Vardenafil and Levothyroxine: Can You Take Them Together?

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At a glance

What Is Vardenafil and How Does It Work?

Vardenafil is a prescription medicine used to treat erectile dysfunction (ED) in adult men. It belongs to a group of medicines called PDE5 inhibitors, which also includes sildenafil (Viagra), tadalafil (Cialis), and avanafil (Spedra) [5]. Vardenafil works by relaxing the blood vessels in the penis, allowing more blood to flow in when you are sexually aroused. This helps you get and keep an erection suitable for sexual activity [5].

Vardenafil is available in 5 mg, 10 mg, and 20 mg tablets. The usual starting dose is 10 mg, taken about 25 to 60 minutes before sexual activity [5]. You should not take vardenafil more than once a day. It only works when you are sexually stimulated—it will not cause an erection on its own. The medicine is broken down mainly by the liver, using an enzyme system called CYP3A4, which is important when considering interactions with other medicines [5].

At Cured Pharmacy, vardenafil is available on prescription after an online consultation reviewed by a UK prescriber. This ensures the medicine is safe and suitable for you, taking into account your medical history and any other medicines you are taking.

What Is Levothyroxine and Why Is It Prescribed?

Levothyroxine is a thyroid hormone replacement medicine used to treat an underactive thyroid gland (hypothyroidism). When your thyroid does not produce enough thyroid hormone, you may experience symptoms such as tiredness, weight gain, feeling cold, dry skin, and sometimes erectile dysfunction [1]. Levothyroxine replaces the missing hormone and helps restore normal metabolism and energy levels.

Levothyroxine is usually taken once a day, ideally on an empty stomach at least 30 minutes before breakfast, to ensure it is absorbed properly. It is a long-term treatment, and most people take it for life. Your GP or endocrinologist will monitor your thyroid function with regular blood tests to make sure your dose is correct.

Thyroid problems, including both underactive and overactive thyroid, can contribute to erectile dysfunction [1]. Treating hypothyroidism with levothyroxine may improve ED symptoms in some men, but additional treatment such as a PDE5 inhibitor like vardenafil may still be needed. It is important to tell your prescriber about your thyroid condition and levothyroxine dose during your ED consultation.

Can Thyroid Problems Cause Erectile Dysfunction?

Yes, thyroid disorders are a recognised cause of erectile dysfunction [1]. An underactive thyroid can lead to low energy, reduced libido, and hormonal imbalances that affect sexual function. Treating the thyroid condition with levothyroxine often helps, but ED may persist and require specific treatment. Your prescriber will consider your thyroid health as part of the overall assessment when prescribing vardenafil or another ED medicine.

Do Vardenafil and Levothyroxine Interact?

There is no commonly reported direct pharmacological interaction between vardenafil and levothyroxine. These two medicines work in different ways and are processed differently by the body. Levothyroxine replaces thyroid hormone, while vardenafil acts on blood vessels in the penis. They do not interfere with each other's absorption or breakdown in a clinically significant way.

However, it is still essential to declare all your current medicines, including levothyroxine, during your online consultation. Your prescriber needs to understand your full medical picture, including your thyroid condition, to ensure vardenafil is safe for you. Uncontrolled thyroid disease, particularly hyperthyroidism (overactive thyroid), can affect your heart and blood pressure, which are important considerations when prescribing any PDE5 inhibitor [5].

If your thyroid condition is well controlled on levothyroxine and you have no other contraindications, vardenafil can usually be prescribed safely. Your prescriber will check for any other medicines or health conditions that might interact with vardenafil, such as nitrates, alpha-blockers, or potent CYP3A4 inhibitors [5]. Always be honest and thorough when completing your consultation form.

What you need to know

• No major direct interaction exists between vardenafil and levothyroxine in clinical practice.
• Always declare your thyroid medication and condition during your ED consultation.
• Thyroid problems can contribute to erectile dysfunction; treating them may help.
• Never take vardenafil with nitrates, nicorandil, riociguat, poppers, or another PDE5 inhibitor.
• Your prescriber checks all your medicines and health conditions before prescribing vardenafil.

What Does Your Prescriber Check Before Prescribing Vardenafil?

Before prescribing vardenafil, your prescriber will review your full medical history and current medicines to ensure the treatment is safe [2]. They will check for any absolute contraindications, such as use of nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs called poppers (amyl or alkyl nitrites). Taking vardenafil with any of these can cause a dangerous drop in blood pressure and must never be done [5].

