Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Get emergency help if:
an erection lasts longer than four hours
you have chest pain, severe breathlessness, or feel faint during sexual activity
the penis is injured with a sudden pop, severe pain, swelling, or rapid bruising
If chest pain occurs after taking a PDE5 inhibitor, tell emergency staff what you took and when.
Do not take nitrate medicine unless emergency professionals who know about the PDE5 inhibitor direct you to do so.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek urgent medical advice if you develop sudden vision loss or sudden hearing loss after taking an erection medicine.
3
Does any of this apply?
Book an appointment
Arrange a routine appointment if erection problems keep happening, cause distress, or have changed noticeably.
Assessment is also useful if you have diabetes, heart or circulation problems, reduced sexual desire, penile pain, a new curve, or symptoms of low testosterone.
Every sign above is quoted from the sofidex article on Erection problems. If you are not sure, err upward — it is always reasonable to be checked.