en English

Testosterone is considered as a Class C, Schedule 4 Part2 controlled drug because it is in the same class as anabolic steroids which have been open to abuse because of their body enhancing properties.

There has historically been some concern by pharmacists that they are not allowed to dispense controlled drugs against an EU prescription, however the British National Formulary (BNF) gives very clear guidance on prescribing and dispensing laws in the UK and it advises:

Schedule 4 Part II includes androgenic and anabolic steroids, clenbuterol, chorionic gonadotrophin (HCG), non-human chorionic gonadotrophin, somatotropin, somatrem, and somatropin. Controlled drug prescription requirements do not apply and Schedule 4 Controlled Drugs are not subject to safe custody requirements.

Testosterone used to achieve masculinisation in trans masculine people is a core part of the medication used for medical transition. Used in this context it is a safe and well evaluated aspect of gender-affirming care.