Tadalafil and Sitagliptin: Can You Take Them Together?
Learn how these medicines work together and what your UK prescriber checks during your consultation.
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Tadalafil and Sitagliptin: Understanding the Interaction
Published: 25 October 2026
Many men wonder whether tadalafil and sitagliptin can be taken together safely. The good news is that no major interaction is commonly reported between tadalafil (a medicine for erectile dysfunction) and sitagliptin (a medicine for type 2 diabetes). However, because both conditions and their treatments can affect your overall health, your prescriber will carefully review your full medical history and current medicines during your consultation to ensure this combination is suitable for you.
Key takeaways
- No major interaction is commonly reported between tadalafil and sitagliptin
- Your prescriber reviews all your medicines to ensure tadalafil is safe for you
- Diabetes and ED often occur together; treating both is important for your health
- Never take tadalafil with nitrates, nicorandil, riociguat, or poppers
- Declare all medicines, including diabetes treatments, during your consultation
What Is Tadalafil and How Does It Work?
Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men [4]. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing more blood to flow in when you are sexually aroused. This can help you get and keep an erection suitable for sexual activity.
Tadalafil is available as the branded medicine Cialis and as generic tadalafil. It comes in two forms: on-demand tablets (10mg or 20mg) taken at least 30 minutes before sex, with effects lasting up to 36 hours, and daily tablets (2.5mg or 5mg) taken once a day [4]. All forms require sexual stimulation to work—tadalafil will not cause an erection on its own.
At Cured Pharmacy, tadalafil is available after an online consultation reviewed by a UK prescriber. Common side effects include headache, indigestion, back pain, and facial flushing, which are usually mild and temporary [4].
What Is Sitagliptin and Why Is It Prescribed?
Sitagliptin is a prescription medicine used to manage type 2 diabetes. It belongs to a class of medicines called DPP-4 inhibitors (also known as gliptins), which work by increasing the levels of natural substances called incretins. These help your body produce more insulin when your blood sugar is high and reduce the amount of sugar made by your liver.
Sitagliptin is often prescribed alongside diet and exercise to improve blood sugar control in adults with type 2 diabetes. It may be used on its own or in combination with other diabetes medicines such as metformin. The usual dose is 100mg once daily, though your doctor may adjust this if you have kidney problems.
Type 2 diabetes and erectile dysfunction often occur together. High blood sugar over time can damage blood vessels and nerves, including those needed for erections [1]. Managing your diabetes well with medicines like sitagliptin can be an important part of your overall health, including sexual health.
The Link Between Diabetes and Erectile Dysfunction
Men with diabetes are more likely to experience erectile dysfunction than men without diabetes [1]. This is because diabetes can damage the small blood vessels and nerves throughout the body, including those that supply the penis. Good diabetes control, regular exercise, maintaining a healthy weight, and not smoking can all help reduce this risk and improve erectile function.
At a glance
Can You Take Tadalafil and Sitagliptin Together?
No major interaction is commonly reported between tadalafil and sitagliptin. These two medicines work in different ways and on different systems in the body: tadalafil affects blood flow to the penis, while sitagliptin helps control blood sugar levels. There is no known mechanism by which sitagliptin would interfere with how tadalafil works, or vice versa.
However, it is essential that your prescriber knows about all the medicines you are taking, including sitagliptin and any other diabetes treatments. During your online consultation at Cured Pharmacy, you will be asked to list all your current medicines so the prescriber can check for any potential issues and ensure tadalafil is safe and suitable for you.
Some men with diabetes may also be taking other medicines—such as blood pressure tablets or cholesterol-lowering drugs—that can interact with tadalafil. Your prescriber will review your complete medication list and medical history to make sure the combination is appropriate. Never stop or change a prescribed medicine without speaking to your doctor or pharmacist first.
What Does Your Prescriber Check Before Approving Tadalafil?
Before prescribing tadalafil, your prescriber will review your full medical history and current medicines to ensure it is safe for you [2]. They will check whether you have any heart or blood vessel problems, as sexual activity itself can put strain on the heart. Tadalafil is not suitable if you have had a recent heart attack or stroke, have unstable angina, severe heart failure, or very low blood pressure.
Your prescriber will also check that you are not taking any medicines that must never be combined with tadalafil. These include nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites). Taking tadalafil with any of these can cause a dangerous drop in blood pressure [4]. Do not take tadalafil together with these medicines.
If you are taking an alpha-blocker for prostate symptoms or high blood pressure (such as doxazosin or tamsulosin), your prescriber will need to ensure you are stable on that medicine and may start you on a lower dose of tadalafil to reduce the risk of dizziness or fainting [4]. Similarly, certain medicines that affect how the liver processes tadalafil—such as some antibiotics, antifungals, or HIV medicines—may require dose adjustments.
Declaring All Your Medicines
It is vital to list every medicine you take during your consultation, including prescription medicines, over-the-counter treatments, herbal remedies, and supplements. This allows the prescriber to spot any potential interactions and choose the safest dose and treatment plan for you. If you start a new medicine after being prescribed tadalafil, let your doctor or pharmacist know you are taking an ED treatment.
Always Declare All Medicines
During your online consultation, list every medicine you take—including sitagliptin, other diabetes treatments, and over-the-counter products. This allows your prescriber to check for interactions and ensure tadalafil is safe and suitable for you.
Practical Advice for Taking Tadalafil with Sitagliptin
If your prescriber approves tadalafil and you are already taking sitagliptin, you can take both medicines as directed. There is no need to separate the doses or take them at different times of day, though you should follow the specific instructions for each medicine. For example, sitagliptin is usually taken once daily with or without food, while on-demand tadalafil is taken at least 30 minutes before sexual activity.
Continue to manage your diabetes as advised by your doctor. Good blood sugar control, regular physical activity, a balanced diet, and maintaining a healthy weight can all improve erectile function as well as your overall health [1]. Avoid heavy alcohol, as it can worsen erectile dysfunction and add to the blood-pressure-lowering effect of tadalafil, increasing the risk of dizziness.
If you experience any new or unusual symptoms after starting tadalafil—such as dizziness, chest pain during sex, or an erection lasting more than four hours—seek medical help immediately. These are rare but serious side effects that need urgent attention. If you have any questions or concerns about taking tadalafil and sitagliptin together, speak to your pharmacist or prescriber.
Other Diabetes Medicines and Tadalafil Interactions
Sitagliptin is just one of many medicines used to treat type 2 diabetes. Other common diabetes treatments include metformin, gliclazide, empagliflozin, and insulin. No major interactions are commonly reported between tadalafil and these standard diabetes medicines. However, your prescriber will still review your full medication list during your consultation to ensure everything is compatible.
Some men with diabetes also take medicines for related conditions, such as high blood pressure or high cholesterol. Blood pressure medicines can add to the blood-pressure-lowering effect of tadalafil, which may cause dizziness, especially when standing up. This is usually manageable, but your prescriber needs to know about all your medicines so they can choose the right dose and give you appropriate advice.
If you are taking any medicine not listed in this article, do not assume the combination with tadalafil is automatically safe. Always declare every medicine during your consultation. The prescriber and pharmacist are trained to check for interactions and will only approve tadalafil if it is safe and suitable for your individual circumstances. If you are unsure about any aspect of your treatment, ask your pharmacist or doctor for advice.
When to See Your GP
If you are experiencing erectile dysfunction for the first time, it is important to see your GP for a full assessment [1]. ED can be an early warning sign of underlying health problems such as heart disease, high blood pressure, or poorly controlled diabetes. Your GP can investigate the cause, optimise your diabetes treatment, and refer you for specialist advice if needed. Treating ED is important, but so is addressing any underlying health issues.
When to get urgent help
- Erection lasting more than 4 hours (priapism)—go to A&E immediately
- Sudden loss of vision or hearing—stop tadalafil and seek urgent medical help
- Chest pain during sex—stop activity, do not take more tadalafil, call 999 if pain does not resolve
- Severe dizziness or fainting after taking tadalafil—seek same-day medical advice
- Allergic reaction (rash, swelling of face or throat, difficulty breathing)—call 999
Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.
Scientific References
- NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 25 October 2026]
- National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 25 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 25 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.
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Your Questions Answered
Can't find your answer? Our UK pharmacists review every consultation and can help.
Is it safe to take tadalafil if I have type 2 diabetes?
Yes, tadalafil can be prescribed for men with type 2 diabetes, provided your prescriber confirms it is safe based on your full medical history and current medicines. Diabetes and ED often occur together, and treating ED is an important part of overall health.
Will sitagliptin affect how well tadalafil works?
No, sitagliptin does not interfere with how tadalafil works. These medicines act on different systems in the body, and no major interaction is commonly reported between them.
Do I need to take tadalafil and sitagliptin at different times?
No, there is no need to separate the doses. You can take both medicines as directed by your prescriber—sitagliptin is usually once daily, while on-demand tadalafil is taken before sexual activity.
Can tadalafil help with erectile dysfunction caused by diabetes?
Tadalafil can help improve erectile function in men with diabetes by increasing blood flow to the penis when you are sexually aroused. However, good diabetes control and a healthy lifestyle are also important for managing ED.
What should I tell my prescriber during my tadalafil consultation?
List all your current medicines (including sitagliptin and any other diabetes treatments), any medical conditions (especially heart, liver, or kidney problems), and any allergies. This helps the prescriber ensure tadalafil is safe and suitable for you.
Are there any diabetes medicines that cannot be taken with tadalafil?
No major interactions are commonly reported between tadalafil and standard diabetes medicines. However, your prescriber will review your full medication list during your consultation to check for any potential issues.
Can I drink alcohol while taking tadalafil and sitagliptin?
Heavy alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect of tadalafil, increasing the risk of dizziness. It is best to limit alcohol and drink in moderation.
What should I do if I start a new medicine after being prescribed tadalafil?
Tell your doctor or pharmacist that you are taking tadalafil so they can check for any interactions with the new medicine. Never stop or change a prescribed medicine without professional advice.
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