Tadalafil (Cialis) Side Effects: Headache, Back Pain, Blood Pressure and Who Should Not Take It

Short answer: Tadalafil, the medicine in Cialis, is licensed in the UK for erection problems, and like all medicines it can cause side effects. Common side effects include headache, flushing, nasal congestion, dyspepsia (indigestion), back pain, myalgia (muscle aches) and pain in the arms and legs. In the UK product information (Cialis SmPC, section 4.8), each of these is common, affecting up to 1 in 10 men, none is listed as very common, and the side effects reported are described as transient and generally mild or moderate. Daily tadalafil, 2.5mg or 5mg, has the same list. Tadalafil can lower blood pressure a little (SmPC 4.4), and it must never be taken with nitrates in any form, including poppers. Tadalafil's product information says that at least 48 hours should pass after the last dose of tadalafil before a nitrate is considered, even in an emergency. Get help straight away for chest pain during or after sex, an erection lasting longer than 4 hours, or a sudden loss of sight or hearing. Less common side effects are listed in the leaflet in your pack. Please read it before your first dose.

This guide follows the UK product information for Cialis and generic tadalafil, the Cialis Together leaflet and the NHS, as of October 2026. A GPhC-registered pharmacist reviews every consultation before anything is supplied.

What are the side effects of tadalafil (Cialis)?

The common side effects of tadalafil (Cialis) are headache, flushing, a blocked or stuffy nose, indigestion, back pain, muscle aches and pain in the arms or legs, each affecting up to 1 in 10 men; none is very common. Here is every side effect in the table in section 4.8 of the UK product information, in plain words:

* Reported since the medicine came into use, not in the placebo-controlled trials. For stroke, mini-stroke, the heart problems, chest pain and sudden cardiac death, most of the men had existing risk factors for heart disease.

Source: Cialis 10 mg and 20 mg SmPC, section 4.8 (emc 7431, revised January 2026): placebo-controlled trials in 8,022 men on tadalafil and 4,422 on a dummy tablet, taken when needed or daily (including by men treated for prostate symptoms), and reports since. The product information for daily Cialis 5mg, a generic tadalafil (Teva) and Cialis Together gives the same list. It adds that diarrhoea was reported more often in men over 65, and dizziness and diarrhoea in men over 75. Less common side effects are listed in the leaflet in your pack. Please read it before your first dose.

Lists for different medicines cannot be compared to show that one causes fewer side effects. For sildenafil, see Viagra side effects; for how the tablets differ, sildenafil vs tadalafil.

Does tadalafil 20mg cause more side effects than 10mg or 5mg?

It can: headache, indigestion, back pain and muscle aches become more common as the dose goes up, although no separate rates are given for each strength (SmPC 4.8). The usual dose is 10mg when needed or 5mg daily, and the pharmacist decides yours: see tadalafil dosage.

Are the side effects of daily tadalafil different?

No: the UK product information gives one list for tadalafil taken daily or when needed, from trials of both (Cialis SmPC 4.8), so it cannot show that either causes fewer side effects. Our daily tadalafil page says: Common side effects include flushing, nasal congestion, dyspepsia (indigestion), headache, back pain, myalgia (muscle aches) and pain in the arms and legs.

The product information notes two things about daily use: most headaches happen within 10 to 30 days of starting, and slightly more men than on a dummy tablet had changes on a heart tracing (ECG), mainly a slow heart rate (sinus bradycardia); most of these changes were not linked to any side effect (SmPC 4.8).

Why does tadalafil cause back pain and muscle aches?

The UK product information does not say why: it lists back pain, muscle aches (myalgia) and pain in the arms and legs as common, up to 1 in 10 men, and says back pain and muscle aches become more common at higher doses (Cialis SmPC 4.8). It does not say when they start or how long they last, and describes the side effects reported as transient and generally mild or moderate.

Which side effects need urgent help?

Get help straight away for chest pain, dizziness or fainting during or after sex, an erection lasting longer than 4 hours, or a sudden change in or loss of your sight or hearing. Every Solira erectile dysfunction consultation gives these warnings:

• Cardiovascular symptoms. Stop and call 999 if you get chest pain, dizziness or fainting during or after sexual activity. Do not take another dose.
• Prolonged erection. Seek emergency treatment for an erection lasting longer than 4 hours. This is a medical emergency.
• Vision changes. Stop treatment and contact a doctor if you notice any sudden change or loss of vision.
• Sudden hearing loss. Stop the medication and seek urgent medical attention if your hearing suddenly drops or is lost in either ear.

Why, from the UK product information: an untreated erection lasting 4 hours or more can damage the penis and cause a permanent loss of erections (SmPC 4.4). NAION, a sudden loss of blood supply to the optic nerve, has been reported with tadalafil and similar medicines, and observational data suggest a higher risk after taking them; anyone who has lost the sight of one eye from it must not take tadalafil (SmPC 4.3 and 4.4). Sudden hearing loss has been reported too (SmPC 4.4). Get urgent help, also, for a serious allergic reaction, such as a swollen throat or tongue or difficulty breathing (NHS). For urgent medical concerns, call NHS 111 or 999.

