In total, scientists in Great Britain conducted a total of 2.54 million procedures using living animals in 2025. The Home Office measures the quantity of procedures, rather than the number of animals used.
These figures only include procedures using ‘protected animals,’ which are animals that are regulated under the Animals (Scientific Procedures) 1986 Act. As a result, we do not know the total number of animals subject to scientific experiments in British laboratories.
The law allows UK scientists to use any species of non-human animals in medical research, although use of certain species is regulated. Mice, fish, rats, and birds are currently the most frequently used animals in British laboratory experiments. In total:
- Mice were used in 1.42 million procedures (56%)
- Fish were used in 406,400 procedures (16%)
- Rats were used in 228,600 procedures (9%)
- Birds were used in 254,00 procedures (10%)
Altogether, these species accounted for 91% of all recorded procedures in 2025. Other commonly used animals include sheep, rabbits, frogs, and guinea pigs.
Some animals have special protections by law to minimise their use. This group includes cats, dogs, horses, and non-human primates. Some of the numbers relating to specially protected animals actually increased in 2025:
- The number of non-human primates being used in scientific procedures for the first time has increased from 1,478 in 2024 to 1,845 in 2025.
- The number of dogs being used in scientific procedures for the first time has increased from 1,651 in 2024 to 1,706 in 2025.
- And the number of experimental procedures using cats has increased by 11% from 2024.
Animals of these species were used in 14,633 procedures (1.3% of all procedures) in 2025.
Since not all animal species come under UK regulation, not every type of animal used in British laboratories is named here. For example, experiments on non-vertebrates and non-cephalopods, such as insects, molluscs, and crustaceans, are not included.
Animals are used for a range of purposes in British research institutions. UK law regulates two broad types of scientific experiments using animals: procedures to create and breed genetically altered animals, and experimental procedures.
Animals can be bred to produce genetically altered offspring for use in experimental procedures. Typically, scientists modify the DNA of an animal to understand the role of genes in health and disease. Then, they will breed the genetically modified animals so the offspring can be used in scientific studies.
In 2025, 1.21 million procedures to produce genetically modified animals took place in British laboratories, accounting for 48% of the year’s procedures.
The majority of animals used in medical research are used for science experiments. In 2025, 1.32 million experimental procedures using animals took place in Great Britain, accounting for 54% of all procedures. Of these:
- 52% were for basic research, which expands our knowledge of the structure, functioning and behaviour of living organisms
- 26% were for applied or translational research, which addresses diseases through prevention and treatment development
- 19% were for regulatory research, which ensures that substances such as pharmaceuticals are safe and up to specification
- 2% were for other types of research, such as the protection of the environment, preservation of species, and higher education or training
For each research type, scientists use animals in experiments for different purposes.
- Within basic research, animals were mostly used to study the nervous system (24%), immune system (20%) and cancer (14%)
- Within applied research, animals were mostly used in experiments looking at animal diseases and disorders (35%), human cancer (23%) and and human infectious diseases (13%)
- Within regulatory research, animals were mostly used for toxicity and safety testing (55%)Understanding where and how animals are used in research is essential for identifying opportunities to replace animal experiments with effective non-animal approaches.
Understanding where and how animals are used in research is essential for identifying opportunities to replace animal experiments with effective non-animal approaches.
Animal experiments are classified by severity level. This is based on the likelihood of the procedure causing pain, suffering, distress, or lasting harm. There are five categories for the severity of a scientific procedure on an animal: sub-threshold, non-recovery, mild, moderate, and severe.
It is not just living animals that are used in medical research. Medical research commonly involves the use of animal-derived products for cell and tissue culture, and in the making of therapeutics.
The Home Office does not publish figures regarding animals used to make products for medical research. However, global usage and demand for these products indicates millions of animals are used for this purpose every year. Common examples of animal-derived products in medical research include:
- Foetal calf serum – production of this growth supplement kills around 2 million cow foetuses every year
- Matrigel – scientists develop this protein matrix, used to culture cells, by giving tumours to hundreds of thousands of mice a year
- Antibodies – these are harvested from tens of thousands of animals each year in the UK
At The Humane Research Trust, we support the use of
alternatives to animal research. Our funding helps scientists across the UK to replace live animal experiments and animal-based products in research. Our hope is a future where animals do not undergo experimentation to advance human health.
