Can You Take Tadalafil and Liothyronine Together?
Learn about this combination, what your prescriber checks, and how to use both medicines safely.
Takes less than 2 minutes to complete 100% online
ED Treatments We Offer
Pricing Disclaimer: Prices on some pages may not be up to date — the live pricing table below and pricing shown during consultation are official current prices and take precedence over any other figures on the site.
Tadalafil and Liothyronine: Understanding the Interaction
Published: 22 October 2026
Many men taking liothyronine for thyroid conditions wonder whether tadalafil and liothyronine can be used together safely. The good news is that no major direct interaction between these two medicines is commonly reported, but your prescriber will still need to review your full medical history and current medications. This page explains what each medicine does, what checks are needed, and the practical advice you should follow.
Key takeaways
- No major direct interaction is commonly reported between tadalafil and liothyronine.
- Your prescriber will check that your thyroid levels are stable before approving tadalafil.
- Continue taking liothyronine as prescribed; do not stop or change the dose without medical advice.
- Seek urgent help if you have chest pain, an erection lasting over four hours, or sudden vision or hearing loss.
- All ED prescriptions at Cured Pharmacy require an online consultation reviewed by a UK prescriber.
What Is Tadalafil and How Does It Work?
Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men [3][4]. It belongs to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors. When you are sexually aroused, your body releases a chemical that relaxes smooth muscle in the penis, allowing blood to flow in and produce an erection. Tadalafil helps by blocking an enzyme (PDE5) that would otherwise break down this chemical, making it easier to get and keep an erection when you are sexually stimulated [4].
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 [4]. Unlike some other ED treatments, tadalafil does not cause an automatic erection—sexual stimulation is still needed. It is the generic version of Cialis and is available at Cured Pharmacy following an online consultation with a UK prescriber.
What Is Liothyronine and Why Is It Prescribed?
Liothyronine is a synthetic form of triiodothyronine (T3), one of the thyroid hormones your body naturally produces. It is prescribed to treat an underactive thyroid gland (hypothyroidism), usually when levothyroxine (T4) alone is not fully effective or when a faster-acting thyroid hormone is needed. Thyroid hormones play a vital role in regulating your metabolism, energy levels, heart rate, and many other bodily functions.
An underactive thyroid can cause symptoms such as tiredness, weight gain, low mood, and reduced libido—some of which can contribute to erectile dysfunction [1][2]. By restoring normal thyroid hormone levels, liothyronine can improve overall wellbeing and may indirectly help with sexual function. However, it is important that thyroid hormone levels are carefully monitored by your doctor, as too much can cause heart palpitations, anxiety, and other side effects.
The Link Between Thyroid Health and Erectile Function
Research shows that thyroid disorders, particularly hypothyroidism, are associated with a higher risk of erectile dysfunction [2]. Low thyroid hormone levels can reduce sex drive, cause fatigue, and affect blood flow—all of which can make it harder to achieve or maintain an erection. Treating the underlying thyroid condition with medicines like liothyronine often improves energy and libido, but some men may still benefit from additional ED treatment such as tadalafil.
At a glance
Do Tadalafil and Liothyronine Interact With Each Other?
There is no well-documented direct pharmacological interaction between tadalafil and liothyronine. These medicines work through different mechanisms in the body: tadalafil acts on blood vessels in the penis, while liothyronine replaces a thyroid hormone that regulates metabolism. Neither medicine is known to significantly affect the breakdown or effectiveness of the other.
However, this does not mean the combination is automatically safe for everyone. Both medicines can affect your cardiovascular system. Tadalafil can lower blood pressure slightly, and thyroid hormones influence heart rate and rhythm [4]. If your thyroid levels are not well controlled—either too high or too low—this can put extra strain on your heart and blood vessels. That is why your prescriber will check your thyroid function, heart health, and any other medicines you take before approving tadalafil.
It is also important to remember that many people with thyroid conditions take other medicines (such as blood pressure tablets or antidepressants) that may interact with tadalafil. Your prescriber will review your full medication list during the consultation to ensure the combination is safe for you.
