# Tadalafil side effects: what the label lists, including back pain > The most common tadalafil side effects are headache, indigestion, back pain, muscle aches, flushing and a stuffy nose. In the Cialis label's as-needed trials, headache affected 11% to 15% of men against 5% on placebo. Back pain and aches usually start 12 to 24 hours after a dose and fade within 48 hours. _Last updated: 2026-10-17_ --- Status: FDA-approved prescription medicine for ED. Source: Cialis prescribing information (Eli Lilly), DailyMed, checked 2026-10-17. **In short:** tadalafil, sold under the brand name Cialis and as generics, shares its core side effects with sildenafil, another pill in its class (headache, indigestion, flushing, a stuffy nose), plus one it is better known for: back pain and muscle aches that tend to arrive the day after a dose. The FDA label's most common list is headache, indigestion (dyspepsia), back pain, muscle aches (myalgia), nasal congestion, flushing and pain in the arms or legs ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). Serious events are rare, and they are worth knowing by name. Evidence level: approved drug, labeled use, backed by clinical trials in more than 9,000 men, including placebo-controlled trials, and the manufacturer's post-marketing reports. ## What are the most common side effects of tadalafil? The most common tadalafil side effects are headache, indigestion, back pain, muscle aches, a stuffy nose, flushing and aching arms or legs. In the eight placebo-controlled trials of as-needed use summarized on the Cialis label, each of these was reported by at least 2% of men on the higher strengths and more often than on placebo; the rates below are the range across the strengths tested ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). | Side effect (as-needed trials) | Tadalafil, range across strengths | Placebo | | ------------------------------ | --------------------------------- | ------- | | Headache | 11% to 15% | 5% | | Indigestion (dyspepsia) | 4% to 10% | 1% | | Back pain | 3% to 6% | 3% | | Muscle aches (myalgia) | 1% to 4% | 1% | | Nasal congestion | 2% to 3% | 1% | | Flushing | 2% to 3% | 1% | | Pain in arms or legs | 1% to 3% | 1% | Source: Table 1 of the [Cialis prescribing information](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895), eight trials of 12 weeks, mean age 59. In these trials, 3.1% of men on tadalafil stopped because of side effects, against 1.4% on placebo. This page reports what the trials measured; it does not recommend a strength. Choosing one is the prescriber's call, and the label lowers it for some men, for example those with kidney or liver problems. The placebo column matters as much as the drug column: some men on a dummy pill report headaches and back pain too. Our guide to [reading ED evidence](/how-to-read-ed-evidence/) explains how to read a side-effect table against its placebo row. ## Why does tadalafil cause side effects at all? Tadalafil's side effects are tied to how it works. It blocks PDE5, an enzyme that breaks down cGMP, the chemical signal that relaxes smooth muscle and lets more blood flow into the penis. The label notes PDE5 is found not only in penile tissue but in blood vessels, skeletal muscle, platelets and many other organs ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). The label also describes tadalafil as a mild vasodilator, meaning it widens blood vessels, which is why it can lower blood pressure, especially when combined with alcohol, nitrates or some blood pressure medicines. Our explainer on [how ED medications work](/how-ed-medications-work/) walks through the whole chain from arousal to the pill. ## Why can tadalafil cause back pain and muscle aches? Nobody has pinned down exactly why, but the pattern is well described, and testing has not found a medically significant underlying cause. The label says that in tadalafil's clinical pharmacology trials, back pain or muscle aches generally began 12 to 24 hours after a dose and typically resolved within 48 hours. Men described a diffuse ache on both sides of the lower back, buttocks, thighs or mid-back that got worse lying down, usually mild or moderate and gone without treatment ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). A three-part study published in 2005 pooled 10 placebo-controlled trials and found back pain or muscle aches in 8.3% to 9.4% of men on tadalafil against 3.7% on placebo. In healthy volunteers, blood markers of inflammation and muscle damage did not change much, and PET and MRI scans showed no muscle inflammation in the lower back or buttocks. The authors concluded the mechanism "remains unknown" but the events appear "self-limiting" ([Seftel et al., Int J Impot Res 2005](https://pubmed.ncbi.nlm.nih.gov/16034469/)). The label adds a few useful numbers: - **Severity:** severe back pain made up fewer than 5% of all back-pain reports. - **Stopping:** about 0.5% of men taking tadalafil as needed stopped because of back pain or muscle aches. - **Testing:** checks for inflammation, muscle injury or kidney damage found no medically significant underlying cause. - **Another enzyme:** tadalafil also partly blocks PDE11, found in skeletal muscle, but the label says the clinical consequence of that in humans "has not been defined." The label notes that when men in the trials did need treatment for the