liver disease ⁶. Trouble with erections can be an early sign of trouble with the heart, and a clinician should know about both.

Two good horses, one plan with the consult included, and a clinician who will help you pick the right one for the ride you have in mind.

Hard questions, straight answers

Is tadalafil stronger than sildenafil?

Not in the way most men mean. Both reliably beat placebo in trials, and a 2013 network meta-analysis of 118 trials found no major difference in safety, with tadalafil ranking most effective by a small margin. The real difference is duration: tadalafil can work for up to 36 hours, sildenafil for roughly 4 to 5.

Can I take sildenafil and tadalafil together?

No. Both labels say combinations of PDE5 inhibitors have not been studied and are not recommended. Take one medicine, at one dose, no more than once a day, and never with nitrates or poppers.

Does food affect tadalafil like it affects sildenafil?

No. A high-fat meal delays sildenafil's peak by about an hour and lowers it by about 29 percent, so the label suggests taking it on a lighter stomach. Tadalafil's label says it may be taken without regard to food.

Which is cheaper, sildenafil or tadalafil?

Both are generic and both are inexpensive compared with the branded originals. Pharmacy prices vary by dose and quantity, so the honest answer is to compare the specific prescription you would actually fill. Through Hung, every medicine costs the same: $35 a month for a three-month plan down to $20 a month for twelve, consult included.

How long does sildenafil last compared with tadalafil?

Sildenafil's half-life is about 4 hours and its effects often last 4 to 5 hours. Tadalafil's half-life is 17.5 hours, and in its trials it improved erections compared with placebo up to 36 hours after a dose. Neither causes an erection for that whole time; they keep the door open while you are aroused.

Sources

Information checked 2026-09-13 by LPMD Medical Group clinicians. This article is general education, not a diagnosis or a treatment plan for you. Your clinician and pharmacist provide the instructions for your actual prescription.