Tadalafil and Blood Test Results Explained

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Tadalafil and Blood Test Results: What You Need to Know

Published: 7 November 2026

Many men wonder whether tadalafil and blood test results are connected, particularly if they're having routine health checks or starting treatment for erectile dysfunction. Tadalafil itself does not typically interfere with standard blood test results, but your prescriber will often check certain blood tests before prescribing to ensure the medicine is safe for you. Understanding what tests may be needed and why can help you feel confident about your treatment.

What Is Tadalafil and How Does It Work?

Tadalafil is a prescription medicine used 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 is the active ingredient in branded Cialis and is also available as a generic medicine at lower cost.

Tadalafil is available in two forms: on-demand tablets (usually 10mg or 20mg) taken at least 30 minutes before sexual activity, with effects lasting up to 36 hours; and daily tablets (2.5mg or 5mg) taken once a day, which allow for more spontaneous sexual activity [4]. Both forms require sexual stimulation to work and do not cause an automatic erection.

Because tadalafil affects blood vessels and blood pressure, your prescriber needs to check your overall health before prescribing it. This is where blood tests can play an important role in making sure the treatment is safe and suitable for you.

Does Tadalafil Affect Blood Test Results?

Tadalafil does not generally interfere with the accuracy of standard blood tests. If you are taking tadalafil and have blood tests for routine health monitoring, cholesterol, liver function, kidney function, or blood sugar levels, the medicine is not expected to alter those results in a clinically significant way [4][12].

However, it is always good practice to tell the healthcare professional taking your blood sample, or the doctor who ordered the test, about all medicines you are taking, including tadalafil. This ensures they have a complete picture of your health and can interpret any results correctly.

In rare cases, if you experience side effects such as prolonged dizziness, chest pain, or visual disturbances while taking tadalafil, your doctor may order specific blood tests to investigate the cause. These tests are not because tadalafil changes blood test results, but to check for underlying conditions that may be contributing to your symptoms.

What About Tadalafil and Blood Test Results for Hormones?

Tadalafil does not affect testosterone levels or other hormone blood tests. If your prescriber suspects that low testosterone or other hormonal imbalances are contributing to your erectile dysfunction, they may arrange blood tests to measure these hormones separately. Treating any underlying hormonal problem may improve your response to tadalafil or, in some cases, reduce the need for it [2].

What Blood Tests Does Your Prescriber Check Before Tadalafil?

Before prescribing tadalafil, your doctor or online prescriber will want to understand your overall health. While not every patient will need blood tests, they are commonly recommended if you have symptoms or risk factors for conditions that can cause ED or make tadalafil unsuitable [2].

Common blood tests include fasting blood glucose or HbA1c (to check for diabetes), lipid profile (cholesterol and triglycerides, as high cholesterol can affect blood vessels), and sometimes testosterone levels if symptoms suggest low levels. Kidney and liver function tests may also be checked, because these organs process tadalafil, and dose adjustments may be needed if they are not working well [4].

Erectile dysfunction can be an early warning sign of heart disease or diabetes, so blood tests help identify these conditions early [1][2]. If tests reveal an underlying problem, treating it can improve your erections and your long-term health. Your prescriber will discuss any abnormal results with you and may refer you to your GP or a specialist for further care.

How Tadalafil and Blood Pressure Are Connected

Tadalafil can cause a small, temporary drop in blood pressure because it relaxes blood vessels [4]. For most men, this is not a problem and may even be beneficial if blood pressure is slightly raised. However, if you already take medicines that lower blood pressure, the combined effect can sometimes cause dizziness or light-headedness.

Your prescriber will ask about all your current medicines during the consultation. If you take medicines for high blood pressure, they will check that it is safe to add tadalafil and may start you on a lower dose. Blood pressure is not usually measured by a blood test, but your GP may check it with a cuff during a routine appointment.

You must never take tadalafil if you use nitrate medicines (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites). The combination can cause a dangerous, sudden drop in blood pressure [3][4]. Always declare these medicines during your consultation.

Alpha-Blockers and Tadalafil

If you take an alpha-blocker for an enlarged prostate (such as tamsulosin, doxazosin, alfuzosin, or terazosin), there is also a risk of low blood pressure when combined with tadalafil [4]. Your prescriber will check that you are stable on the alpha-blocker and will usually start you on the lowest dose of tadalafil. Do not adjust either medicine yourself; always follow your prescriber's advice.

Tadalafil and Blood Test Results: Other Medicines That Interact

Some medicines can raise the level of tadalafil in your blood by slowing down how your body breaks it down. These include potent CYP3A4 inhibitors such as ritonavir, cobicistat (used in some HIV medicines), Paxlovid (used for COVID-19), and antifungal medicines like ketoconazole and itraconazole [4][12]. If you take any of these, your prescriber will reduce the maximum dose of tadalafil or may choose a different ED treatment.

Other medicines, called CYP3A4 inducers (such as rifampicin, carbamazepine, phenytoin, and the herbal remedy St John's wort), can make tadalafil less effective by speeding up how quickly your body clears it [4]. Your prescriber will review all your medicines during the consultation to check for these interactions.

Grapefruit juice can also raise tadalafil levels, so it is best to avoid drinking large amounts of it while taking this medicine. Heavy alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect, so moderation is advised [1][4].

Practical Advice: Using Tadalafil Safely

Always complete an honest and accurate online consultation or speak openly with your GP about your health, current medicines, and any symptoms. This allows your prescriber to check for interactions and ensure tadalafil is safe for you. If you have new symptoms, such as chest pain, dizziness, or visual changes, contact your GP or pharmacist before taking another dose.

Keep a list of all your medicines, including over-the-counter products and herbal remedies, and update it whenever something changes. If another doctor prescribes a new medicine, tell them you take tadalafil so they can check for interactions. Do not stop or change any prescribed medicine without advice from your prescriber.

If you need blood tests for any reason while taking tadalafil, mention the medicine to the healthcare professional. Although tadalafil does not usually affect test results, it helps them interpret your results in the context of your full medical history. If you experience an erection lasting more than four hours, sudden loss of vision or hearing, or chest pain during sex, seek urgent medical help [4].

When to See Your GP

If you have new or worsening erectile dysfunction, see your GP for a full assessment. ED can be an early sign of heart disease, diabetes, or other health problems that need treatment [1][2]. Your GP can arrange blood tests, review your medicines, and refer you to a specialist if needed. Treating the underlying cause may improve your erections and your overall health.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 7 November 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 7 November 2026]
3. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 7 November 2026]
4. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 7 November 2026]
5. Electronic Medicines Compendium. (n.d.). Summaries of Product Characteristics and Patient Information Leaflets. https://www.medicines.org.uk/emc/ [accessed 7 November 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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