Never take tadalafil with nitrates in any form, including nicorandil or amyl nitrite (poppers): together they can lower your blood pressure too far. In an emergency, tell the doctor or paramedic that you take tadalafil and when you last took it. Tadalafil's product information says that at least 48 hours should pass after the last dose of tadalafil before a nitrate is considered, even in an emergency. This is why the time matters:

Does tadalafil lower blood pressure?

Yes, a little: tadalafil widens blood vessels, causing mild and short-lived falls in blood pressure (Cialis SmPC 4.4). In healthy volunteers it made no significant difference compared with a dummy tablet: the average largest fall was 1.6 mmHg in the top (systolic) number and 0.8 mmHg in the bottom (diastolic) number lying down, and 0.2 and 4.6 mmHg standing (SmPC 5.1).

Low blood pressure is an uncommon side effect, up to 1 in 100 men, reported more often in men already on blood pressure medicines, and high blood pressure is uncommon too (SmPC 4.8).

Drinking less alcohol can help your erections. With tadalafil or avanafil, alcohol can also make low blood pressure more likely, which can make you feel dizzy or light-headed. More in Viagra, Cialis and alcohol.

The product information rules tadalafil out with uncontrolled high blood pressure or a reading below 90/50 (SmPC 4.3). In our consultation:

• Very low blood pressure, below 90/50: we do not supply tadalafil.
• We ask for a reading from the last 12 months, and one above 170/100, or none, is flagged for the pharmacist.

Can you take tadalafil with blood pressure medication?

Often yes, with checks: in studies, tadalafil had no clinically significant interaction with the main types of blood pressure medicine (amlodipine, enalapril, metoprolol, a thiazide and angiotensin II receptor blockers), and side effects in the main trials were no different in men taking them, although with these medicines it may lower blood pressure a little further, in general by a minor amount (Cialis SmPC 4.5). Alpha-blockers need care: doxazosin with tadalafil lowered blood pressure significantly more for at least 12 hours, which can cause symptoms, including fainting, so the combination is not recommended, and caution is advised with any alpha-blocker, such as tamsulosin or alfuzosin (SmPC 4.4 and 4.5). When daily tadalafil is started, a possible change to the dose of your blood pressure medicine should be considered (Cialis 5mg SmPC 4.4). If you feel dizzy or sick, see your GP to review your blood pressure medicine.

In our consultation, blood pressure medicines are a caution the pharmacist reviews, not a stop. We do not supply tadalafil in either form with doxazosin, or tadalafil taken when needed with any other alpha-blocker; daily tadalafil may be offered at 2.5mg if you expect to have sex at least twice a week and your alpha-blocker dose has stayed the same recently, without dizziness or fainting.

Is it safe to take tadalafil every day?

Yes, as the daily tablet: tadalafil is licensed in the UK as a once-a-day tablet, usually 5mg, which may be lowered to 2.5mg depending on how well you tolerate it, and its product information gives the same list of side effects as for tadalafil taken when needed (Cialis SmPC 4.2 and 4.8). It is for men who expect to have sex at least twice a week. The available data does not suggest that taking it every day works better than taking tadalafil when needed. The 10mg and 20mg tablets are not recommended for continuous daily use (SmPC 4.2).

• Not offered if: you have any liver or kidney disease, or you take doxazosin.
• How much we supply: 28 tablets on a first supply, up to 56 on later supplies.
• GP notification. Daily tadalafil should be added to your regular medication record. We will contact your GP with your consent, or you can tell them yourself. Will you tell my GP?

Does tadalafil have long-term side effects?

The UK product information does not list separate side effects for long-term use, and says continued daily use should be reassessed from time to time (SmPC 4.2). In three studies of daily 10mg or 20mg over 6 or 9 months, two found falls in sperm count and concentration that it calls of unlikely clinical relevance; it says clinical studies suggest an effect on fertility is unlikely, although some men had a lower sperm concentration (SmPC 4.6 and 5.1). If you keep using tadalafil, a review is needed every 6 to 12 months.

Can tadalafil cause headaches or palpitations?

Yes: headache is a common side effect, up to 1 in 10 men, and palpitations and a fast heartbeat are uncommon, up to 1 in 100 (Cialis SmPC 4.8). Headache becomes more common at higher doses, and migraine is rare. If headaches bother you or do not go away, tell us: the NHS says a pharmacist may be able to advise how to reduce a side effect. The NHS lists noticeable heartbeats (palpitations) among the possible serious side effects, and says to call NHS 111 if you think you are having a serious side effect.

Cardiovascular symptoms. Stop and call 999 if you get chest pain, dizziness or fainting during or after sexual activity. Do not take another dose.

Does tadalafil affect testosterone or cause hair loss?

Neither is listed: the UK product information for Cialis does not list hair loss or mention testosterone (SmPC 4.8 and 5.1), nor does the NHS page on tadalafil. If you are worried about your testosterone, your GP can check it. If this is your first time with erection problems, see your GP to check your blood sugar, cholesterol and testosterone, and have a heart health check at least every 5 years. If you take finasteride for hair loss, tell us: the product information advises caution with medicines of that kind (SmPC 4.5), and our consultation flags it for the pharmacist. For hair loss itself, see our hair loss treatments.