What Your Prescriber Will Check Before Approving Tadalafil and Liothyronine Together
When you request tadalafil through Cured Pharmacy's online consultation, the prescriber will ask about your current health, including your thyroid condition and any medicines you take. They will want to know whether your thyroid levels are stable and well controlled, as uncontrolled hyperthyroidism (overactive thyroid) or severe hypothyroidism can affect your heart and make ED treatment less safe [2].
The prescriber will also check for any other medicines that could interact with tadalafil. For example, if you take nitrates (such as GTN spray for angina), nicorandil, riociguat, or recreational drugs known as 'poppers', you must not take tadalafil, as the combination can cause a dangerous drop in blood pressure [3][4]. If you are on blood pressure medicines, alpha-blockers (for prostate symptoms), or certain antibiotics or antifungals, dose adjustments or extra caution may be needed.
You should also tell the prescriber about any heart problems, recent stroke or heart attack, very low blood pressure, or previous sudden vision or hearing loss. These conditions may mean tadalafil is not suitable, or that a lower dose should be used [4].
Declaring All Your Medicines and Supplements
Even if you think a medicine or supplement is unrelated to ED, it is essential to declare everything you take—including over-the-counter products, herbal remedies, and vitamins. For example, St John's wort (a herbal antidepressant) can reduce the effectiveness of tadalafil, and grapefruit juice can increase its levels in your blood [4]. Being open and thorough during your consultation helps the prescriber make the safest decision for you.
Declare All Your Medicines
Even if you think a medicine or supplement is unrelated, tell your prescriber about everything you take—including liothyronine, over-the-counter products, and herbal remedies. This helps ensure tadalafil is safe and effective for you.
Practical Advice for Taking Tadalafil and Liothyronine Safely
If your prescriber approves tadalafil, take it exactly as directed. For on-demand tadalafil, take one tablet at least 30 minutes before you plan to have sex; the effect can last up to 36 hours, so you do not need to rush [4]. For daily tadalafil, take one tablet at the same time each day, whether or not you plan to be sexually active. Do not take more than the prescribed dose, and never take tadalafil more than once in 24 hours.
Continue taking your liothyronine as prescribed by your doctor—do not stop or change the dose without medical advice. If you notice any new symptoms after starting tadalafil (such as dizziness, chest pain, palpitations, or unusual tiredness), contact your GP or pharmacist promptly. These could be signs that your thyroid levels need adjusting or that the combination is affecting your blood pressure or heart.
Avoid drinking large amounts of alcohol when taking tadalafil, as alcohol can worsen erectile dysfunction and increase the risk of dizziness or low blood pressure [4]. Grapefruit juice should also be avoided, as it can raise tadalafil levels in your blood. If you develop an erection lasting more than four hours, sudden loss of vision or hearing, or chest pain during sex, seek urgent medical help immediately.
When to See Your GP About Erectile Dysfunction and Thyroid Health
If you are experiencing erectile dysfunction for the first time, it is important to see your GP before seeking treatment online [1][2]. ED can be an early warning sign of underlying health problems such as heart disease, diabetes, or high blood pressure—all of which are more common in people with thyroid disorders. Your GP can arrange blood tests to check your thyroid function, blood sugar, cholesterol, and other markers of cardiovascular health.
If you are already taking liothyronine and your ED has worsened, or if you have symptoms such as chest pain, severe fatigue, rapid heartbeat, or unexplained weight changes, book an appointment with your doctor. These could indicate that your thyroid hormone levels need adjusting. Once your thyroid condition is stable, your GP or an online prescriber can discuss whether tadalafil or another ED treatment is appropriate for you.
Remember that ED is very common—it affects about half of men aged 40–70 to some degree [10]—and is almost always treatable. There is no need to feel embarrassed; seeking help is a positive step towards better health and quality of life.
