Tadalafil and Cannabis: Is It Safe to Use Together?

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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 the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused [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 to allow spontaneity [4]. The branded version is called Cialis, but generic tadalafil is equally effective and more affordable.

Because tadalafil relaxes blood vessels throughout the body, it can cause a small drop in blood pressure. This is usually well tolerated, but it becomes important when combined with other substances that also lower blood pressure, including cannabis [4].

What is cannabis and how does it affect blood pressure?

Cannabis (also known as marijuana or weed) is a plant-based substance that contains active compounds called cannabinoids, the most well-known being THC (tetrahydrocannabinol) and CBD (cannabidiol). Cannabis is used recreationally and, in some countries, medicinally, though it remains a controlled substance under UK law.

Cannabis affects the cardiovascular system in complex ways. Shortly after use, it can cause a temporary increase in heart rate and, in some people, a rise in blood pressure. However, with continued use or in certain individuals, cannabis can cause blood pressure to drop, particularly when standing up (postural hypotension), leading to dizziness or fainting.

The blood-pressure effects of cannabis vary widely depending on the dose, method of use (smoking, vaping, edibles), individual tolerance, and other health factors. Because both cannabis and tadalafil can lower blood pressure, using them together may increase the risk of symptoms such as dizziness, light-headedness, or fainting, especially when moving from sitting to standing.

When to get urgent help

• Erection lasting more than four hours (priapism)—go to A&E immediately
• Sudden loss of vision or hearing—seek urgent medical help
• Severe chest pain during or after sex—call 999
• Severe dizziness, fainting, or rapid/irregular heartbeat—seek medical advice promptly
• Symptoms of severe allergic reaction (face/throat swelling, difficulty breathing)—call 999

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

Can you take tadalafil and cannabis together?

There is no absolute contraindication that forbids the use of tadalafil and cannabis together, unlike the strict prohibition against combining tadalafil with nitrates, nicorandil, riociguat, or poppers, which can cause a dangerous drop in blood pressure [4]. However, because both substances can lower blood pressure, their combined use does carry an increased risk of side effects.

The main concern is additive blood-pressure lowering. If you use cannabis and then take tadalafil (or vice versa), you may experience dizziness, light-headedness, fainting, or a rapid heartbeat. These effects are more likely if you are new to either substance, use a high dose of cannabis, consume alcohol at the same time, or have underlying cardiovascular conditions.

No major formal drug interaction between tadalafil and cannabis is listed in standard UK prescribing references, but the lack of a documented interaction does not mean the combination is risk-free. Your prescriber will ask about all substances you use, including recreational drugs, to assess whether tadalafil is safe for you and to advise on minimising risk [2][4].

What your prescriber will check

During your online consultation at Cured Pharmacy, the prescriber will ask about your use of cannabis and other recreational substances. They will also review your cardiovascular health, current medications, blood pressure, and any history of dizziness or fainting. If you use cannabis regularly or occasionally, it is essential to declare this honestly—prescribers are not there to judge, but to ensure your safety.

The prescriber may recommend starting on a lower dose of tadalafil, advising you to avoid using cannabis and tadalafil at the same time, or suggesting you monitor for symptoms such as dizziness. If you have underlying heart problems or take other blood-pressure-lowering medicines, extra caution is needed, and the prescriber may decide tadalafil is not suitable [2][4].

Practical advice: reducing risk when using tadalafil and cannabis

If your prescriber approves tadalafil and you choose to use cannabis, there are practical steps you can take to reduce the risk of side effects. First, avoid using both substances at the same time or in quick succession. For example, if you plan to take tadalafil before sexual activity, avoid using cannabis in the hours immediately before or after.

Start with the lowest effective dose of tadalafil, especially if you are new to the medicine or use cannabis regularly. Stay well hydrated, avoid heavy alcohol (which also lowers blood pressure and worsens ED), and be cautious when standing up quickly, as this is when dizziness is most likely to occur.