ache, common pain relievers were generally effective. Check with a pharmacist or prescriber before adding any medicine, since some pain relievers are not right for everyone. ## Does tadalafil cause headaches? Yes. Headache is the single most common tadalafil side effect, reported by 11% to 15% of men in the as-needed trials against 5% on placebo ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). The Cialis patient information says the common side effects usually go away after a few hours. Alcohol can add to it. The label warns that heavy drinking (5 or more units) together with tadalafil can raise the chance of headache, dizziness, a faster heartbeat and a drop in blood pressure on standing, because both widen blood vessels. Migraine appears in the label's post-marketing list. ## Does tadalafil cause heartburn or indigestion? Indigestion is the second most common tadalafil side effect in the as-needed trials, and acid reflux shows up in the daily-use trials. The label's as-needed trials counted dyspepsia in 4% to 10% of men against 1% on placebo, and the daily-use trials also recorded gastroesophageal reflux disease (acid reflux) in 1% to 2% of men against none on placebo ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). MedlinePlus, the National Library of Medicine's drug guide, lists "indigestion or heartburn" among the effects to mention to your doctor if they are severe or do not go away ([MedlinePlus: Tadalafil](https://medlineplus.gov/druginfo/meds/a604008.html)). Diarrhea is less common. Across the as-needed trials it was reported more often in men 65 and older, at 2.5%. ## Do side effects differ with daily tadalafil? The same kinds of side effects appear with once-daily tadalafil, and in the label's tables the rates are similar to or lower than in the as-needed trials. In the label's 12-week daily-use trials for ED, the side effects seen more often than on placebo included indigestion, back pain, upper respiratory infection, cough, flushing and muscle aches ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). | Side effect (daily-use ED trials, 12 weeks) | Tadalafil, range across strengths | Placebo | | ------------------------------------------- | --------------------------------- | ------- | | Headache | 3% to 6% | 5% | | Indigestion | 4% to 5% | 2% | | Back pain | 3% | 1% | | Upper respiratory infection | 3% | 1% | | Flushing | 1% to 3% | 1% | | Muscle aches | 2% | 1% | | Cough | 2% to 4% | 0% | Source: Table 2 of the [Cialis prescribing information](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895). In the daily-use ED trials, 4.1% of men on tadalafil stopped because of side effects, against 2.8% on placebo, and the label says back pain and aches were generally mild or moderate, with fewer than 1% stopping for them. Daily use keeps a steady level of the drug in the body, which the label says prescribers should weigh when checking for interactions. ## Does tadalafil affect your vision? A change in color vision is rare with tadalafil, reported in fewer than 0.1% of men across all its trials ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). The labels link color effects to blocking PDE6, an enzyme the retina uses to process light. The Cialis label puts tadalafil at 700 times more potent for PDE5 than for PDE6. The Viagra label puts sildenafil at only about 10 times, and says this lower selectivity is thought to be the basis for sildenafil's color-vision effects, which subjects described as trouble telling blue from green ([Viagra prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0b0be196-0c62-461c-94f4-9a35339b4501)). A brief color tint is a different thing from sudden loss of vision, which is rare and needs urgent care, as the next section explains. ## Which tadalafil side effects need urgent care? A few rare effects need emergency or prompt care. The first four rows come from the label ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)); the last comes from MedlinePlus ([MedlinePlus: Tadalafil](https://medlineplus.gov/druginfo/meds/a604008.html)): | Sign | What the source says to do | | ------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------- | | An erection lasting more than 4 hours, painful or not | Seek emergency care; untreated priapism can permanently damage erectile tissue | | Sudden loss of vision in one or both eyes | Stop all PDE5 pills and seek medical attention; it can be a sign of NAION, a rare optic nerve problem | | Sudden decrease or loss of hearing, sometimes with ringing or dizziness | Stop the drug and seek prompt medical attention | | Chest pain after taking tadalafil | Seek immediate medical attention and tell staff you took tadalafil, because nitrates are not given for a period afterward | | Hives, swelling of the face or throat, trouble breathing, blistering or peeling skin | MedlinePlus lists these as serious: call a doctor immediately or get emergency treatment | On NAION, the label cites published estimates of 2.5 to 11.8 cases per 100,000 men aged 50 and over each year, and an observational study that found about a twofold higher risk within five half-lives of taking a PDE5 inhibitor. The label states that neither the post-marketing reports nor these studies establish that the drugs cause NAION. That study, whose first author was at Pfizer, estimated that weekly use adds three cases per 100,000 men aged 50 