Viagra vs Cialis Side Effects: Sildenafil and Tadalafil Compared
Sildenafil and tadalafil side effects side by side from the Viagra and Cialis labels: headache, flushing, back pain, vision changes and the nitrate rule. Sourced.
By Julian Caraulani · Last updated
Safety
Below: both labels' trial tables side by side, the rarer warnings both drugs share, the nitrate contraindication, and where to ask a clinician. Generic sildenafil and generic tadalafil tablets carry the same labeling as the brands. We do not give doses.
Sildenafil vs tadalafil side effects (label tables)
Viagra figures are from Table 2 of its label (flexible-dose, placebo-controlled trials, the way the drug is normally taken). Cialis figures are from Table 1 of its label (as-needed use, eight placebo-controlled trials of 12 weeks, highest strength tested). Each label lists only effects seen in at least 2% of men and more often than on placebo, so a dash means that label's table does not list it.
| Side effect | Viagra | Placebo | Cialis | Placebo | Source |
|---|---|---|---|---|---|
| Headache | 16% | 4% | 15% | 5% | Viagra label, revised 11/2023; Cialis label, revised 3/2026 |
| Flushing | 10% | 1% | 3% | 1% | Same labels |
| Dyspepsia (indigestion) | 7% | 2% | 10% | 1% | Same labels |
| Nasal congestion | 4% | 2% | 3% | 1% | Same labels |
| Abnormal vision | 3% | 0% | not listed | not listed | Viagra Table 2 |
| Back pain | 2% | 2% | 6% | 3% | Same labels |
| Myalgia (muscle aches) | not listed | not listed | 3% | 1% | Cialis Table 1 |
| Pain in limb | not listed | not listed | 3% | 1% | Cialis Table 1 |
| Dizziness | 2% | 1% | not listed | not listed | Viagra Table 2 |
| Rash | 2% | 1% | not listed | not listed | Viagra Table 2 |
| Stopped because of side effects | 2.5% | 2.3% | 3.1% | 1.4% | Same labels |
The trials were run separately, so the two columns are not a head-to-head comparison. Both labels warn that rates from different trials "cannot be directly compared".
What the differences mean
Vision. Viagra's label describes its vision effect as "predominantly color tinge to vision, but also increased sensitivity to light or blurred vision" (DailyMed: Viagra label). On Cialis, "reports of changes in color vision were rare", under 0.1% of patients across all studies (DailyMed: Cialis label).
Back pain and muscle aches. This is the tadalafil side effect. Its label says "back pain or myalgia generally occurred 12 to 24 hours after dosing and typically resolved within 48 hours" (DailyMed: Cialis label).
Overall. One network meta-analysis pooled "72 trials (20 325 patients) for adverse event analysis". At each drug's usual starting strength, sildenafil "had the highest rate of overall adverse events" and tadalafil "had the lowest overall rate of all adverse events", while sildenafil scored highest on efficacy (Chen et al., Eur Urol 2015, PubMed). That is a trade-off, not a verdict for any one man.
How long effects last. Tadalafil stays in the body much longer than sildenafil, which is why a side effect from it can turn up the next day. The labels give the timing; your prescriber can explain what it means for you.
- FDA-approved and compounded
- No FDA warning letter found
- No state list published
Rare but serious: what both labels warn about
Both drugs carry the same class warnings for PDE5 inhibitors.
- Sudden vision loss. NAION is "a rare condition and a cause of decreased vision including permanent loss of vision, that has been reported rarely post-marketing in temporal association with the use of all PDE5 inhibitors" (DailyMed: Viagra label). MedlinePlus adds: "It is not known if the vision loss was caused by the medication." (MedlinePlus: sildenafil)
- Sudden hearing loss. Both labels tell patients to stop and get prompt care if hearing drops suddenly.
- Prolonged erection. "In the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance." (DailyMed: Viagra label)
- Low blood pressure with other drugs. Both labels warn about alpha-blockers and blood pressure medicines, and the Cialis label about substantial amounts of alcohol.
The nitrate contraindication
This is the one hard rule on both labels. Viagra's label says "VIAGRA was shown to potentiate the hypotensive effect of nitrates" and lists nitrates as a contraindication (DailyMed: Viagra label). The Cialis label says "Administration of CIALIS to patients using any form of organic nitrate is contraindicated" and, for an emergency, "at least 48 hours should elapse after the last dose of CIALIS before nitrate administration is considered" (DailyMed: Cialis label). Nitrates include nitroglycerin for chest pain, and the patient leaflets also name "poppers". Any online intake should ask about them; if one does not, that is a red flag.
What the videos show
Urologists, pharmacists and men who take these pills compare them on YouTube. Treat these as individual accounts and opinions, not evidence: one person's headache or back pain says nothing about how often it happens. Our sildenafil and tadalafil video hub has the full list.