If you experience dizziness, sit or lie down until it passes. If you feel faint, have chest pain, a very rapid or irregular heartbeat, or any other concerning symptoms, stop using both substances and seek medical advice promptly. Always be honest with your prescriber about your cannabis use—this information is confidential and essential for your safety [1][2].

At a glance

Other medicines and substances that interact with tadalafil

Tadalafil has several important interactions beyond cannabis. Do not take tadalafil with nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or amyl/alkyl nitrites (poppers). These combinations can cause a severe and potentially life-threatening drop in blood pressure [4].

Alpha-blockers (such as tamsulosin, doxazosin, or alfuzosin, often prescribed for prostate problems) can also lower blood pressure. If you take an alpha-blocker, you must be stable on it before starting tadalafil, and your prescriber will usually recommend the lowest dose of tadalafil [4].

Potent CYP3A4 inhibitors—medicines such as ritonavir, cobicistat (found in some HIV treatments), Paxlovid, ketoconazole, itraconazole, or clarithromycin—can raise tadalafil levels in the blood, increasing the risk of side effects. Your prescriber will adjust the tadalafil dose or advise against use if you take these medicines [4]. Grapefruit juice can have a similar effect and should be avoided. Always declare every medicine, supplement, and recreational substance during your consultation.

Alcohol and tadalafil

Alcohol is another substance that lowers blood pressure and can worsen erectile dysfunction. Drinking heavily while taking tadalafil increases the risk of dizziness, headache, and fainting. Moderate alcohol (one or two units) is usually safe, but it is best to limit intake, especially if you are also using cannabis or other substances that affect blood pressure [1][4].

When to seek urgent help and long-term considerations

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, severe chest pain during sex, or symptoms of a severe allergic reaction such as swelling of the face or throat and difficulty breathing [4]. If you feel very dizzy, faint, or have a rapid or irregular heartbeat after using tadalafil and cannabis together, sit or lie down and seek medical advice promptly.

Erectile dysfunction can be an early warning sign of cardiovascular disease or diabetes, so it is important to see your GP for a full health check if you have new or worsening ED [1][2]. Your GP can assess your heart health, check your blood pressure and cholesterol, and discuss lifestyle changes such as stopping smoking, reducing alcohol, exercising regularly, and managing stress—all of which can improve both ED and overall health.

If you use cannabis regularly and find it is affecting your erections, heart rate, or blood pressure, consider discussing this with your GP or a specialist service. Cured Pharmacy's online consultation is designed to assess your suitability for tadalafil safely and conveniently, but it does not replace a full medical review by your GP, especially if you have complex health needs or use multiple substances [2].

How Cured Pharmacy can help

Cured Pharmacy is a GPhC-registered online pharmacy (GPhC 9012511) offering discreet, convenient access to tadalafil and other ED treatments after a confidential online consultation reviewed by a UK-registered prescriber. You can choose from a range of tadalafil products, including generic tadalafil from £7.95 (£6.36 with code Ednew on your first order), Tadalafil 20 mg (Teva) at £9.99 (£7.99 with code Ednew), Avarante 10 mg at £11.49 (£9.19 with code Ednew), and branded Cialis at £12.00 (£9.60 with code Ednew).

Your prescriber will review your medical history, current medicines, and any substance use to ensure tadalafil is safe and appropriate for you. If approved, your treatment is dispensed by our pharmacists and delivered discreetly to your door. If you have questions or concerns about using tadalafil alongside cannabis or any other substance, our team is here to provide clear, non-judgemental advice.

In summary

• Tadalafil and cannabis can both lower blood pressure, increasing the risk of dizziness or fainting when used together.
• There is no absolute contraindication, but you must declare cannabis use during your consultation for safety.
• Avoid using both substances at the same time and start with the lowest effective dose of tadalafil.
• Do not take tadalafil with nitrates, nicorandil, riociguat, or poppers—this combination is dangerous.
• Seek urgent help if you experience chest pain, severe dizziness, fainting, or an erection lasting over four hours.

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