Is tadalafil safe, and who should not take it?

For most men, yes: tadalafil is licensed in the UK for erectile dysfunction in adult men, and the NHS says most adults can take it, but it is not suitable for everyone. Not suitable if you take:

• Nitrates in any form, including nicorandil or amyl nitrite (poppers)
• Riociguat (Adempas) or vericiguat (Verquvo)
• An HIV protease inhibitor (atazanavir, darunavir, ritonavir, fosamprenavir, lopinavir, saquinavir or tipranavir)
• Ketoconazole, itraconazole, voriconazole or clarithromycin
• Or have severe cardiovascular disease

Our consultation also does not supply it if any of these apply, among other reasons:

• Currently taking another PDE5 inhibitor (sildenafil, tadalafil, vardenafil or avanafil, including for lung blood pressure or prostate symptoms) or any other erectile dysfunction treatment
• Stroke or heart attack in the last 6 months
• Unstable angina, or angina during intercourse
• A heart condition for which a doctor has told you to avoid sex or strenuous activity
• Heart failure that limits your everyday activity in the last 6 months
• Uncontrolled heart rhythm problem (arrhythmia)
• Severe liver impairment
• Severe kidney failure, eGFR under 30, or dialysis
• Loss of sight in one eye from NAION (a sudden loss of blood supply to the optic nerve), whether or not it happened while taking an erectile dysfunction medicine
• Very low blood pressure, below 90/50

Nor do we supply tadalafil if you have ever had an allergy or reaction to it, and its product information rules it out for anyone allergic to tadalafil or the tablet's other ingredients (SmPC 4.3). It advises caution with a curved penis or Peyronie's disease, and with conditions that can make priapism more likely, such as sickle cell anaemia, multiple myeloma or leukaemia (SmPC 4.4): our consultation asks about these and flags them for the pharmacist.

With a liver problem, tadalafil taken when needed is supplied at 10mg at most. We supply tadalafil for erectile dysfunction only. If you have urinary symptoms, please see your GP. A GPhC-registered pharmacist reviews your answers before anything is sent, and if they cannot approve your order, we refund you in full.

Is tadalafil bad for your heart?

Not for most men, but sex puts some strain on the heart, so heart health is considered before treatment, and tadalafil must not be used by men with heart disease for whom sex is inadvisable (SmPC 4.3 and 4.4). Heart attack, sudden cardiac death, unstable angina, abnormal heart rhythms and stroke have been reported, mostly in men with existing risk factors for heart disease, and the product information says it is not possible to say for certain whether they were related to those risk factors, to tadalafil, to sex, or to a mix of these or other factors (SmPC 4.4). Heart attack is rare, up to 1 in 1,000 men (SmPC 4.8). We ask which risk factors for heart disease apply to you, including these; with three or more, we cannot supply treatment until your GP has assessed your heart health:

• Uncontrolled high blood pressure
• High cholesterol
• Diabetes
• Smoking
• Obesity
• Physical inactivity
• Family history of cardiovascular disease

Chest pain, breathlessness, palpitations or faintness with everyday activity need to be checked by a doctor before erectile dysfunction treatment can be considered.

What are the side effects of Cialis Together?

Common side effects include headache, back pain, muscle aches, pain in the arms and legs, flushing, a blocked nose and indigestion. These are normally mild to moderate. Less common side effects are listed in the leaflet in your pack. Please read it before your first dose.

Cialis Together contains tadalafil 10mg, the same active ingredient as prescription Cialis. It is a pharmacy medicine: we supply Cialis Together after a pharmacist consultation, with no prescription needed, to men aged 18 to 64. If you would use it at least twice a week: Cialis Together is not for frequent use. Please see your GP, or start our full consultation to ask about a daily treatment. Erection problems can be an early sign of heart disease, diabetes or high blood pressure. Please book a check-up with your GP as soon as you can, within 6 months of starting Cialis Together.

How can you avoid or reduce tadalafil side effects?

You cannot rule them out, but you can lower the chance:

• Keep to the limit. Taken when needed: Take one tablet no more than twice a week, and never more than once in 24 hours. Taken daily: Take one tablet a day, at about the same time each day.
• Tell us every medicine you take. Some raise the amount of tadalafil in your blood and can make side effects more likely (SmPC 4.5); with erythromycin, aprepitant, diltiazem, fluconazole or verapamil, we supply it at 10mg taken when needed or 2.5mg daily.
• Grapefruit juice. Tadalafil: avoid grapefruit juice. It can raise tadalafil levels too (SmPC 4.5).
• Alcohol. Drinking less alcohol can help your erections.

When you reorder, we ask how your last tablets worked and about side effects, and you can choose the same dose or, where there is one, a lower strength; the pharmacist checks your answers before anything is sent. For timing, see how long tadalafil lasts, or see all our erectile dysfunction treatments.