Cialis Side Effects: 10 Facts on Risks and Safety

Cialis side effects are usually mild and short-lived: in the FDA-reviewed trials, the most common were headache, indigestion (dyspepsia), back pain, muscle aches, flushing and a stuffy nose, and most fade within a few hours. Back pain and muscle aches are the exception, typically starting 12–24 hours after a dose and settling within 48 hours. Serious reactions such as an erection lasting more than 4 hours, sudden vision or hearing loss, and dangerous drops in blood pressure with nitrates are rare but need urgent care.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; NHS — Tadalafil

Why Cialis causes side effects

Cialis is the brand name of tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor approved for erectile dysfunction (ED) and for the urinary symptoms of an enlarged prostate (benign prostatic hyperplasia, BPH). It relaxes smooth muscle and widens blood vessels in the penis, so blood can flow in when you are sexually aroused. It does not cause an erection on its own.

The same blood-vessel-widening action happens elsewhere in the body, which explains most side effects. Dilated vessels in the head cause headache and facial flushing, swollen vessels in the nose cause congestion, and relaxed smooth muscle in the gut can lead to indigestion or reflux. Tadalafil and alcohol are both mild vasodilators, which is why they can lower blood pressure together.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; Cleveland Clinic — Phosphodiesterase inhibitors

What makes tadalafil different from other ED pills is how long it stays in the body. Its half-life is 17.5 hours in healthy men, and the label reports improved erections for up to 36 hours after a dose. So side effects and interactions can last longer than with sildenafil. Our Viagra vs Cialis comparison explains these timing differences in detail.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Common Cialis side effects and how often they happen

The US prescribing information pooled eight placebo-controlled studies of Cialis taken as needed for ED. The table shows how often each side effect occurred with each dose, compared with placebo. Only effects reported by at least 2% of men, and more often than with placebo, are listed.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Headache and indigestion clearly increase with dose, so a lower dose is the first lever if they bother you. Even so, headache affected only about one man in seven at the highest dose. In these 12-week studies, 3.1% of men on 10 or 20 mg stopped treatment because of side effects, compared with 1.4% on placebo.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

European figures, which the EAU guidelines reproduce from the EU product information, are somewhat higher: headache 14.5%, dyspepsia 12.3%, back pain 6.5%, myalgia 5.7%, nasal congestion 4.3%, flushing 4.1% and dizziness 2.3%.

Source: EAU Guidelines — Management of Erectile Dysfunction

Less common side effects

Effects reported in under 2% of men (a link to the drug is uncertain) include dizziness, fatigue, nausea, diarrhea, blurred vision and ringing in the ears. In men aged 65 or older who used Cialis as needed, diarrhea was reported more often (2.5%). Changes in color vision were rare, in fewer than 0.1% of men across all studies.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; MedlinePlus — Tadalafil

Back pain and muscle aches: the timing is different

Back pain and muscle aches are the Cialis side effects that most often surprise men, because they do not follow the dose straight away. In clinical pharmacology studies they generally started 12 to 24 hours after dosing and usually resolved within 48 hours. It is typically a diffuse ache in the lower back, buttocks or thighs, worse when lying down.

Most episodes were mild or moderate and cleared without treatment; severe back pain made up fewer than 5% of reports. When men needed relief, acetaminophen (paracetamol) or anti-inflammatory painkillers generally worked. Only about 0.5% of men using Cialis on demand stopped because of back pain or muscle aches, and tests for muscle injury, inflammation or kidney damage found no significant underlying problem.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Daily 5 mg vs on-demand Cialis: side effects compared

Cialis can be prescribed in two ways. On demand, the usual starting dose is 10 mg before sex, adjusted to 5 mg or 20 mg and taken no more than once a day. Once daily, the starting dose is 2.5 mg at about the same time every day, which can be raised to 5 mg; the dose for BPH is 5 mg daily. Because tadalafil is long-acting, a daily low dose keeps a steady level in the blood without peaks from a large single dose.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; EAU Guidelines — Management of Erectile Dysfunction

