Tadalafil and Canagliflozin: Can They Be Taken Together?

Tadalafil and Canagliflozin: Understanding the Interaction

Published: 18 October 2026

Many men with type 2 diabetes wonder whether tadalafil and canagliflozin can be taken together safely. The good news is that no major direct interaction is commonly reported between tadalafil (a PDE5 inhibitor used for erectile dysfunction) and canagliflozin (an SGLT2 inhibitor used to manage blood sugar). However, both medicines can affect blood pressure, and your prescriber will carefully review your full medical history and current medications during an online consultation to ensure the combination is suitable for you.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine licensed in the UK to treat erectile dysfunction (ED). It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused [3][4]. Tadalafil does not cause an erection on its own—sexual stimulation is still needed.

Tadalafil is available in two forms: on-demand tablets (usually 10 mg or 20 mg, taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours) and daily low-dose tablets (2.5 mg or 5 mg, taken once a day regardless of when you plan to have sex) [4]. The branded version is known as Cialis, but generic tadalafil is widely available and works in exactly the same way.

At Cured Pharmacy, tadalafil is available from £7.95 after a consultation with a UK-registered prescriber. All PDE5 inhibitors, including tadalafil, require a clinical assessment to ensure they are safe and suitable for you.

What Is Canagliflozin and Why Is It Prescribed?

Canagliflozin is a prescription medicine used to manage type 2 diabetes. It belongs to a class of drugs called SGLT2 inhibitors, which work by helping your kidneys remove excess glucose (sugar) from your bloodstream through your urine [12]. By lowering blood sugar levels, canagliflozin helps reduce the risk of complications associated with diabetes, such as heart disease, kidney damage, and nerve problems.

Canagliflozin is usually taken once daily, with or without food. Common brand names include Invokana. Because it increases the amount of glucose in your urine, canagliflozin can slightly increase the risk of urinary and genital infections, so good hygiene is important. It can also cause a modest reduction in blood pressure, which is often beneficial for people with diabetes but must be considered when other medicines are added.

Erectile dysfunction is more common in men with diabetes than in the general population, partly because high blood sugar can damage blood vessels and nerves over time [1][2]. Many men taking canagliflozin for diabetes also seek treatment for ED, making it important to understand how these medicines work together.

Why Diabetes and ED Often Occur Together

Diabetes is a well-known risk factor for erectile dysfunction. Persistently high blood sugar levels can damage the small blood vessels and nerves that control erections [1][2]. Managing your diabetes well—through medication, diet, and lifestyle changes—can help reduce the risk of ED developing or worsening. If you have new or worsening erectile difficulties, it is important to see your GP, as ED can be an early warning sign of cardiovascular disease or poorly controlled diabetes.

Can You Take Tadalafil and Canagliflozin Together?

There is no major direct drug interaction commonly reported between tadalafil and canagliflozin [3][4][12]. This means that, in general, the two medicines do not interfere with each other's mechanism of action in a way that would make the combination unsafe. Many men with type 2 diabetes who are prescribed canagliflozin can also be prescribed tadalafil for erectile dysfunction, provided their overall health is suitable.

However, both medicines can lower blood pressure. Tadalafil causes blood vessels to relax (which is how it helps with erections), and canagliflozin can cause a modest drop in blood pressure as a secondary effect [3][4][12]. When taken together, there is a theoretical risk that blood pressure could fall more than expected, leading to dizziness, light-headedness, or fainting, especially when standing up quickly.

For this reason, your prescriber will carefully review your blood pressure, heart health, and any other medicines you take during your consultation. If you are already stable on canagliflozin and your blood pressure is well controlled, adding tadalafil is usually straightforward. Your prescriber may start you on a lower dose of tadalafil and monitor how you respond. It is essential to declare all your current medicines, including canagliflozin, during your online consultation so that your treatment can be tailored safely to you.

What Your Prescriber Checks Before Approving Tadalafil and Canagliflozin

When you request tadalafil through Cured Pharmacy's online consultation, a UK-registered prescriber will review your medical history and current medications to ensure the treatment is safe for you. If you are taking canagliflozin, the prescriber will check your blood pressure, cardiovascular health, and whether you have any conditions that make PDE5 inhibitors unsuitable (such as recent heart attack, unstable angina, severe heart failure, or very low blood pressure) [2][3][4].

