Sildenafil and Insulin: Can You Take Them Together?

Takes less than 2 minutes to complete 100% online

What is sildenafil and how does it work?

Sildenafil is a medicine used to treat erectile dysfunction (ED) in men. 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 [3]. Sildenafil does not cause an erection on its own—you still need sexual stimulation for it to work.

The most common dose is 50 mg, taken about one hour before sexual activity, though your prescriber may adjust this to 25 mg or 100 mg depending on how well it works and whether you experience side effects [3]. You should not take sildenafil more than once a day. The effect typically lasts for around four to six hours, though this varies between individuals.

Sildenafil is available as a generic medicine and also under the brand name Viagra. At Cured Pharmacy, sildenafil 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 diabetes either do not produce enough insulin (type 1 diabetes) or their body does not respond properly to it (type 2 diabetes). Insulin injections replace or supplement the body's natural insulin to keep blood sugar levels within a healthy range and prevent serious complications such as heart disease, nerve damage, kidney problems, and vision loss.

There are several types of insulin, including rapid-acting, short-acting, intermediate-acting, and long-acting formulations. Your diabetes specialist or GP will prescribe the type and dose that best suits your needs. Insulin is usually injected under the skin using a pen device or syringe, and the timing and frequency depend on the type of insulin and your individual treatment plan.

Good blood sugar control is essential for overall health and can also help reduce the risk or severity of erectile dysfunction, as high blood sugar over time can damage blood vessels and nerves that are important for erections [1].

When to get urgent help

• Erection lasting more than 4 hours (priapism)—go to A&E immediately
• Sudden loss of vision or hearing—seek urgent medical attention
• Chest pain during sexual activity—stop and call 999 if pain does not resolve quickly
• Severe dizziness, fainting, or signs of very low blood pressure—seek same-day medical advice
• New or worsening symptoms related to your heart or diabetes—contact your GP or diabetes team promptly

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

Do sildenafil and insulin interact with each other?

Sildenafil and insulin do not have a direct pharmacological interaction, meaning that taking them together does not usually cause one medicine to affect how the other works in your body. Sildenafil is broken down mainly by liver enzymes, while insulin works by binding to receptors on cells to help glucose enter them. These are separate pathways, so the two medicines do not interfere with each other's mechanisms [3].

However, it is important to understand that diabetes itself—and some of its complications—can affect whether sildenafil is safe or effective for you. Men with diabetes are more likely to have cardiovascular disease, high blood pressure, high cholesterol, and nerve or blood vessel damage, all of which can influence ED treatment [1][2]. Your prescriber will take a full medical history and check for any conditions that might make sildenafil unsuitable, such as severe heart disease, very low blood pressure, or recent stroke.

If your diabetes is well controlled and you do not have serious complications, sildenafil can often be used safely. Your prescriber may also check your HbA1c (a measure of long-term blood sugar control) and ask about any other medicines you take, as some diabetes medications or treatments for related conditions can interact with sildenafil.

What your prescriber will check

Before prescribing sildenafil, your clinician will ask about your diabetes control, any complications (such as neuropathy, retinopathy, or cardiovascular disease), and all the medicines you currently take. They will also check your blood pressure and ask about your heart health, as some heart conditions make sildenafil unsuitable [2]. If you take other medicines for high blood pressure, high cholesterol, or other diabetes-related conditions, your prescriber will review these to ensure there are no unsafe combinations.

Other diabetes medicines and sildenafil interactions

While insulin itself does not interact with sildenafil, some people with diabetes take additional medicines that may require extra caution. For example, if you take an alpha-blocker such as doxazosin or tamsulosin (sometimes prescribed for high blood pressure or prostate symptoms), there is a risk of low blood pressure or dizziness when combined with sildenafil [3]. In this case, you should be stable on the alpha-blocker before starting sildenafil, and your prescriber will usually recommend the lowest dose of sildenafil initially.

