Tadalafil and Ferrous Sulfate: Can You Take Them Together?

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What is tadalafil and ferrous sulfate used for?

Tadalafil is a prescription 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 increased blood flow when you are sexually aroused [4]. Tadalafil is available as on-demand tablets (10mg or 20mg, taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose tablet (2.5mg or 5mg). It requires sexual stimulation to work and does not increase sexual desire on its own.

Ferrous sulfate is an iron supplement commonly prescribed to treat or prevent iron-deficiency anaemia, a condition where your blood does not have enough healthy red blood cells due to low iron levels. Iron is essential for making haemoglobin, the protein in red blood cells that carries oxygen around your body. Ferrous sulfate is usually taken once or twice daily, often on an empty stomach to improve absorption, though it can be taken with food if it causes stomach upset.

Is there an interaction between tadalafil and ferrous sulfate?

No major interaction is commonly reported between tadalafil and ferrous sulfate. These two medicines work in different ways and are processed by your body through different pathways, so taking them together does not usually cause problems. Tadalafil is metabolised primarily by the liver enzyme CYP3A4, while ferrous sulfate is absorbed in the gut and does not significantly affect liver enzymes or blood pressure.

However, it is important to remember that your prescriber will review all your current medicines, supplements, and health conditions during your online consultation before prescribing tadalafil. This comprehensive check ensures that tadalafil is safe and suitable for you, taking into account your full medical picture. Even though ferrous sulfate itself does not interact with tadalafil, other medicines you may be taking could, so always declare everything you are using.

Why iron supplements are prescribed

Iron-deficiency anaemia can cause fatigue, weakness, shortness of breath, and pale skin. It may result from inadequate dietary iron, blood loss (such as heavy periods or gastrointestinal bleeding), or increased iron needs during pregnancy. Your GP will usually diagnose anaemia with a blood test and prescribe ferrous sulfate or another iron supplement to restore your iron levels. Treatment typically lasts several months, even after symptoms improve, to replenish your body's iron stores.

When to get urgent help

• Erection lasting more than 4 hours – call 999 or go to A&E immediately
• Sudden loss of vision in one or both eyes – seek emergency medical help
• Chest pain during or after sexual activity – stop and call 999
• Severe dizziness, fainting, or rapid heartbeat after taking tadalafil – contact GP or call NHS 111
• Sudden decrease or loss of hearing, possibly with ringing in ears – seek urgent medical advice

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

What does your prescriber check before prescribing tadalafil?

Before prescribing tadalafil, your prescriber will ask about your current medicines, medical history, and overall health. They need to ensure tadalafil is safe for you and that sexual activity itself is advisable. Key checks include your blood pressure, heart health, and any history of stroke, heart attack, or severe heart failure. Tadalafil is not suitable if you have very low blood pressure, unstable angina, or if you have had a heart attack or stroke in the past six months [4].

Your prescriber will also check for medicines that must never be taken with tadalafil. Do not take tadalafil together with nitrates (such as GTN spray, isosorbide mononitrate, or isosorbide dinitrate), nicorandil, riociguat, amyl or alkyl nitrites (poppers), or another PDE5 inhibitor. These combinations can cause a dangerous drop in blood pressure [4]. If you take alpha-blockers (such as doxazosin or tamsulosin for prostate symptoms), your prescriber will ensure you are stable on that medicine and start you on the lowest dose of tadalafil to minimise the risk of dizziness or fainting.

Certain medicines that affect liver enzymes can alter how tadalafil works. Potent CYP3A4 inhibitors (such as ritonavir, ketoconazole, itraconazole, or clarithromycin) can raise tadalafil levels, so your prescriber may adjust your dose. Conversely, CYP3A4 inducers (such as rifampicin, carbamazepine, phenytoin, or St John's wort) can reduce tadalafil's effectiveness. Your prescriber will review all these factors during your consultation to ensure tadalafil is both safe and likely to work well for you.

Practical advice for taking tadalafil and ferrous sulfate together

If you are taking both tadalafil and ferrous sulfate, you can generally take them at times that suit you, as they do not need to be separated. However, ferrous sulfate is best absorbed on an empty stomach (about one hour before food or two hours after), though you may take it with food if it upsets your stomach. Tadalafil can be taken with or without food, though a very heavy, high-fat meal may slightly delay its effect.