Everything you need to know about Sildenafil vs Tadalafil for erectile dysfunction | ED pillsRena Malik, M.D., December 3, 2021
Urologist Explains How to Use Tadalafil vs Sildenafil the Right WayRena Malik, M.D., April 29, 2023
Are Viagra and Cialis Really Harmful to Your Heart? | UroChannelUroChannel, April 5, 2023
Videos belong to their channels; our summary is on each video's page. All 8 Sildenafil and tadalafil videos.
Which programs let you message a clinician
Side effects are the main reason to switch drugs or strengths, and that is the prescriber's call. This table shows which ED programs let you message a clinician after the visit, from each program's own pages.
| Program | Message a clinician | Cost | Lowest price |
|---|---|---|---|
| Strut Health | Yes: Free, unlimited follow-ups with a healthcare provider, who you can message from your account. source, 2026-10-31 | Included | $16 |
| GoodRx Care | Yes: You message your provider from the treatment subscription dashboard; a dose change or a long gap may require a new paid telehealth visit, and no messaging price is stated. source, 2026-10-31 | Not stated | $18 |
| BlueChew | Yes: You can message the BlueChew medical team through your account; the page does not say whether it costs anything. source, 2026-10-31 | Not stated | $20 |
| Hims | Yes: You can message a provider with questions at any time, for free. source, 2026-10-31 | Included | $22 |
| Ro | Yes: Free, unlimited follow-up messaging with a Ro-affiliated provider after you start treatment. source, 2026-10-31 | Included | $32 |
| Maximus | Yes: Every protocol includes 24/7 messaging with your care team at no additional cost. source, 2026-10-31 | Included | $35.99 |
| Henry Meds | Yes: You and your provider exchange messages in a secure patient portal, and ongoing care is part of the plan price. source, 2026-10-31 | Included | $50 |
| MangoRx | Yes: Unlimited access to licensed providers for any concerns, with ongoing provider support listed in the monthly plan; the page does not name the channel. source, 2026-10-31 | Included | $59 |
| Rex MD | Yes: Follow-ups are free once treatment starts; you message your assigned provider through the member portal any time. source, 2026-10-31 | Included | $18 |
| Lemonaid Health | Yes: Messaging with clinical providers is included (stated on the oral minoxidil hair loss page; the ED page does not mention it). source, 2026-10-31 | Included | See review |
| PeterMD | Yes: Unlimited free consultations and 24/7 access to your medical team; the page says access and consults, not messaging by name. source, 2026-10-31 | Included | See review |
| Hone Health | Yes: Unlimited messaging with your care team, plus a clinician meeting every 3 months, as part of the membership. source, 2026-10-31 | Included in the paid Hone membership | See review |
| Rugiet | Yes: You can message your doctor anytime in the portal, and unlimited follow-ups with your doctor are included in the price. source, 2026-10-31 | Included | $99 |
| DudeMeds | Not found: No statement found on the site about messaging a clinician after starting treatment. | Not stated | See review |
From each program's own page, read 2026-10-31.
What it costs
Both generics are cheap. Generic sildenafil starts at $1.60 a dose at Strut Health, and generic tadalafil at $1.80 a dose at Rex MD, visit included, as checked October 31, 2026. Every plan is on our generic sildenafil price page and generic tadalafil price page, and the overall ranking is on Best men's health programs.
Questions
FAQ
Which has fewer side effects, Viagra or Cialis?
In their own trials, headache was about as common on both. Sildenafil showed more flushing and vision changes; tadalafil more indigestion, back pain and muscle aches. A 2015 network meta-analysis found the lowest overall rate of side effects with tadalafil and the highest with sildenafil, at usual starting strengths.
What is the most common side effect of sildenafil?
Headache: 16% of men vs 4% on placebo in the Viagra label's flexible-dose trials. Flushing (10% vs 1%) and indigestion (7% vs 2%) come next.
Why does tadalafil cause back pain?
The label does not give a mechanism. It says back pain or muscle aches usually appeared 12 to 24 hours after a dose and typically resolved within 48 hours, mostly mild or moderate.
Can sildenafil change your vision?
Yes, usually briefly. The Viagra label describes a color tinge, light sensitivity or blurred vision, in 3% of men vs 0% on placebo in flexible-dose trials. Sudden vision loss is rare and needs urgent care.
Can you take an ED pill with nitrates?
No. Both labels list nitrates as a contraindication because the combination can drop blood pressure dangerously. Tell the prescriber about every heart medicine.
Do generic sildenafil and tadalafil have the same side effects?
Yes. FDA-approved generics carry the same labeling as Viagra and Cialis. Chewables, mints and drops are a separate group: they are compounded, and their forms are not reviewed by the FDA.
What should I do if a side effect bothers me?
Message the prescriber. Switching drugs or strengths is their decision, and most programs in the table above let you message a clinician.