Some prescription medicines are controlled - meaning they have additional legal controls under the 'Misuse of Drugs legislation'. These medicines are usually called controlled medicines or controlled drugs (CD's). For example, a strong painkiller such as morphine is classed as a controlled drug.
As extra safety measures are needed to make sure these are prescribed and supplied safely, a signature will always be required on delivery for a controlled medicine.
If you are unsure whether your medicine is classed as a controlled drug, you can find a list here.