In the last few weeks, three different men asked me some version of the same question. Each of them had been taught to use injection therapy at home. Each of them was doing well with it. And each of them, almost in passing, asked: "How long is too long?"
It is a good question, and it deserves a clear answer. Here it is: if your erection is still firm four hours after you injected, it is an emergency. Go to A&E.
Injection therapy — an injection into the side of the penis that produces an erection — works well for many men when tablets have not. You were taught how to use it after a consultation, and you were probably told about prolonged erections at the time. But that conversation happened in a clinic, in daylight, with a lot of other information. The moment you actually need it may be at two in the morning, alone, and embarrassed.
So this page is for that moment. I want you to know what an erection that will not go down means, why the clock matters so much, what to say when you get to hospital, and how to lower the chance of it happening at all.
Most men who use injections never have this problem. I am not writing this to frighten you away from a treatment that works. I am writing it because this is one of the few situations in my specialty where a few hours genuinely change the outcome — and the men who do well are the ones who acted early.
The one number to remember — four hours
A normal erection from an injection lasts long enough for sex and then fades. An erection that lasts well beyond that, without going down, is called priapism.
The type of priapism that injection therapy can cause is called ischaemic priapism. Blood flows into the penis but cannot flow out. The trapped blood slowly runs out of oxygen, and the erectile tissue starts to suffer. It often becomes painful — but pain is not a reliable guide to how serious it is.
European urology guidelines treat an erection lasting more than four hours as an emergency. Treatment should start as early as possible — ideally within four to six hours. That is why the rule is so simple: