The legal status for supply of a medicinal product is a condition of the marketing authorisation. The categories for supply of a medicine are detailed below.

Subject to prescription:
- Non-renewable: dispensed once by the pharmacist unless the doctor directs otherwise
- Renewable: dispensed for up to six months by the pharmacist unless the doctor directs otherwise

Not subject to prescription:
- Pharmacy-only: available under the supervision of a pharmacist
- General sale: can, with reasonable safety, be sold without the supervision of a pharmacist

The IMB is responsible for deciding the legal supply category for a medicine. The supply category is specific to the product and is part of the marketing authorisation.

The criteria for deciding legal supply status are included in national legislation, Medicinal Products (Control of Placing on the Market) Regulations 2007, as amended. Generally new medicines may only be supplied on prescription. After use of the medicine for a number of years, sufficient information may be available to justify a change in the legal supply category to supply by a pharmacist without a prescription. It may also be possible for medicines previously supplied only by a pharmacist to be supplied on general sale, if appropriate.

Companies which hold marketing authorisations can apply to the IMB to have the supply categories changed. These applications are called ‘switching’ applications. Since the 2007 Regulations came into force, for nationally authorised products this requires an application to the IMB and no additional change to the Medicinal Products (Prescription and Control of Supply) Regulations is needed.

Switching applications are assessed by the IMB and its experts and if approved, a change to the condition of the marketing authorisation is made. Pharmacists and doctors are notified by the IMB of the change.