The prescriber will also check for any medicines that must never be taken with tadalafil. These include nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, and recreational drugs known as 'poppers' (amyl or alkyl nitrites). Combining tadalafil with any of these can cause a dangerous drop in blood pressure and is absolutely contraindicated [3][4]. If you take any of these medicines, do not take tadalafil.

If you are also taking alpha-blockers (such as doxazosin or tamsulosin, often prescribed for prostate symptoms), the prescriber will ensure you are stable on the alpha-blocker and may start you on the lowest dose of tadalafil to minimise the risk of dizziness [3][4]. Similarly, if you take other blood-pressure-lowering medicines, the prescriber will assess whether the combination is manageable. Always be honest and thorough when listing your current medicines—this is the most important step in ensuring your safety.

Medicines That Affect Tadalafil Levels

Some medicines can increase or decrease the level of tadalafil in your bloodstream. Potent CYP3A4 inhibitors (such as ritonavir, cobicistat, ketoconazole, itraconazole, and clarithromycin) can raise tadalafil levels, requiring a reduced maximum dose [4][12]. Conversely, CYP3A4 inducers (such as rifampicin, carbamazepine, phenytoin, and St John's wort) can lower tadalafil levels and make it less effective [4]. Your prescriber will check for these interactions and adjust your dose or advise accordingly.

Practical Advice for Taking Tadalafil and Canagliflozin Safely

If your prescriber approves tadalafil while you are taking canagliflozin, follow these practical tips to use both medicines safely. Take each medicine exactly as prescribed: canagliflozin is usually once daily, and tadalafil is either on-demand (at least 30 minutes before sexual activity) or once daily at a low dose [4][12]. Do not take more tadalafil than prescribed, and never take it more than once in 24 hours.

Be aware of how you feel when you stand up, especially in the first few days of starting tadalafil. If you feel dizzy or light-headed, sit or lie down until the feeling passes, and mention it to your prescriber or pharmacist. Avoid heavy alcohol, as it can worsen erectile dysfunction, increase the risk of low blood pressure, and reduce the effectiveness of tadalafil [3][4]. Grapefruit juice can also raise tadalafil levels and should be avoided or limited.

Continue to manage your diabetes well: good blood sugar control, a healthy diet, regular physical activity, and maintaining a healthy weight can all improve erectile function over time [1][2]. If you develop any side effects from either medicine—such as persistent headache, indigestion, back pain (common with tadalafil), or genital itching or unusual discharge (which can occur with canagliflozin)—speak to your pharmacist or GP. Never stop a prescribed medicine without professional advice.

Warning Signs and When to Seek Urgent Help with Tadalafil and Canagliflozin

Most men tolerate tadalafil and canagliflozin well, but it is important to know the warning signs that require urgent medical attention. If you experience an erection lasting longer than four hours (priapism), go to A&E immediately—this is a medical emergency that can cause permanent damage if not treated promptly [3][4]. Priapism is rare but serious.

Seek urgent help if you have sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing, which may be accompanied by ringing in the ears or dizziness. These are rare but serious side effects of PDE5 inhibitors and require immediate medical assessment [3][4]. If you develop chest pain during or after sexual activity, stop and seek medical help—do not take nitrates (such as GTN spray) if you have used tadalafil in the past 48 hours, as the combination can be life-threatening.

With canagliflozin, be alert for signs of diabetic ketoacidosis (a serious complication that can occur even with near-normal blood sugar): symptoms include feeling very thirsty, needing to urinate more often, feeling sick, vomiting, stomach pain, confusion, unusual tiredness, or breath that smells fruity [12]. If you notice these symptoms, contact your GP or call 111 immediately. Also watch for signs of genital or urinary infection (pain, itching, unusual discharge) and see your GP if these occur.

Reporting Side Effects

If you experience any side effects from tadalafil or canagliflozin, you can report them via the Yellow Card Scheme at https://yellowcard.mhra.gov.uk or by searching for 'Yellow Card' in the Google Play or Apple App Store. Reporting side effects helps improve the safety of medicines for everyone. You can also discuss any concerns with your Cured Pharmacy pharmacist or your GP.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 18 October 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 18 October 2026]
3. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 18 October 2026]
4. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 18 October 2026]
5. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 18 October 2026]

Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.