In the label’s three 12-week daily-dosing studies for ED, side effects at 5 mg daily were headache 6%, dyspepsia 5%, back pain 3%, flushing 3%, nasopharyngitis (cold-like symptoms) 3%, myalgia 2% and nasal congestion 2%. The rate of stopping because of side effects was 4.1% with tadalafil and 2.8% with placebo. Back pain and muscle aches with daily use were generally mild or moderate, with a discontinuation rate below 1%.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Longer-term data point the same way. A 2019 meta-analysis of four randomized trials (1,035 men treated for at least 24 weeks) found that any treatment-emergent side effect was more frequent with on-demand tadalafil than with daily tadalafil, while rates of stopping treatment, back pain, muscle aches, headache, indigestion and cold-like symptoms did not differ significantly. The included studies varied in dose and ED severity, so the finding is modest.

Source: Sex Med (PubMed) — Long-term efficacy and tolerance of tadalafil daily vs on-demand (Zhou et al., 2019)

The trade-off is exposure: with daily dosing, tadalafil is always in your system, which matters if you ever need an emergency nitrate. Men who also have BPH symptoms may benefit from the daily 5 mg dose for both problems.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; EAU Guidelines — Management of Erectile Dysfunction

Serious Cialis side effects (rare but important)

Priapism (an erection that will not go away)

Prolonged erections over 4 hours and priapism (painful erections over 6 hours) have been reported rarely with PDE5 inhibitors. Untreated priapism can permanently damage erectile tissue, so any erection lasting more than 4 hours, painful or not, needs emergency care. Men with sickle cell anemia, multiple myeloma, leukemia or Peyronie’s disease should use Cialis with caution.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; NHS — Priapism (painful erections)

Sudden vision loss (NAION)

Non-arteritic anterior ischemic optic neuropathy (NAION) is a rare stroke of the optic nerve that can cause permanent vision loss. It has been reported in temporal association with all PDE5 inhibitors. Observational studies suggest roughly a two-fold rise in risk shortly after PDE5 inhibitor use, against a background rate of 2.5–11.8 cases per 100,000 men aged 50 and over each year, but a causal link has not been proven. A “crowded” optic disc or previous NAION raises the risk. Stop Cialis and seek care immediately if you lose vision in one or both eyes.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Sudden hearing loss

Sudden decrease or loss of hearing, sometimes with ringing in the ears (tinnitus) and dizziness, has been reported in men taking PDE5 inhibitors including Cialis. It is not known whether the drug causes it. The advice is the same as for vision: stop tadalafil and get prompt medical attention.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; Cleveland Clinic — Phosphodiesterase inhibitors

Low blood pressure and heart events

Tadalafil causes a small fall in blood pressure that most men do not notice. A larger drop, with dizziness or fainting, can happen when it is combined with nitrates, alpha-blockers, other blood pressure medicines or heavy drinking. Heart attack, stroke and sudden cardiac death have been reported after use, mostly in men with existing cardiovascular risk factors and often during or shortly after sex, so it is unclear whether the drug, the sexual activity or the heart disease was responsible.

Allergic reactions, including rare severe skin reactions such as Stevens-Johnson syndrome, have also been reported. Swelling of the face or throat, difficulty breathing or a blistering rash are emergencies.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; MedlinePlus — Tadalafil

Who should not take Cialis: nitrates and riociguat

Two drug groups are absolute contraindications, meaning Cialis must not be taken with them at all:

• Nitrates in any form, taken regularly or occasionally: nitroglycerin (glyceryl trinitrate) tablets, sprays, ointments, pastes or patches, isosorbide mononitrate and isosorbide dinitrate. Recreational “poppers” (amyl nitrite and butyl nitrite) are nitrates too. Tadalafil strengthens their blood-pressure-lowering effect.
• Guanylate cyclase stimulators such as riociguat (Adempas), used for pulmonary hypertension. The combination can also drop blood pressure dangerously.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; MedlinePlus — Tadalafil

