Key takeaways:
Viagra (sildenafil) is an oral medication that treats erectile dysfunction. A typical dosage is to take 50 mg about an hour before sexual activity.
Viagra should never be taken with nitrates or riociguat (Adempas). People with uncontrolled heart problems or rare eye conditions may also need to avoid Viagra in certain cases.
Adults ages 65 years and older, and some people with liver or kidney problems, have a higher risk of experiencing Viagra side effects. It’s recommended to start with a lower 25 mg dose in these cases.
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Growing older means a growing chance of developing certain health conditions. Erectile dysfunction (ED) is a case in point. ED is more common after age 50, and it can become riskier to take certain ED treatments as you get older.
Viagra (sildenafil) is one treatment that sometimes raises this concern. Viagra and other phosphodiesterase-5 (PDE-5) inhibitors are first-choice medications for ED. Viagra comes as an oral pill you take about an hour before sexual activity — but you can take it anywhere from 30 minutes to 4 hours before sex.
Viagra works by relaxing your blood vessels and improving blood flow to your penis when you’re sexually aroused. It’s generally safe, but it can cause side effects such as blood pressure changes and skin flushing. Some people, including older adults, may be especially prone to these risks.
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Can older adults take Viagra?
Yes, but it’s recommended to start with a lower dose.
The typical starting dosage of Viagra is one 50 mg tablet about an hour before sexual activity. But for adults over age 65, it’s recommended to start with a lower 25 mg dose. Compared to younger people, Viagra leaves the body more slowly in older adults. A lower dose can help reduce the risk of side effects, such as flushing and nose bleeds.
If you’re able to tolerate Viagra and you feel that you need a higher dose later on, you can work with your healthcare professional to safely adjust it upwards.
Who shouldn’t take Viagra?
Certain people shouldn’t take Viagra at all. A handful of interacting medications make it too risky to take Viagra. In other cases, you may be able to take Viagra with extra precautions in place. You may be told to take a lower dose or follow up frequently with your healthcare professional.
1. People taking certain medications
Some drug interactions are especially risky with Viagra.
People who are taking nitrates — such as isosorbide dinitrate (Isordil) or nitroglycerin (Nitrostat) — for a heart problem should not take Viagra or another PDE-5 inhibitor. This combination is dangerous and can cause severe hypotension (low blood pressure).
Guanylate cyclase stimulators such as riociguat (Adempas) also interact with Viagra. It’s important to avoid this combination because they raise the risk for excessively low blood pressure, too. Alpha blockers such as doxazosin (Cardura) cause similar effects, but you may not need to avoid them altogether.
Another interacting medication is ritonavir, which can block the breakdown of Viagra and raise how much is in the body. This can lead to additional Viagra side effects. Ritonavir is found in Paxlovid, the popular COVID-19 pill, and certain hepatitis C and HIV treatments. Your healthcare professional will usually lower your Viagra dose, and maybe have you space them further apart too.
Keep in mind: Other medications may interact with Viagra. Make sure your prescriber and pharmacist have your updated medication list.
2. People with recent heart problems
People with heart problems often experience ED. This includes conditions such as heart failure, a previous heart attack, or an irregular heartbeat. These conditions can affect how your blood circulates in your body; this can interfere with adequate blood flow to the penis.
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Recommended dosages: Viagra is an oral pill that you take as needed before sex. Pharmacists review what you should know about typical Viagra dosages.
Wondering about side effects? Read on for some of the most common Viagra side effects — from headaches to low blood pressure — and how to manage them.
If sexual activity is safe for your heart but you struggle with ED, medications like Viagra can help improve quality of life and relationship satisfaction. But it’s not safe for everyone.
If you had a heart attack, stroke, or life-threatening arrhythmia (heart rhythm problem) in the last 6 months, your prescriber will likely want you to steer clear of Viagra. This is also true if you actively have chest pain, a heart obstruction, or uncontrolled blood pressure. This is done to help prevent potentially dangerous heart or blood pressure changes.
However, there is some good news. If your blood pressure is being managed or you have stable heart disease, you should be able to take Viagra.
3. People with rare eye conditions
There have been some reports of Viagra causing vision issues, particularly with higher doses. Blurred vision, light sensitivity, and color changes have all been linked. In these cases, vision typically returned to normal after several weeks.
People with rare eye conditions — such as non-arteritic anterior ischemic optic neuropathy (NAION) or retinitis pigmentosa — may be more likely to develop eye-related side effects after taking Viagra. If you have eye problems such as these, your prescriber may want you to avoid Viagra. Not taking more than your recommended dose can also help keep you safe.
If you experience sudden blurriness or loss of vision after starting Viagra, get medical care right away. Your healthcare professional will likely recommend stopping Viagra to avoid further issues.
4. People with kidney or liver problems
People with liver issues or severe kidney problems may need a lower dose of Viagra. Your liver and kidneys help break down and remove many medications from your body. If they’re not working as well as possible, Viagra might not leave your body in a timely manner. This raises the risk of side effects.