Other blood-pressure medicines, such as ACE inhibitors, angiotensin receptor blockers, or calcium channel blockers, can also add to the blood-pressure-lowering effect of sildenafil. This does not mean you cannot take them together, but your prescriber will assess your overall cardiovascular health and may adjust doses if needed [2].

It is essential to tell your prescriber about every medicine you take, including over-the-counter products and herbal supplements. For example, St John's wort (sometimes used for low mood) can reduce the effectiveness of sildenafil, while grapefruit juice can raise sildenafil levels in the blood [3]. Your prescriber will review all of these factors during your consultation to ensure safe and effective treatment.

At a glance

Practical advice for taking sildenafil if you have diabetes

If you have diabetes and are considering sildenafil for erectile dysfunction, the most important step is to keep your blood sugar levels as well controlled as possible. Good diabetes management can improve blood vessel and nerve health, which in turn may improve your response to ED treatment [1]. Work closely with your diabetes team to optimise your HbA1c, blood pressure, and cholesterol levels.

When taking sildenafil, follow your prescriber's instructions carefully. Take the tablet about one hour before sexual activity, and remember that sexual stimulation is needed for it to work [3]. Avoid heavy meals and excessive alcohol before taking sildenafil, as both can reduce its effectiveness and increase the risk of side effects such as dizziness or flushing. If you experience side effects such as headache, indigestion, or a blocked nose, these are usually mild and temporary.

Monitor your blood sugar levels as usual, and be aware that sexual activity itself can affect blood glucose. If you are prone to low blood sugar (hypoglycaemia), check your levels before and after sex, and keep a fast-acting carbohydrate snack nearby if needed. If you notice any unusual symptoms or if sildenafil does not work as expected, speak to your prescriber—they may adjust the dose or suggest an alternative PDE5 inhibitor such as tadalafil or vardenafil.

When to seek medical advice

Seek urgent medical help if you experience an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or chest pain during sexual activity [3]. These are rare but serious side effects that require immediate attention. If you develop new or worsening symptoms related to your diabetes or heart health, contact your GP or diabetes team promptly.

Alternatives to sildenafil for men with diabetes and insulin use

If sildenafil is not suitable or does not work well for you, there are several other treatment options for erectile dysfunction. Other PDE5 inhibitors include tadalafil (Cialis), which can be taken on-demand or as a low daily dose and has a longer duration of action (up to 36 hours); vardenafil (Levitra), which works similarly to sildenafil; and avanafil (Spedra), which has a faster onset of action [4][5][6]. Your prescriber can discuss which option may be best for your circumstances.

For men who cannot take PDE5 inhibitors, or for whom they are not effective, other treatments include alprostadil cream (Vitaros) or alprostadil injections (Caverject), which work by a different mechanism to increase blood flow to the penis [7]. There are also vacuum erection devices and, in some cases, surgical options. Your GP or a specialist can provide more information about these alternatives.

It is also worth addressing any underlying causes of ED. For men with diabetes, improving blood sugar control, losing weight if needed, stopping smoking, reducing alcohol intake, and increasing physical activity can all help improve erectile function [1][2]. Psychological factors such as stress, anxiety, or relationship difficulties can also contribute to ED, and talking therapies or counselling may be beneficial. At Cured Pharmacy, our prescribers take a holistic approach and can provide advice on lifestyle measures alongside medication.

Why see your GP about new erectile dysfunction

If you are experiencing erectile dysfunction for the first time, it is important to see your GP for a full assessment. ED can be an early warning sign of cardiovascular disease or poorly controlled diabetes, and identifying and treating these conditions can improve both your general health and your sexual function [1][2]. Your GP can also check for other causes of ED and refer you to a specialist if needed.

In summary

• Sildenafil and insulin do not interact directly and can usually be taken together safely.
• Your prescriber will check your diabetes control, complications, and all other medicines before prescribing sildenafil.
• Good blood sugar control can improve erectile function and your response to ED treatment.
• Never take sildenafil with nitrates or nicorandil, as this can cause a dangerous drop in blood pressure.
• Seek urgent help if you have an erection lasting over four hours or sudden vision or hearing loss.

Frequently Asked Questions