The 48-hour nitrate rule

Because tadalafil lasts so long, the label states that if a man who has taken Cialis needs a nitrate in a life-threatening situation, at least 48 hours should have passed since his last dose, and the nitrate should only be given under close medical supervision with blood pressure monitoring. This is why anyone who gets chest pain after taking Cialis should seek emergency care rather than reach for a nitroglycerin spray, and should tell the emergency team when he last took tadalafil.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; MedlinePlus — Tadalafil

The EAU guidelines also list nicorandil, a heart drug that acts as a nitric oxide donor, as contraindicated with PDE5 inhibitors. Cialis is also unsuitable for men in whom sexual activity is inadvisable because of their heart condition, such as unstable angina, severe heart failure or a recent heart attack, and for anyone with a known serious allergy to tadalafil. Severe liver disease is a reason to avoid it, and Cialis must not be combined with other PDE5 inhibitors, including Adcirca (the brand of tadalafil used for pulmonary hypertension).

Sources: EAU Guidelines — Management of Erectile Dysfunction; Cleveland Clinic — Phosphodiesterase inhibitors; DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Interactions: alpha-blockers, CYP3A4 inhibitors and alcohol

Alpha-blockers

Alpha-blockers such as tamsulosin, doxazosin and alfuzosin, often used for prostate symptoms, also widen blood vessels, and the combination can add up to symptomatic low blood pressure or fainting. For ED, the label advises that men should be stable on their alpha-blocker before starting a PDE5 inhibitor, and that the PDE5 inhibitor should start at the lowest dose. The EAU guidelines advise caution but do not forbid the combination.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; EAU Guidelines — Management of Erectile Dysfunction

CYP3A4 inhibitors and grapefruit

Tadalafil is broken down by the liver enzyme CYP3A4. Strong blockers of this enzyme, such as ketoconazole, itraconazole and HIV protease inhibitors like ritonavir, raise tadalafil levels; ritonavir at 200 mg twice daily increased tadalafil exposure by 124%. With these drugs, the on-demand dose should not exceed 10 mg once every 72 hours, and the daily dose should not exceed 2.5 mg. Erythromycin, clarithromycin and grapefruit juice are expected to have a similar effect, and the NHS advises not to drink grapefruit juice while taking tadalafil. Enzyme inducers such as rifampin have the opposite effect and can make Cialis less effective.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; NHS — Tadalafil

Alcohol

Substantial amounts (5 units or more) combined with Cialis can cause a faster heart rate, a drop in standing blood pressure, dizziness and headache. Heavy drinking can also make erections harder to achieve, which works against the medicine. Our guide to how long Viagra lasts covers how food and alcohol affect the shorter-acting sildenafil.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; NHS — Tadalafil

How to reduce Cialis side effects

Most Cialis side effects are manageable with a few practical steps, ideally agreed with your doctor or pharmacist:

• Use the lowest dose that works. Headache and indigestion clearly rise from 5 mg to 20 mg, and the label allows the dose to be lowered for tolerability.
• Ask about daily low-dose tadalafil. At 2.5–5 mg daily, headache and dyspepsia rates in trials were roughly half those seen with on-demand 20 mg.
• Treat back pain simply. Acetaminophen or an anti-inflammatory painkiller was generally effective in trials, if these are safe for you.
• Keep alcohol moderate and avoid grapefruit juice.
• Take no more than one dose a day. The effects can last up to 36 hours, so extra tablets mainly add side effects.
• Be careful with dizziness. If you feel dizzy, wait until it passes before driving.
• Share your full medicines list, including supplements such as St John’s wort, so interactions can be checked.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; NHS — Tadalafil; MedlinePlus — Tadalafil

Buy tadalafil only through a prescription and a licensed pharmacy. The FDA warns that many “natural” sexual enhancement products sold online are likely to be contaminated with dangerous hidden ingredients, so their real dose and interactions are unknown. If side effects persist despite these steps, other options exist; our overview of erectile dysfunction explains the full range of treatments.