Talk to your healthcare professional about the health of your liver and kidneys. They can tell you whether a dose adjustment to Viagra 25 mg is necessary. In some cases, they may want you to avoid it as a precaution.
5. People who are allergic to Viagra
As with other medications, it’s possible for Viagra to cause an allergic reaction. An allergic reaction can range anywhere from an itchy rash to hives or even anaphylaxis.
Allergies to Viagra are rare. And more generally, allergic reactions to medications aren’t common — only 5% to 10% of reactions are from a true allergy. Most reactions are from side effects, which is when your body doesn’t tolerate a medication well but doesn’t necessarily think it’s an allergen. To play it safe, talk to your healthcare professional if you experience a questionable reaction after starting Viagra.
People with true allergies to Viagra should not try taking it again. Your healthcare professional can suggest another option, such as alprostadil, that’s different enough to avoid triggering an allergic reaction.
6. People at risk for painful erections
Rare cases of priapism — painful erections lasting more than 4 hours — have been reported with Viagra. People who have an increased risk for priapism should be careful when taking Viagra. This includes people with sickle cell anemia, leukemia, and multiple myeloma. People who have Peyronie’s disease — or other conditions involving structural changes to the penis — should also heed caution.
To avoid serious complications, seek emergency medical attention for an erection lasting more than 4 hours.
Who is the best candidate to take Viagra?
Viagra is generally safe for men with ED. Men without any history of heart problems, eye issues, or a Viagra allergy are the best candidates to take it. In these cases, the recommended starting dose is 50 mg before sexual activity. If it’s not doing enough, your healthcare professional may recommend raising the dose to 100 mg as needed.
Viagra alternatives
If you have ED and aren’t a good candidate to take Viagra, ask your healthcare professional if any Viagra alternatives would be a safer option. These choices include:
Alprostadil (Caverject, Edex) injections
BiMix (papaverine, phentolamine)
TriMix (papaverine, phentolamine, alprostadil)
QuadMix (papaverine, phentolamine, alprostadil, atropine)
Supplements like ginseng or yohimbine
ED devices like vacuum pumps and tension rings
Frequently asked questions
Viagra isn’t meant to be taken daily. Most of the time, it’s taken only when needed for ED. If you want or need to take ED medication every day, Cialis (tadalafil) would likely be a better option.
In some cases, a healthcare professional may recommend taking a different form of sildenafil every day to treat pulmonary arterial hypertension.
In many cases, yes. But this depends on which medication(s) you take and your overall health. Viagra can lower blood pressure, so combining it with certain blood pressure drugs — especially nitrates or alpha blockers — can cause dizziness, fainting, or weakness. Never take Viagra with nitrates, and use caution when taking it with alpha blockers, such as doxazosin. Don’t change your doses without talking to your healthcare team, either.
If you’re taking blood pressure medication and considering Viagra, your prescriber can help you find the safest dose and watch for side effects. They can also tell you how often to monitor your blood pressure.
Viagra isn’t meant to be taken daily. Most of the time, it’s taken only when needed for ED. If you want or need to take ED medication every day, Cialis (tadalafil) would likely be a better option.
In some cases, a healthcare professional may recommend taking a different form of sildenafil every day to treat pulmonary arterial hypertension.
In many cases, yes. But this depends on which medication(s) you take and your overall health. Viagra can lower blood pressure, so combining it with certain blood pressure drugs — especially nitrates or alpha blockers — can cause dizziness, fainting, or weakness. Never take Viagra with nitrates, and use caution when taking it with alpha blockers, such as doxazosin. Don’t change your doses without talking to your healthcare team, either.
If you’re taking blood pressure medication and considering Viagra, your prescriber can help you find the safest dose and watch for side effects. They can also tell you how often to monitor your blood pressure.
The bottom line
People who take nitrates, riociguat (Adempas), or are allergic to sildenafil should avoid taking Viagra. Adults ages 65 years and older and those with heart, liver, or kidney problems should generally use extra caution while taking it. If you’re interested in taking Viagra, your healthcare professional can help you decide if it’s a good fit.
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References
American Academy of Allergy, Asthma & Immunology. (2023). Medications and drug allergic reactions.
Aurobindo Pharma Limited. (2023). Sildenafil- sildenafil tablet, film coated [package insert].
Ausó, E., et al. (2021). Visual side effects linked to sildenafil consumption: An update. Biomedicines.
Burnett, A. L., et al. (2018). Erectile dysfunction: AUA guideline. The Journal of Urology.
Cestari, D., et al. (2025). Non-arteritic anterior ischemic optic neuropathy (NAION). American Academy of Ophthalmology.
Karaarslan, C. (2020). Ocular side effects of sildenafil that persist beyond 24 h—a case series. Frontiers in Neurology.
National Eye Institute. (2025). Retinitis pigmentosa. National Institutes of Health.
Roy, S., et al. (2021). Cardiac effects of phosphodiesterase-5 inhibitors: Efficacy and safety. Cardiovascular Drugs and Therapy.