Continue taking your ferrous sulfate exactly as your doctor has prescribed, even if you feel better, to ensure your iron stores are fully replenished. Do not stop or change the dose of any prescribed medicine without consulting your GP or pharmacist. If you experience any new or unusual symptoms after starting tadalafil, contact your prescriber or pharmacist for advice.

Avoid drinking large amounts of alcohol when taking tadalafil, as alcohol can worsen erectile dysfunction and add to the blood-pressure-lowering effect, increasing the risk of dizziness or fainting. Grapefruit juice can raise tadalafil levels in your blood, so it is best to avoid it. If you are taking other medicines for blood pressure or heart conditions, be aware that tadalafil may add to their effect, so report any dizziness or light-headedness to your healthcare professional.

Tips for taking iron supplements

Ferrous sulfate can cause side effects such as constipation, nausea, stomach pain, or dark stools (which is harmless). Taking it with orange juice or vitamin C can improve absorption, while tea, coffee, and calcium-rich foods (such as dairy) can reduce absorption. If side effects are troublesome, speak to your GP, who may suggest a lower dose, a different iron preparation, or taking it on alternate days.

At a glance

Warning signs and when to seek help with tadalafil and ferrous sulfate

While tadalafil and ferrous sulfate can usually be taken together without problems, you should be aware of warning signs that need urgent medical attention. If you experience an erection lasting more than four hours (priapism), seek emergency help immediately by calling 999 or going to A&E. Priapism can damage the penis permanently if not treated promptly [4].

Seek urgent medical help if you develop sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing, which may be accompanied by ringing in the ears or dizziness. These are rare but serious side effects of PDE5 inhibitors [4]. If you experience chest pain during or after sexual activity, stop and seek medical advice straight away, as this may indicate a heart problem.

If you develop severe dizziness, fainting, or a rapid heartbeat after taking tadalafil, especially if you are also taking blood-pressure medicines or alpha-blockers, contact your GP or call NHS 111 for advice. These symptoms may suggest your blood pressure has dropped too low. Remember, your prescriber will have checked your medicines and health conditions before prescribing tadalafil, but always report any new or worsening symptoms.

Other medicines and supplements to discuss with your prescriber

In addition to ferrous sulfate, you may be taking other medicines or supplements. Always tell your prescriber about everything you use, including over-the-counter medicines, herbal remedies, vitamins, and recreational drugs. Some medicines can interact with tadalafil, affecting how well it works or increasing the risk of side effects.

If you take medicines for high blood pressure, heart disease, or prostate problems, your prescriber will check these carefully. Alpha-blockers (such as tamsulosin, doxazosin, alfuzosin, or terazosin) can interact with tadalafil, causing low blood pressure and dizziness, so you must be stable on the alpha-blocker and start on the lowest dose of tadalafil [4]. Other blood-pressure medicines may also add to tadalafil's blood-pressure-lowering effect, but this is usually manageable with careful prescribing.

Certain antibiotics (such as clarithromycin or erythromycin), antifungals (such as ketoconazole or itraconazole), and HIV medicines (such as ritonavir or cobicistat) can raise tadalafil levels, so your prescriber may adjust your dose. St John's wort, a herbal remedy for low mood, can reduce tadalafil's effectiveness. If you are unsure whether a medicine or supplement interacts with tadalafil, ask your prescriber or pharmacist during your consultation. Do not stop or change any prescribed medicine without professional advice.

Why you should see your GP for 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 underlying health conditions such as heart disease, diabetes, high blood pressure, or high cholesterol [1]. Your GP can arrange blood tests and checks to identify and treat any underlying causes, which may improve your ED and protect your long-term health. Treating ED with medicines like tadalafil is effective, but addressing the root cause is equally important.

In summary

• No major interaction is commonly reported between tadalafil and ferrous sulfate
• Your prescriber checks all medicines during consultation to ensure tadalafil is safe for you
• Never take tadalafil with nitrates, nicorandil, riociguat, poppers, or another PDE5 inhibitor
• Seek urgent help for erections lasting over 4 hours or sudden vision or hearing loss
• Always declare all medicines, supplements, and health conditions during your consultation

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