Tadalafil and Insulin: Can They Be Taken Together?

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Key takeaways

• Tadalafil and insulin do not directly interact and can usually be taken together safely
• Your prescriber will check your diabetes control, heart health, and all other medicines before prescribing
• Never take tadalafil with nitrates, nicorandil, or riociguat—this combination is dangerous
• Good diabetes control and a healthy lifestyle improve erectile function and tadalafil effectiveness
• Declare all medicines, including insulin and diabetes tablets, during your online 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 phosphodiesterase type 5 (PDE5) inhibitors, which work by relaxing the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused. Tadalafil does not cause an erection on its own—sexual stimulation is still needed for it to work [4].

Tadalafil is available in two forms: on-demand tablets (usually 10 mg or 20 mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) and daily low-dose tablets (2.5 mg or 5 mg taken once a day) [4]. The long duration of action is why tadalafil is sometimes called the 'weekend pill'. It does not affect your blood sugar levels directly and works only on the blood vessels in the penis and lungs.

Common brand names include Cialis (the original branded version) and various generics. At Cured Pharmacy, tadalafil is available on prescription after an online consultation with a UK-registered prescriber, who will check that it is safe and suitable for you.

What Is Insulin and Why Do People Take It?

Insulin is a hormone that helps control blood sugar (glucose) levels in the body. People with type 1 diabetes do not produce insulin naturally, so they must inject it every day to stay healthy. Some people with type 2 diabetes also need insulin when other treatments (such as tablets or lifestyle changes) are not enough to keep their blood sugar within a safe range.

There are many types of insulin, including rapid-acting, short-acting, intermediate-acting, and long-acting formulations. Your diabetes team will prescribe the type and dose that suits your individual needs. Insulin is usually injected under the skin using a pen device or syringe, and the timing and dose depend on your blood sugar readings, meals, and activity levels.

Diabetes—especially when blood sugar is not well controlled over time—can damage blood vessels and nerves throughout the body, including those needed for erections [1]. This is why erectile dysfunction is more common in men with diabetes. Managing your diabetes well, including taking insulin as prescribed, is an important part of protecting your sexual health as well as your overall health.

At a glance

Do Tadalafil and Insulin Interact with Each Other?

Tadalafil and insulin do not have a direct drug interaction [4]. Tadalafil works on an enzyme (PDE5) in the blood vessels of the penis, while insulin works on glucose receptors throughout the body to lower blood sugar. They act on completely different systems, so taking tadalafil will not change how your insulin works, and insulin will not change how tadalafil works.

However, it is important to understand that having diabetes—and especially poorly controlled diabetes—can itself cause or worsen erectile dysfunction [1]. High blood sugar over time damages the small blood vessels and nerves that are essential for getting and keeping an erection. This means that even though the two medicines do not interact, your overall diabetes control and any complications from diabetes (such as heart disease, high blood pressure, or nerve damage) will affect whether tadalafil is safe and effective for you.

Your prescriber will ask about your diabetes during the consultation: how long you have had it, what your recent HbA1c (average blood sugar) levels are, whether you have any complications such as heart disease or kidney problems, and what other medicines you take. This full picture helps them decide whether tadalafil is suitable and what dose to recommend.

Why Your Prescriber Needs to Know About Your Diabetes

Even though tadalafil and insulin can be taken together, diabetes increases your risk of cardiovascular (heart and blood vessel) problems, which are the main safety concern when prescribing any PDE5 inhibitor [2]. Your prescriber will check whether you have any history of heart attack, stroke, angina, heart failure, or very low blood pressure, as these conditions may mean tadalafil is not safe for you. They will also ask about other diabetes medicines you take, because some (such as certain blood pressure tablets) can interact with tadalafil or add to its blood-pressure-lowering effect.

What Your Prescriber Will Check Before Prescribing Tadalafil

When you request tadalafil through Cured Pharmacy's online consultation, a UK-registered prescriber will review your answers carefully. They will ask about your general health, your diabetes (type, duration, control, complications), all current medicines (including insulin, other diabetes tablets, blood pressure medicines, and any over-the-counter or herbal products), and your cardiovascular history [2].

