Can You Take Viagra With Blood Thinners?

Blood thinners are not among the drugs the Viagra label says you must never combine with it. The ones it rules out are nitrates, such as nitroglycerin, and guanylate cyclase stimulators such as riociguat (VIAGRA label, 2026). The label does flag gaps in what is known about bleeding, so if you take an anticoagulant, decide with the clinician who prescribes it.

Viagra is sildenafil, a PDE5 inhibitor (a drug that relaxes blood vessel walls by blocking the enzyme phosphodiesterase type 5). In healthy volunteers it briefly lowered lying-down blood pressure by an average maximum of 8.4/5.5 mmHg (VIAGRA label, 2026).

What does the Viagra label say about bleeding?

In people, Viagra had no effect on bleeding time (how long a small standard cut takes to stop bleeding), whether taken alone or with aspirin. In one study, 50 mg of Viagra did not add to the rise in bleeding time caused by 150 mg of aspirin (VIAGRA label, 2026).

Two findings point the other way, and neither comes from people taking blood thinners. In lab studies with human platelets (the cells that clump to start a clot), sildenafil strengthened the anti-clumping effect of sodium nitroprusside, a nitric oxide donor. In anesthetized rabbits, heparin and Viagra together lengthened bleeding time more than either alone; the label says this has not been studied in humans (VIAGRA label, 2026).

Bleeding events have been reported in people who took Viagra after it reached the market, and nosebleeds appear on the label's list of postmarketing reports. These reports are voluntary, so the label cannot give a rate, and it says a causal link to Viagra has not been established (VIAGRA label, 2026).

The safety of Viagra is unknown in people with bleeding disorders and in people with an active peptic ulcer (VIAGRA label, 2026).

What about warfarin and newer anticoagulants?

In the label's drug interaction studies, warfarin (40 mg) showed no significant interaction with sildenafil. Trial data also showed warfarin did not change how the body handles sildenafil (VIAGRA label, 2026).

The label does not report bleeding outcomes in men who take an anticoagulant every day, and it reports no studies at all with apixaban (Eliquis), rivaroxaban (Xarelto), dabigatran (Pradaxa), or clopidogrel (Plavix). For those drugs, the label offers no data either way.

Which drugs does the label rule out?

The label lists three contraindications (situations where the drug must not be used) (VIAGRA label, 2026):

• Nitrates in any form, taken regularly or only now and then, because Viagra strengthens their blood-pressure-lowering effect. That includes nitroglycerin for chest pain (angina) and the street drugs called "poppers" (amyl nitrite, amyl nitrate, or butyl nitrate). After a dose of Viagra, it is unknown when a nitrate can be given safely.
• Guanylate cyclase stimulators such as riociguat (Adempas), which treats pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Viagra may deepen their blood pressure drop too.
• An allergy to sildenafil or any ingredient in the tablet.

Cialis (tadalafil) carries the same nitrate and riociguat contraindications. Its label says that if a nitrate becomes medically necessary in a life-threatening situation, at least 48 hours should pass after the last Cialis dose first, with close medical monitoring (CIALIS label, 2026).

Which other drugs and conditions need caution?

These are not outright bans, but the label asks prescribers to weigh them (VIAGRA label, 2026).

Alpha-blockers such as tamsulosin (Flomax) or doxazosin (Cardura) are often prescribed for prostate symptoms. They and Viagra both lower blood pressure, and together they can cause dizziness or fainting. The label says to be stable on the alpha-blocker before starting Viagra, and to start Viagra at the lowest dose.

Blood pressure medicines add to the drop. In hypertensive patients taking amlodipine, a 100 mg dose of Viagra lowered blood pressure by a further 8 mmHg systolic and 7 mmHg diastolic on average.

Drugs that block the liver enzyme CYP3A4 raise sildenafil levels. Ritonavir, an HIV drug, increased total sildenafil exposure 11-fold, and saquinavir or erythromycin raised levels about 3-fold. The label recommends a lower Viagra dose with these drugs.

Combining Viagra with another ED treatment, including a second PDE5 inhibitor, has not been studied and may lower blood pressure further, so the label does not recommend it.

The label also covers heart conditions. ED drugs should not generally be used by men for whom sexual activity is inadvisable because of their heart. The label has no controlled data in men who had a heart attack, stroke, or life-threatening arrhythmia in the last 6 months, men with resting blood pressure below 90/50 or above 170/110 mmHg, or men with heart failure or unstable angina. If you take a blood thinner for a heart condition, this part of the label may matter more to you than the bleeding section.

What side effects does Viagra cause?

In placebo-controlled trials lasting 2 to 26 weeks where men took Viagra as needed, the most common side effects were (VIAGRA label, 2026):

• Headache: 16% with Viagra vs 4% with placebo
• Flushing: 10% vs 1%
• Indigestion: 7% vs 2%
• Stuffy nose: 4% vs 2%
• Vision changes, mostly a color tinge, light sensitivity, or blurring: 3% vs 0%

Three rare effects need urgent care (VIAGRA label, 2026):

• An erection lasting more than 4 hours needs medical help right away. Untreated priapism (a painful erection lasting more than 6 hours) can damage penile tissue and cause permanent loss of erections.
• Sudden loss of vision in one or both eyes means stopping Viagra and getting care. It may be NAION (non-arteritic anterior ischemic optic neuropathy, a loss of blood flow to the optic nerve). NAION occurs in 2.5 to 11.8 per 100,000 men aged 50 and over each year. Observational studies found about twice the risk shortly after PDE5 inhibitor use, but the label says this does not show the drug causes it.
• A sudden drop in or loss of hearing, sometimes with ringing or dizziness, also means stopping the drug and getting prompt care.

If you take a blood thinner and want to try Viagra

Tell the prescriber every medicine you take, including the blood thinner, any nitrate you keep on hand for chest pain, and any blood pressure or prostate medicine. Mention any bleeding disorder or stomach ulcer, since the label has no safety data for either. Ask the clinician who manages your anticoagulant whether anything about your condition changes the answer. Do not change your blood thinner dose to make room for an ED drug.

If you are deciding between sildenafil and tadalafil, how daily tadalafil compares with as-needed sildenafil covers timing and dosing differences.

Common questions

Can I take Viagra with aspirin?

The label reports that Viagra had no effect on bleeding time when taken with aspirin, and 50 mg of Viagra did not add to aspirin's effect on bleeding time (VIAGRA label, 2026). That study does not cover people taking aspirin together with an anticoagulant, so ask your prescriber if you take both.

Does Viagra make nosebleeds more likely?

Nosebleeds are on the label's list of postmarketing reports, but voluntary reports cannot show a rate or prove the drug caused them (VIAGRA label, 2026). If you take a blood thinner and get nosebleeds after taking Viagra, tell the clinician who manages your anticoagulant.

What if I get chest pain after taking Viagra?

The Viagra patient information says to stop sexual activity and get medical help right away if you have chest pain, dizziness, or nausea during sex (VIAGRA label, 2026). Nitrates are used to treat chest pain and must not be combined with Viagra, so make sure the people treating you know you took it and when.

Bottom line

You can take Viagra while on a blood thinner if your prescriber agrees; the label does not forbid the combination. What it forbids is taking Viagra with nitrates or riociguat. The label also has no safety data in people with bleeding disorders or active ulcers, and no studies with newer anticoagulants such as apixaban or rivaroxaban, so the decision belongs with the clinician who knows your full medication list. AlphaMD offers Viagra and Cialis for ED.