and over each year ([Campbell et al., J Sex Med 2015](https://pubmed.ncbi.nlm.nih.gov/25358826/)). In the post-marketing reports, most but not all men who developed NAION already had risk factors such as a "crowded" optic disc, age over 50, diabetes, high blood pressure, coronary artery disease, high cholesterol or smoking. Heart events need the same context. The label records post-marketing reports of heart attack, sudden cardiac death and stroke in men taking tadalafil, most but not all in men with existing cardiovascular risk factors and many during or shortly after sex, and states it is not possible to tell whether the drug, sexual activity or the underlying disease was responsible. For the same emergencies across the whole drug class, see our guide to [ED medication side effects](/ed-medication-side-effects/). Never combine tadalafil with nitrates (such as nitroglycerin) or with riociguat: the label lists both as reasons not to take it, because the combination can drop blood pressure to an unsafe level. Get emergency care for an erection lasting more than 4 hours, and stop the drug and seek prompt care for sudden loss of vision or hearing. ## How do tadalafil side effects compare with sildenafil? The two drugs share the same core side effects, but the mix differs: tadalafil is more associated with back pain and muscle aches, sildenafil with flushing and changes in color vision. Comparing the two labels' as-needed ED trials (for sildenafil, the flexible-dose trials, which reflect how it is prescribed): | Side effect | Tadalafil, as needed | Sildenafil, as needed (placebo) | | ------------------------ | -------------------- | ------------------------------- | | Headache | 11% to 15% | 16% (4%) | | Flushing | 2% to 3% | 10% (1%) | | Indigestion | 4% to 10% | 7% (2%) | | Back pain | 3% to 6% | 2% (2%) | | Muscle aches | 1% to 4% | Not in that table | | Abnormal vision | Not in that table | 3% (0%) | | Stopped for side effects | 3.1% (placebo 1.4%) | 2.5% (placebo 2.3%) | Sources: [Cialis](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895) Table 1 and [Viagra](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0b0be196-0c62-461c-94f4-9a35339b4501) Table 2 prescribing information, DailyMed. The Viagra label's sildenafil stopping rate comes from all its placebo-controlled studies, not only the flexible-dose ones. The Cialis label itself warns that rates from one drug's trials "cannot be directly compared" with another's, so read this as a rough guide. A network meta-analysis did put the drugs side by side: pooling 72 trials and more than 20,000 men for side effects, it found that at the usual starting doses compared, tadalafil had the lowest overall rate of side effects, while sildenafil had the highest rate but also the greatest effect on erections ([Chen et al., Eur Urol 2015](https://pubmed.ncbi.nlm.nih.gov/25817916/)). Which trade-off fits a given man is a conversation for his prescriber. Our [sildenafil side effects](/sildenafil-side-effects/) page has that drug's full numbers, and [tadalafil vs sildenafil](/tadalafil-vs-sildenafil/) compares onset, duration and cost. ## When should you talk to a clinician about side effects? Talk to the prescriber if a side effect is severe, does not go away, or makes you want to stop, and before taking tadalafil at all if you have heart disease, take any blood pressure medicine or alpha-blocker, or have kidney or liver problems. The label says men for whom sexual activity is inadvisable because of their heart should not use it, and that it was not studied in, and is not recommended for, men with a recent heart attack or stroke, unstable angina, or uncontrolled blood pressure or heart rhythm ([Cialis prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895)). You can also report a side effect to the FDA's MedWatch program, as MedlinePlus notes ([MedlinePlus: Tadalafil](https://medlineplus.gov/druginfo/meds/a604008.html)). Our guide on [when to see a doctor about ED](/when-to-see-a-doctor-about-ed/) covers what a proper check-up looks for. ## Sources 1. [Cialis (tadalafil) prescribing information, Eli Lilly and Company, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bcd8f8ab-81a2-4891-83db-24a0b0e25895) 2. [Viagra (sildenafil citrate) prescribing information, Pfizer, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0b0be196-0c62-461c-94f4-9a35339b4501) 3. [MedlinePlus: Tadalafil. U.S. National Library of Medicine](https://medlineplus.gov/druginfo/meds/a604008.html) 4. [Seftel AD, et al. A three-part study to investigate the incidence and potential etiologies of tadalafil-associated back pain or myalgia. Int J Impot Res. 2005](https://pubmed.ncbi.nlm.nih.gov/16034469/) 5. [Chen L, et al. Phosphodiesterase 5 inhibitors for the treatment of erectile dysfunction: a trade-off network meta-analysis. Eur Urol. 2015](https://pubmed.ncbi.nlm.nih.gov/25817916/) 6. [Campbell UB, et al. Acute nonarteritic anterior ischemic optic neuropathy and exposure to phosphodiesterase type 5 inhibitors. J Sex Med. 2015](https://pubmed.ncbi.nlm.nih.gov/25358826/) --- _Affiliate disclosure: some links on the web version of this site go to Bodybuilding Peptides (trybbpeptides.com), an affiliate destination, and we may earn a commission if you buy there. Our coverage is independent of that relationship. Details: https://theedreport.com/affiliate-disclosure/_