Testing on animals

Scientific procedures involving animals are used in multiple research fields including medicine, veterinary science and regulatory safety testing. The Animals (Scientific Procedures) Act 1986 (ASPA) regulates when animals can be used and permits their use only if no viable non‑animal method can achieve the same scientific purpose. In 2025 the government set a long-term aim to eliminate animal testing in science by publishing Replacing animals in science: A strategy to support the development, validation and uptake of alternative methods.

Legislation and regulation

ASPA regulates any scientific or educational procedure on a protected animal that may cause pain, suffering, distress or lasting harm equivalent to or higher than that of inserting a hypodermic needle. This includes actions such as dosing, sampling, deliberate omission such as withholding food or water, and allowing the breeding of animals with harmful genetic traits. A protected animal is defined by ASPA as any living vertebrate (other than humans) and any living cephalopod, such as octopuses, squid, and cuttlefish. Other animals, such as insects, are not covered by the act. Home Office guidance also sets out when embryonic, foetal and larval forms of animals become protected.

Procedures are licensed and classified according to their anticipated impact. Categories include non‑recovery (where animals do not regain consciousness after anaesthesia) and mild, moderate or severe levels of expected suffering.

ASPA requires a harm–benefit assessment showing that expected benefits outweigh potential harms and that no suitable alternative exists. Additional protections apply to certain species, including cats, dogs, horses and non‑human primates. Project licences involving these species can be granted only where the work cannot be achieved using other species.

The 3Rs: Replacement, reduction and refinement

The principles of replacement, reduction and refinement (3Rs) are embedded in ASPA and related guidance.

• Replacement requires the use of scientifically satisfactory non‑animal methods, such as computer modelling, wherever possible.
• Reduction requires minimising the number of animals used without compromising research aims.
• Refinement requires improving care, housing and methods to reduce pain, suffering and distress.

The UK National Centre for the Replacement, Refinement and Reduction of Animals in Research promotes the application and development of these principles.

Regulatory bodies

The Animals in Science Regulation Unit (ASRU) in the Home Office administers and enforces ASPA in Great Britain. It provides regulatory advice, manages licences and inspects establishments to assess compliance. Northern Ireland’s Department of Health carries out equivalent duties. The Animals in Science Committee is an independent body advising the Home Office and the Northern Ireland Department of Health.

A triple licensing system applies to all regulated procedures. Researchers must hold a personal licence, the work must be authorised by a project licence and be carried out at a licensed establishment. ASRU inspectors assess project applications through a harm–benefit analysis and publish non‑technical summaries outlining objectives, predicted harms and 3Rs considerations.

The government’s position on animal research

The 2024 Labour Party manifesto (PDF) committed to working towards phasing out animal testing. In 2025 the government published a UK Life Sciences Sector Plan and a Replacing animals in science: A strategy to support the development, validation and uptake of alternative methods (‘the strategy’) setting out a long‑term aim to eliminate animal testing in science except in exceptional circumstances, while continuing to support regulated research where no alternatives exist. The strategy aims to accelerate the development and uptake of non‑animal methods, strengthen regulatory confidence and build infrastructure to support innovation.

Perspectives on animal research

Debate continues about the scientific and ethical justification for using animals in research. Supporters argue that past medical advances have relied on animal studies and that UK legislation minimises harm. Critics, however, question both the moral justification for causing suffering to animals and the scientific validity of results that may not always translate reliably to humans. Some discussions focus on how rapidly non‑animal methods can be adopted while maintaining scientific standards.

Animal experiment statistics

Home Office data shows that In 2024, there were 2.6 million completed procedures involving living animals in Great Britain. This was a decrease of 1% compared to 2023 and the lowest number since 2001.

Source: Home Office, Statistics of scientific procedures on living animals, Great Britain: 2024 (and earlier versions)

2.6 million animals were used for the first time in scientific procedures in 2024. This was down by 37% on the recent peak of 4.1 million in 2015.

73% of the animals used in these procedures were mice. The next most often used animals were Zebrafish (12%), rats (6%) and chickens (4%).

Cats, dogs, horses and non-human primates are subject to additional protection under the Animals (Scientific Procedures) Act 1986. In 2024 there were 16,147 scientific procedures carried out on specially protected species. This figure was 7% fewer than in 2023 and 12% below the recent peak in 2018.

Source: Home Office, Statistics of scientific procedures on living animals, Great Britain: 2024

A total of 3,224 animals from specially protected species were used for the first time in these procedures. There were:

• 1,651 dogs (96% of which were Beagles)
• 1,478 primates (91% of which were Cynomolgus monkeys)
• 60 horses
• 35 cats