Cured Pharmacy's Online Consultation Process
At Cured Pharmacy, all prescription medicines are supplied only after an online consultation reviewed by a UK-registered prescriber. The consultation asks about your medical history, current medicines (including liothyronine), and any symptoms or conditions that might affect the safety of tadalafil. If approved, your medicine is dispensed by our GPhC-registered pharmacy and delivered discreetly to your door. If tadalafil is not suitable, the prescriber will explain why and may suggest an alternative or advise you to see your GP.
When to get urgent help
- Erection lasting more than four hours (priapism)—go to A&E immediately
- Sudden loss of vision or hearing—stop tadalafil and seek urgent medical help
- Chest pain during or after sex—call 999; do not take more tadalafil
- Severe dizziness, fainting, or rapid heartbeat—contact your GP or call 111 for advice
- New or worsening symptoms after starting tadalafil—speak to your GP or pharmacist promptly
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 22 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 22 October 2026]
- Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 22 October 2026]
- Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 22 October 2026]
- Feldman, H. A., Goldstein, I., Hatzichristou, D. G., Krane, R. J., & McKinlay, J. B. (1994). Impotence and its medical and psychosocial correlates: Results of the Massachusetts Male Aging Study. Journal of Urology, 151(1), 54–61. https://pubmed.ncbi.nlm.nih.gov/8254833/ [accessed 22 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.
Trusted by thousands
Real people, real results
“Fabulous service and quick delivery”
“Felt the effects of these after about 5 days. Erections are better and can get aroused and ready easier”
“Excellent value and brilliant customer service”
“I received excellent service and everything went well. The order arrived quickly and in perfect condition. It's working very well! Thank you to the whole team for the great work!”
“Delivery was good, the product lived up to expectations.”
How Our Online Service Works
Get Discreet ED Treatment Online
Start your journey to better health today.
- Reviewed by UK-based prescribers
- Takes under 3 minutes
- Discreet Packaging
Start Your Journey To Better Health Today
Once you complete a short online assessment you will be able to choose your preferred treatment from safe medically approved options tailored to you.
Start My Assessment Log in to Your AccountYour Questions Answered
Can't find your answer? Our UK pharmacists review every consultation and can help.
Can I take tadalafil if I am on liothyronine for hypothyroidism?
Yes, in most cases tadalafil and liothyronine can be taken together safely, provided your thyroid levels are stable and your prescriber has reviewed your full medical history and current medicines.
Will liothyronine make tadalafil less effective?
No, liothyronine does not reduce the effectiveness of tadalafil. However, if your thyroid levels are not well controlled, this can affect your overall health and sexual function.
Do I need to take tadalafil and liothyronine at different times of day?
There is no need to separate the doses. Take each medicine as prescribed—liothyronine is usually taken once daily in the morning, and tadalafil can be taken on-demand or daily, depending on the regimen your prescriber recommends.
Can an overactive thyroid affect how tadalafil works?
Uncontrolled hyperthyroidism (overactive thyroid) can cause heart palpitations and high blood pressure, which may make tadalafil less safe. Your prescriber will check that your thyroid levels are stable before approving ED treatment.
What should I tell my prescriber about my thyroid condition?
Tell them which thyroid medicine you take, your current dose, when you last had blood tests, and whether your levels are stable. Also mention any symptoms such as palpitations, chest pain, or extreme tiredness.
Are there any ED medicines that are safer than tadalafil if I take liothyronine?
All PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil) have similar safety profiles with liothyronine. Your prescriber will help you choose the most suitable option based on your overall health and preferences.
Can I drink grapefruit juice if I take tadalafil and liothyronine?
Avoid grapefruit juice, as it can increase tadalafil levels in your blood and raise the risk of side effects. It does not significantly affect liothyronine.
What should I do if I feel dizzy or unwell after taking tadalafil with liothyronine?
Stop taking tadalafil and contact your GP or pharmacist. Dizziness could be a sign of low blood pressure or that your thyroid levels need adjusting.
Medically reviewed by
Tarun Kumar, Superintendent Pharmacist (GPhC 2233073)