Sources: FDA — Sexual Enhancement and Energy Product Notifications; EAU Guidelines — Management of Erectile Dysfunction

When to see a doctor or get urgent care

Call emergency services or go to the nearest emergency department if you have:

• An erection lasting more than 4 hours, painful or not (do not drive yourself).
• Chest pain, shortness of breath, palpitations or fainting during or after sex. Do not take a nitrate if you have used Cialis within the last 48 hours; tell the team when you took it.
• Sudden loss or decrease of vision in one or both eyes.
• Sudden loss of hearing, especially with ringing in the ears or dizziness.
• Swelling of the face, lips, tongue or throat, difficulty breathing, or a blistering or peeling rash.
• A seizure.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; NHS — Tadalafil; NHS — Priapism (painful erections)

Book a routine appointment if headaches, indigestion or back pain are troublesome or do not go away, if you notice blue-tinged or blurred vision. ED itself can be an early sign of heart disease or diabetes, so persistent erection problems deserve a medical check rather than ever-higher doses.

Sources: MedlinePlus — Tadalafil; Cleveland Clinic — Phosphodiesterase inhibitors; EAU Guidelines — Management of Erectile Dysfunction

If you are unsure whether tadalafil is right for you, or its side effects are spoiling the benefit, you can arrange a confidential consultation with our urologist-andrologist via WhatsApp. We review your heart health, medicines and goals, and explain every option for erectile dysfunction treatment, from tablets to longer-term solutions.

FAQs about Cialis side effects

What are the most common Cialis side effects?

The most common Cialis side effects are headache, indigestion, back pain, muscle aches, flushing and a stuffy nose. In US trials of on-demand use, headache affected 11–15% of men versus 5% on placebo, and indigestion 4–10%. Most of these effects are mild and wear off within a few hours, although back pain usually appears later.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

How long do Cialis side effects last?

Headache, flushing and congestion usually go away after a few hours. Back pain and muscle aches typically begin 12 to 24 hours after a dose and resolve within about 2 days. Because tadalafil has a half-life of 17.5 hours, any effect can last longer than with sildenafil. Tell your doctor about side effects that persist.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Does daily Cialis have fewer side effects?

In label trials, daily 2.5–5 mg produced lower rates of headache and indigestion than on-demand 10–20 mg, and a 2019 meta-analysis found fewer overall side effects with daily use after 24 weeks. Specific effects such as back pain and headache did not differ significantly in that analysis, so individual experience varies.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; Sex Med (PubMed) — Long-term efficacy and tolerance of tadalafil daily vs on-demand (Zhou et al., 2019)

Can I drink alcohol with Cialis?

Small amounts are generally acceptable, but 5 or more units of alcohol with Cialis can lower standing blood pressure and cause dizziness, a fast heartbeat and headache. Heavy drinking also makes erections harder to achieve. If you feel dizzy, sit or lie down and avoid driving until it passes.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; NHS — Tadalafil

Why is Cialis dangerous with nitrates?

Both tadalafil and nitrates widen blood vessels, and together they can cause a severe, potentially life-threatening fall in blood pressure. This applies to nitroglycerin sprays, tablets and patches, isosorbide drugs and “poppers”. Because tadalafil is long-acting, doctors wait at least 48 hours after the last dose before giving a nitrate.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; MedlinePlus — Tadalafil

Can Cialis cause permanent damage?

Common side effects are temporary. Permanent harm is rare but possible: untreated priapism can damage erectile tissue, and NAION can cause lasting vision loss, although a direct causal link with PDE5 inhibitors is unproven. That is why an erection beyond 4 hours or sudden vision loss requires immediate care.

Source: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information

Is it safe to take Cialis with tamsulosin?

Often yes, with precautions. Tamsulosin and other alpha-blockers also lower blood pressure, so men should be stable on the alpha-blocker first and start tadalafil at the lowest dose. The label does not recommend combining them specifically for BPH treatment. Your doctor should check your blood pressure and adjust doses.

Sources: DailyMed (FDA label) — CIALIS (tadalafil) tablets prescribing information; EAU Guidelines — Management of Erectile Dysfunction