Chemical castration is being considered as a mandatory procedure for sex offenders as a way of reducing reoffending.
The procedure would be introduced as part of plans to overhaul the prisons system and tackle prison overcrowding.
The former Justice Secretary David Gauke has recommended the reforms as part of the overhaul, telling Sky News, “This is about reducing the risk of reoffending in future. There are some sex offenders who want to reduce their desires and if we can explore this, I think that is something that’s worthwhile.”
Gauke is currently leading an independent sentencing review.
Justice Secretary Shabana Mahmood is now mooting mandatory chemical castration, with pilots taking place in south-west England and plans for roll-out in 20 prisons across the country.
Under the scheme, prisoners could be released early for good behaviour and be supervised on licence, while short sentences of less than a year could be scrapped altogether. If passed, participation would be voluntary in England and Wales. As it stands, sexual offences account for 21 per cent of adults serving immediate custodial sentences, as recent of March 2025.
But what is chemical castration? How does it work and is it being used in other countries?
What is chemical castration?
Chemical castration involves using drugs to lower the production of hormones and androgens (male sex hormones) in a man’s testicles.
The hope is that chemical castration would suppress the sexual behaviours of sex offenders so that they can be safely released back into society without carrying a risk of reoffending.
Chemical castration has been previously used to treat those suffering with prostate cancer.
In contrast with surgical castration, chemical castration is administered via oral medication, injections, or an under-the-skin implant. The effects last for as long as you are taking the drugs. In other words, its impact is reversible.
How does it work?
There are different types of drugs used for chemical castration. The first category is GnRH agonists. These drugs stop your pituitary gland from releasing luteinizing hormone (LH). LH is the hormone which tells the testicles to produce testosterone.
GnRH works by stimulating LH which is why GnRH agonists can cause an initial flare in testosterone. However, the body soon ignores this and stops production of LH, reducing testosterone to very low levels.
The second category is GnRH antagonists which prevent testosterone production, without causing a testosterone flare. They work by directly inhibiting the pituitary GnRH receptors, leading to a suppression of testosterone production.
Finally, there are antiandrogen treatments, which work by stopping the body from using androgens, the male sex hormones.
The recommendations made by Gauke would propose using antiandrogen treatments, as well as SSRIs (selective serotonin-reuptake inhibitors) which are said to limit invasive sexual thoughts.
What are the risks of using chemical castration for sex offenders?
Whilst chemical castration can reduce libido, its other side effects include fatigue, shrinkage of testicles and penis, growth of breast tissue, and hot flushes. Over the long term, it can also lead to osteoporosis, depression, anaemia, and impaired glucose.
It is still up for debate whether lowering one’s sex drive is enough to prevent sexually violent offenses, as not every person will lose sexual function.
The drug also relies on long-term compliance, which is another concern of the scheme.
Are other countries using chemical castration?
Across the world, chemical castration has been used as a mandatory penalty or alternative to imprisonment for sex offenders.
Countries that punish rapists through castration include South Korea, Pakistan, the Czech Republic, and Ukraine. This includes countries that allow surgical castration.
In the US, six states – California, Florida, Iowa, Louisiana, Montana, and Wisconsin – and one territory, Guam, have legalised chemical castration as means of early release or as a condition of sentencing.
