The concept of self-poisoning could be legitimately applied in a deeply religious Christian context and, at the same time, be justified from the Greek–Arabic medical tradition. In more recent centuries, there have been a number of celebrated instances of investigators deliberately self-poisoning, but on these occasions simply in order to see what would happen. For instance, John Hunter in 1767 inoculated himself with the poison – the virus – of gonorrhoea in an attempt to prove that gonorrhoea and syphilis were the same disease. Ole Grell takes us on an unexpected journey to the heart of the Protestant Reformation, showing how Martin Luther, himself a former friar and therefore sworn to celibacy, promoted the view that sexual abstinence – that is, the unnatural retention of semen, both male and female – was itself a form of self-poisoning. Its antidote, Luther claimed, was marriage. As Grell shows, this position could find support in classical medical texts by Galen, one of which may have been Luther’s source.