You must tell your prescriber if you take any nitrate medicines (such as GTN spray, isosorbide mononitrate, or glyceryl trinitrate tablets for angina), nicorandil, or riociguat, because these must never be taken with tadalafil—the combination can cause a dangerous drop in blood pressure [4]. You should also mention alpha-blockers (such as doxazosin or tamsulosin, often used for prostate symptoms), as these can interact with tadalafil and cause dizziness or fainting; if you take an alpha-blocker, your prescriber will usually start you on the lowest dose of tadalafil and make sure you are stable on the alpha-blocker first [4].

The prescriber will also check whether sexual activity is safe for you. If you have had a recent heart attack or stroke, unstable angina, severe heart failure, or very low blood pressure, tadalafil may not be suitable [2][4]. If you have any eye problems (especially a history of sudden vision loss called NAION) or severe kidney or liver disease, the prescriber will take this into account when deciding on the dose or whether to prescribe at all.

Practical Advice for Taking Tadalafil and Insulin Safely

If your prescriber approves tadalafil, continue taking your insulin exactly as prescribed by your diabetes team—do not stop or change your insulin dose without their advice. Tadalafil will not affect your blood sugar directly, but it is still important to monitor your levels regularly, especially if you are adjusting your diabetes treatment or if you are unwell.

Take tadalafil as directed: on-demand tablets (10 mg or 20 mg) should be taken at least 30 minutes before sexual activity, and the effect can last up to 36 hours; daily tablets (2.5 mg or 5 mg) are taken once a day at the same time, regardless of when you plan to have sex [4]. Tadalafil can be taken with or without food, but heavy meals or excessive alcohol can reduce its effectiveness and increase the risk of side effects such as dizziness or headache.

Be aware of side effects: common ones include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. These are usually mild and go away on their own. However, seek urgent medical help (call 999 or go to A&E) if you experience an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or chest pain during sex. If you feel dizzy or faint after taking tadalafil, sit or lie down and avoid driving or operating machinery until you feel better.

Lifestyle Tips to Improve Erectile Dysfunction

Managing your diabetes well is one of the most important things you can do to improve erectile dysfunction [1]. Aim to keep your blood sugar levels within your target range, attend your diabetes check-ups, and follow your healthcare team's advice on diet, exercise, and medicines. Losing weight (if you are overweight), stopping smoking, cutting down on alcohol, and staying physically active can all help improve blood flow and erectile function [2]. Tadalafil works best when combined with a healthy lifestyle and good diabetes control.

Other Diabetes Medicines and Tadalafil Interactions

Many people with diabetes take other medicines alongside insulin, such as metformin, gliclazide, empagliflozin, or other tablets to control blood sugar. These diabetes medicines do not have any known direct interaction with tadalafil and can usually be taken together safely. However, you must declare all your current medicines during the online consultation so that your prescriber can check for any potential issues.

Some people with diabetes also take medicines for high blood pressure (such as amlodipine, ramipril, or losartan) or high cholesterol (such as atorvastatin or simvastatin). Blood pressure medicines can add to the blood-pressure-lowering effect of tadalafil, which may cause dizziness or light-headedness, especially when you stand up quickly [4]. This does not mean you cannot take them together, but your prescriber will review your blood pressure readings and may start you on a lower dose of tadalafil. Statins (cholesterol medicines) do not interact with tadalafil.

If you take any medicine not listed here, do not assume it is safe to combine with tadalafil. Always list every medicine, supplement, and herbal product you use in your consultation. Your prescriber and pharmacist will check each one individually to ensure there are no interactions or safety concerns.

What About Other ED Medicines?

If tadalafil is not suitable for you, or if you prefer a different option, other PDE5 inhibitors are available, including sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra) [3][5][6]. All of these work in a similar way and have the same safety considerations regarding insulin and diabetes medicines. Never take more than one PDE5 inhibitor at the same time, as this increases the risk of serious side effects. Your prescriber will help you choose the most appropriate treatment based on your individual circumstances.

When to get urgent help

• Erection lasting more than 4 hours (priapism)—call 999 or go to A&E immediately
• Sudden loss of vision or hearing—seek urgent medical help
• Chest pain during or after sex—stop activity, call 999, do not take nitrates if you have used tadalafil recently
• Severe dizziness, fainting, or very low blood pressure—seek same-day medical advice
• Allergic reaction (swelling of face, lips, tongue, or throat, difficulty breathing)—call 999

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.

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