Who should not take ED medicines?
Anyone who uses nitrates — angina medicines such as glyceryl trinitrate sprays, tablets or patches — or amyl nitrite ("poppers"), and men for whom sex is inadvisable because of their heart. Taken with nitrates, sildenafil can cause "a sudden drop in your blood pressure that is hard to treat" (healthdirect), and the ban covers every PDE5 inhibitor, tadalafil included (healthdirect). Beyond that, the labels rule the medicines out for a short list of conditions:
| Condition | Viagra (sildenafil) | Cialis (tadalafil) |
|---|---|---|
| Nitrates, "poppers" or riociguat | Must not take | Must not take |
| Heart or blood-vessel disease that makes sex inadvisable | Must not take | Must not take |
| Heart attack | Not within the last 6 months | Not within the last 3 months |
| Stroke | Not within the last 6 months | Not within the last 6 months |
| Blood pressure below 90/50, or high blood pressure not under control | Must not take | Must not take |
| Unstable angina | Must not take | Must not take (also angina during sex) |
| Uncontrolled irregular heartbeat, or recent heart failure | Severe heart failure: must not take | Must not take |
| Severe liver disease | Must not take | Only after a careful weighing of benefit and risk |
| Lost vision in one eye from NAION | Must not take | Must not take |
| Retinitis pigmentosa (an inherited eye disease) | Must not take | Not listed |
Sources: sildenafil label and tadalafil label, section 4.3; Viagra and Cialis consumer medicine information (Australia).
The list for Viagra, explained: who should not take Viagra? Which medicines — not conditions — clash with ED tablets is on Viagra and Cialis with other medicines.
Can you take Viagra or Cialis if you have heart disease?
It depends on the condition: nitrates, and a heart that cannot cope with sex, rule them out; many other heart conditions do not. The labels' concern is sex itself: "there is a degree of cardiac risk associated with sexual activity" (sildenafil label). Men with coronary artery problems were in the sildenafil trials, and 69% of them reported better erections; in 144 men with stable angina on angina medicines other than nitrates, sildenafil made no clinically relevant difference to how long they could exercise before angina set in (sildenafil label). Tadalafil caused no significant change in heart rate in healthy men (tadalafil label). The most-asked questions: is Cialis safe for heart patients, and does it affect heart rate or heart-attack risk? and can you take Viagra after a heart attack or with heart medicines?
After a stent, the question is usually the medicines that come with it. healthdirect asks men to tell their doctor about every medicine, including "any sprays or tablets you use for chest pain", before asking for an ED medicine, and the Cialis leaflet asks you to tell emergency or ambulance staff that you take it if you are treated for a suspected heart problem (Cialis consumer medicine information). See can heart stent patients safely take Viagra?
An irregular heartbeat that is not under control rules tadalafil out, and atrial fibrillation is among the rare reactions reported with sildenafil (sildenafil and tadalafil labels); whether the rhythm problem can itself lead to ED is asked in can an irregular heartbeat (atrial fibrillation) lead to erectile dysfunction? It works the other way too: reduced blood flow from clogged arteries is one of the physical causes of ED (healthdirect) — can heart problems cause erectile dysfunction?
Can low iron, back pain or other conditions cause ED?
Many conditions can contribute to ED, but low iron and back pain are not on healthdirect's list. healthdirect names nerve problems such as spinal cord injury, Parkinson's disease and Alzheimer's disease; hormone problems including an underactive thyroid; hypogonadism, "where the testicles cannot make enough testosterone"; and, as chronic conditions that can contribute, high blood pressure, high cholesterol, cardiovascular disease, obesity and sleep disorders, besides alcohol, smoking and some medicines (healthdirect). The conditions people ask about:
- Low iron or anaemia is not on healthdirect's list. The one anaemia the ED medicine labels mention is sickle cell anaemia, which makes priapism more likely: can low iron or anaemia cause erectile dysfunction?
- Low back pain is not on it either, though spinal cord injury is; and back pain is one of tadalafil's most common side effects (tadalafil label): what links low back pain and erectile dysfunction?
