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Tadalafil, otherwise known as Cialis®, is one of the most widely prescribed medications for erectile dysfunction (ED), which is much more common than people think.
While most men handle the medication well, like any other prescription medication, it can have significant side effects along with the benefits, so it's important to know what they are before you start treatment.
This guide takes an in-depth look into what tadalafil is, how it works, what to be cautious about, and how to use it safely.
Tadalafil can only be obtained with a prescription and belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. It's nicknamed “the weekend pill” because it's long-lasting, unlike some other ED medications; a single dose can be effective for up to 36 hours (Costa et al., 2009).
If you're considering taking tadalafil, concierge services like Feel30 provide it under the guidance of expert medical professionals.
Tadalafil is FDA-approved to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BPH) under the brand name Cialis, as well as pulmonary arterial hypertension (PAH) under the brand name Adcirca. It helps treat the symptoms of erectile dysfunction but does not address the underlying cause, which may require additional evaluation and treatment. In some men, erectile dysfunction can occur alongside low testosterone symptoms, such as reduced libido, fatigue, or changes in mood.
Tadalafil is prescribed for is:
First of all, tadalafil only works in response to sexual stimulation. In other words, taking the medication on its own will not automatically cause an erection.
During sexual arousal, the body automatically releases chemicals that relax the blood vessels of the penis, allowing blood to flow and resulting in an erection. Then, an enzyme known as PDE5 breaks down the chemicals, causing the erection to fade. Tadalafil's job is to block this enzyme, keeping blood vessels relaxed for longer and improving blood flow, making it easier to maintain an erection (Fahmy & Hess, 2024).
To learn more about ED, read Feel30's guide on Understanding Erectile Dysfunction Symptoms.
Even though tadalafil is safe for most healthy men, it isn't a good option for everyone; depending on your symptoms and medical history, additional testing may be recommended before starting.
You should not take tadalafil (Fahmy & Hess, 2024) if you:
Sometimes, your medical provider will recommend you don't take tadalafil (or will monitor you more closely) if you have:
The National Institutes of Health (2025) says tadalafil can interact with certain medications, which can make side effects worse or reduce its effectiveness overall, for example:
Some medical conditions can affect how tadalafil works in the body.
If you have kidney issues, liver or cardiovascular disease, diabetes, a bleeding disorder, or an active stomach ulcer, your doctor might adjust your dose or monitor you more closely. Alcohol can increase the risk of certain side effects like low blood pressure, dizziness, headaches, and fainting when consumed in large amounts. Always tell your healthcare provider about all prescription medications, over-the-counter medicines, and supplements you take before starting tadalafil.
Experts recommend taking tadalafil exactly as it's been prescribed. For erectile dysfunction, it is taken on a once-daily or as-needed basis. If you're wondering how long does tadalafil take to work, the timing can vary depending on the individual.
Most men take it approximately 30 minutes before sexual activity, but some prefer to take a lower dose daily to allow for more spontaneity. It can last for up to 36 hours, depending on the individual (NHS, 2026). Learn more about how daily Cialis works and who it may suit.
[Image by Staff, Canva].
Side effects from tadalafil are usually mild particularly when starting treatment, but if they persist or become bothersome, speak to your healthcare provider. However, it's important to be able to differentiate between common and serious side effects.
If any of these rare side effects persist, get worse, or happen suddenly, contact your healthcare provider.
Serious side effects, such as a painful erection that lasts more than four hours; sudden loss of vision; or a severe allergic reaction, including hives, swelling of the face or throat, or difficulty breathing, are rare, but do require you to see a doctor immediately if they occur (Eli Lilly and Company, 2024).
[Image by Staff, Canva].
For most people, tadalafil is a safe and effective medication when used with medical supervision (Burnett et al., 2018); however, all prescription medication comes with risks. Whether you'll experience generally mild or adverse side effects depends on your age, the dose you're on, what other medication you take, and whether you have another underlying medical condition. To be safe, prioritize your sexual health and address erectile dysfunction with clinically proven ED treatments; ensure you get tadalafil from a reputable, qualified healthcare provider, such as Feel30, who does a thorough assessment of your health before beginning treatment.
Viagra, or its generic, sildenafil, belongs to the same class of drugs as tadalafil, so neither is safer than the other. They have many similar possible side effects, such as headaches, indigestion, nasal congestion, and flushing.
The difference lies in how long the effects last: Tadalafil lasts up to 36 hours, while sildenafil lasts about 4 to 6 hours. Some men prefer once-daily dosing with tadalafil, while others prefer sildenafil. Finding the right solution depends on your lifestyle, health, and your doctor's recommendations (Gong et al., 2017).
Not unless your doctor has prescribed this dose. Current clinical guidelines (Fahmy & Hess, 2024) recommend a daily dose of 2.5-5 mg. The higher strength 10 mg or 20 mg pills are usually used when taken as needed and not every day. Higher doses may increase the risk of side effects and should only be used if recommended by your healthcare provider.
There is a belief that if you eat grapefruit or drink grapefruit juice, it can help with ED due to certain compounds it contains, but there is no credible evidence to support this claim.
In fact, grapefruit juice could increase the amount of tadalafil in the blood, which could in turn increase the risk of side effects like headaches, dizziness, low blood pressure, and fainting, so it's important to talk to your healthcare provider if you regularly consume grapefruit or grapefruit juice while taking tadalafil (NHS, 2026).
Proven treatments, such as tadalafil, are the safer and more effective option.
If you're taking tadalafil on an as-needed basis, there isn't a missed-dose schedule. Simply take it before sexual activity as directed, and do not take more than prescribed. If you're taking it once daily and you miss a dose, take it as soon as you remember, but if it's almost time for your next dose, skip the missed dose altogether and carry on with your normal dosing. Never double up on doses.
Serious complications from tadalafil are very rare, and most people tolerate the medication well when it is used as prescribed.
There are two very rare but severe side effects that need immediate medical care: priapism (a prolonged erection) and NAION (non-arteritic anterior ischemic optic neuropathy), or sudden vision loss.
A prolonged erection can result in permanent tissue damage because blood becomes trapped in the tissue and is deprived of oxygen. That's why it needs to be treated promptly (Huang et al., 2009).
Sudden vision loss occurs when blood flow to the optic nerve is abruptly cut off. This can cause sudden, painless vision loss in one or both eyes, which can result in permanent blindness (Barosso et al., 2021).
The key to managing erectile dysfunction safely is working with a qualified healthcare provider who can evaluate the underlying cause of erectile dysfunction, review your medical history and medications, and determine whether tadalafil is appropriate for you. Most men experience mild, temporary side effects.
For many people, tadalafil is an effective and well-tolerated treatment when prescribed appropriately and used under medical supervision. Services like Feel30 offer access to licensed healthcare professionals who can evaluate whether tadalafil is appropriate and develop an individualized treatment plan when clinically indicated.
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