Your prescriber will also ask about cardiovascular conditions, including recent heart attack or stroke, unstable angina, severe heart failure, or very low blood pressure, as these may make sexual activity inadvisable [5]. They will check whether you take alpha-blockers (such as doxazosin or tamsulosin) for prostate or blood pressure problems, as these can interact with vardenafil and cause dizziness or fainting. If you are on an alpha-blocker, you must be stable on it and start vardenafil at the lowest dose [5].

Medicines that strongly inhibit the CYP3A4 enzyme—such as ritonavir, cobicistat, ketoconazole, itraconazole, or clarithromycin—can raise vardenafil levels in the blood. Vardenafil is contraindicated or requires dose adjustment with these medicines, so your prescriber will check the summary of product characteristics (SmPC) if you take any of them [5]. Your thyroid medication, levothyroxine, will be noted, and your prescriber will confirm your thyroid condition is stable.

Other Medicines That May Affect Vardenafil

CYP3A4 inducers, such as rifampicin, carbamazepine, phenytoin, and St John's wort, can reduce vardenafil levels and make it less effective [5]. Other blood-pressure-lowering medicines can add to the blood-pressure effect of vardenafil, potentially causing dizziness, though this is usually manageable. Grapefruit juice can also raise vardenafil levels and should be avoided. Always declare every medicine, supplement, and herbal product you use during your consultation.

Practical Advice for Taking Vardenafil with Levothyroxine

If you are prescribed vardenafil while taking levothyroxine, continue taking your thyroid medicine exactly as directed by your GP or endocrinologist. Do not stop or change your levothyroxine dose without medical advice. Take levothyroxine on an empty stomach, ideally first thing in the morning, at least 30 minutes before food, to ensure good absorption.

Vardenafil should be taken about 25 to 60 minutes before you plan to have sex [5]. You can take it with or without food, though a very heavy or high-fat meal may delay its effect. Do not take more than one dose of vardenafil in 24 hours. Sexual stimulation is needed for the medicine to work—it will not cause an automatic erection.

Monitor how you feel when you first start vardenafil. Some men experience mild side effects such as headache, flushing, indigestion, or a stuffy nose [5]. These are usually temporary. If you feel dizzy or light-headed, sit or lie down and avoid driving or operating machinery. If you experience chest pain during sex, stop and seek urgent medical help. Do not use nitrate medicines (such as GTN spray) to treat chest pain if you have taken vardenafil, as this combination is dangerous [5].

When to get urgent help

• Erection lasting longer than 4 hours (priapism) – go to A&E immediately
• Sudden loss of vision in one or both eyes – seek urgent medical help
• Sudden decrease or loss of hearing – contact your GP or call 111 urgently
• Chest pain during or after sex – call 999; do not use GTN spray if you have taken vardenafil
• Severe dizziness, fainting, or very fast or irregular heartbeat – seek immediate medical attention

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

When to Seek Medical Advice About Vardenafil and Levothyroxine

Seek urgent medical help if you develop an erection that lasts longer than four hours (priapism), sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing [5]. These are rare but serious side effects that require immediate attention. If you experience chest pain, severe dizziness, or fainting after taking vardenafil, call 999 or go to A&E.

Contact your GP if your erectile dysfunction does not improve with vardenafil, or if you develop new symptoms such as persistent tiredness, weight changes, or palpitations, which could indicate a change in your thyroid condition. Your GP may want to check your thyroid function tests and adjust your levothyroxine dose if needed.

If you are prescribed a new medicine by another doctor or buy an over-the-counter product, check with your pharmacist or GP whether it is safe to take with vardenafil. Never take another PDE5 inhibitor (such as sildenafil or tadalafil) at the same time as vardenafil. If you want to switch to a different ED medicine, discuss this with your prescriber during your next consultation. At Cured Pharmacy, our UK prescribers are available to review your treatment and answer any questions you may have.

Lifestyle Tips to Support ED Treatment

Alongside medication, lifestyle changes can improve erectile function and overall health [1][2]. Maintain a healthy weight, eat a balanced diet, exercise regularly, limit alcohol, and stop smoking. Managing stress and getting enough sleep also help. If your thyroid condition is well controlled with levothyroxine and you adopt healthy habits, you are more likely to see good results from vardenafil or other ED treatments.