- MS, a condition of the brain and spinal cord, is not named, though other nerve conditions are: can multiple sclerosis cause ED, and what is the best treatment?
- Sleep problems are on the list as "sleep disorders": can sleep apnoea cause ED, and can CPAP help?
- Thyroid and testosterone: an underactive thyroid and hypogonadism are both on it: does thyroid function affect testosterone levels? and what happens if a varicocele is left untreated?
- Constipation and kidney stones are not on it; what is known is in is there a link between constipation and ED? and can kidney stones cause impotence?
Can you take Viagra after a stroke?
Not in the first 6 months after one. The Australian Viagra and Cialis leaflets both rule them out for 6 months afterwards, and the sildenafil label lists it among the rare serious events reported with the medicine, mostly in men who already had cardiovascular risk factors (Viagra and Cialis consumer medicine information; sildenafil label). The question as people ask it: can stroke patients safely use Viagra?
Does diabetes cause ED, and do ED medicines work with it?
It can contribute to ED — and ED is often one of its first signs. healthdirect lists it among the chronic conditions behind ED and among the medical problems ED can be the first sign of. What is known about why: causes and effects of ED in men with diabetes.
ED medicines are used in diabetic men without a dose change. One man in five in the sildenafil trials was diabetic, and 59% of them reported better erections (sildenafil label); tadalafil needs no dose adjustment for diabetic men (tadalafil label). The Viagra leaflet asks diabetic men to mention it before starting, "especially if you also have eye problems" (Viagra consumer medicine information). Which medicine and what else is on offer: which ED medication is safe and effective for diabetic men? and the treatment options for ED with diabetes. Medicines for the condition itself are on our type 2 diabetes pages.
Can you take ED medicines with high blood pressure?
Yes, if it is under control — not if it is uncontrolled or very low. Sildenafil lowers blood pressure a little on its own, and blood-pressure medicines add to that; alpha-blockers call for a lower starting dose (sildenafil label). High blood pressure is itself one of the chronic conditions behind ED, and some of its medicines can cause it too (healthdirect). See what Viagra does to blood pressure in men with hypertension and can Viagra be taken with amlodipine and other blood-pressure medicines?
What about kidney or liver disease?
The dose changes; severe liver disease rules sildenafil out. With severe kidney disease or liver disease such as cirrhosis, sildenafil is cleared more slowly, so its label suggests starting at 25 mg (sildenafil label). Tadalafil is taken at 10 mg with kidney or liver disease, is capped at 10 mg with severe kidney disease, and is not taken daily then (Cialis consumer medicine information). Vardenafil is ruled out with severe liver disease and with end-stage kidney disease on dialysis (EMA). More in does Viagra affect kidney function? and can sildenafil affect the liver in liver disease or cirrhosis?
Can ED be the first sign of another health problem?
Often, yes. "Often, erectile dysfunction is the first sign of certain medical problems." Diabetes, cardiovascular disease, high blood pressure and high cholesterol are healthdirect's examples, which is why a doctor checks your general health, may order blood tests or an ultrasound, and "will first treat any underlying conditions that may be causing ED" (healthdirect). In Australia you need a prescription for any ED medicine, and it is your GP who weighs your conditions and chooses one (healthdirect). Whether software can help with that kind of assessment is a separate question: what are the benefits and risks of using AI in healthcare?
Sources
- healthdirect — Erectile dysfunction; healthdirect — Erectile dysfunction medicines; healthdirect — Sildenafil (Viagra) (all last reviewed February 2025)
- Viagra consumer medicine information (Australia, October 2024); Cialis consumer medicine information (Australia, October 2024)
- EMA — Viagra (sildenafil) product information, sections 4.2, 4.3, 4.4, 4.8 and 5.1; EMA — Cialis (tadalafil) product information, sections 4.2, 4.3, 4.8 and 5.1
- EMA — Levitra (vardenafil), medicine overview (updated 20 January 2025)
