About this guide
This guide explains how rat poison (rodenticide) works in the UK, the difference between first-generation and second-generation anticoagulant products, the CRRU regulations that restrict professional use of the most potent products, resistance in Yorkshire rat populations, and safe use guidance. The page supports Apex Pest Control Ltd's rat control service by explaining the professional approach to rodenticide use before users choose a treatment provider.
Rat poison — more precisely called rodenticide — encompasses a range of products used to control rat populations. In the UK, the most commonly used professional rodenticides are anticoagulants: compounds that prevent blood clotting, causing internal haemorrhage. Understanding how these products work, what restrictions apply, and what makes professional use different from consumer DIY is important for anyone dealing with a rat infestation.
How anticoagulant rodenticides work
Anticoagulant rodenticides work by blocking the recycling of vitamin K in the body. Vitamin K is essential for the production of clotting factors; when it is depleted, blood loses the ability to clot, leading to internal bleeding. Death occurs over several days after a lethal dose has been consumed — this delay is deliberate, as it prevents rats from associating the bait with illness and avoiding it (bait aversion).
The delayed action also means that rodenticides do not provide immediate results. Activity at bait stations may remain unchanged or even increase in the first few days as rats that have not yet consumed a lethal dose continue feeding. The reduction in population is typically not apparent until 7–14 days after the initial bait placement.
Research by the Rodenticide Resistance Action Group found that approximately 74% of Yorkshire brown rat populations carry a VKORC1 gene mutation that confers resistance to first-generation anticoagulant rodenticides including warfarin — meaning FGARs are ineffective for the majority of rat populations in the region.
— Rodenticide Resistance Action Group (RRAG), 2022
First-generation anticoagulant rodenticides (FGARs)
First-generation anticoagulants (FGARs) — including warfarin and coumatetralyl — require rats to feed on the bait multiple times over several days to accumulate a lethal dose. They have a relatively short persistence in the food chain compared to SGARs, which reduces secondary poisoning risk to predators such as barn owls and kestrels that may consume poisoned rats.
FGARs are available in consumer products as well as professional formulations. However, their effectiveness in Yorkshire is severely compromised by widespread VKORC1 resistance. A professional pest controller aware of local resistance data will not default to warfarin in areas where resistance is established.
Second-generation anticoagulant rodenticides (SGARs)
Second-generation anticoagulants (SGARs) — brodifacoum, bromadiolone, difethialone, and difenacoum — are significantly more potent than FGARs. A lethal dose can be accumulated after a single large feed, and SGARs are effective against populations resistant to first-generation products. This potency comes with higher secondary poisoning risk: SGARs persist in the body tissue of poisoned rodents for longer, creating greater risk to predators and scavengers including barn owls, red kites, polecats, and stoats.
SGARs are licensed for professional use under the Biocidal Products Regulation (BPR PT14). Since January 2026, outdoor use of any SGAR by a professional pest controller requires:
Holding the RSPH Level 2 Award in Rodent Control (or equivalent recognised qualification) and registration with the Campaign for Responsible Rodenticide Use (CRRU) as a qualified operator. A pre-treatment property survey, documented justification for selecting an SGAR over an FGAR, and maintenance of treatment records that are available for inspection.
Bromethalin is not licensed for use in the UK or EU and must never be used or recommended. Mothballs and naphthalene are not licensed under the Biocidal Products Regulation as rodent control products in the UK — they are not effective rat deterrents and should not be suggested or used as part of any pest control programme.
Non-anticoagulant rodenticides
Alphachloralose is occasionally used for mice control in specific circumstances (typically indoors at low temperatures) but is not used for rats. Zinc phosphide is used in agricultural settings but is highly restricted. Carbon dioxide is used as a humane killing agent in some professional trapping programmes. These products are all professionally administered — they are not available as consumer products for rat control in the UK.
Rodenticide resistance in Yorkshire
The VKORC1 gene mutation — which reduces the binding affinity of vitamin K epoxide reductase for anticoagulants — has been identified in approximately 74% of Yorkshire brown rat populations sampled by RRAG. Rats carrying this mutation can consume and survive doses of warfarin and related FGARs that would kill a susceptible rat. This does not confer resistance to all SGARs, but it does mean that FGAR-based consumer products are often ineffective in Yorkshire without professional knowledge of local resistance prevalence and product selection.
Safe use and storage of rodenticide
All rodenticides must be used in tamper-resistant, lockable bait stations. Loose bait placement is prohibited under UK regulations for professional use and is unsafe in any context. Keep all rodenticide products in their original labelled packaging in a locked storage facility. Dispose of unused bait and empty packaging according to label instructions. Keep children and pets away from areas where bait stations are deployed. If accidental ingestion by a human or animal is suspected, contact the National Poisons Information Service (NPIS) or a veterinarian immediately.
Frequently Asked Questions
What is the most effective rat poison in the UK?
The most effective rodenticide depends on local resistance patterns. In Yorkshire, approximately 74% of brown rat populations carry VKORC1 resistance to first-generation anticoagulants like warfarin, making them ineffective in most of the region. Second-generation anticoagulants (SGARs) such as brodifacoum and bromadiolone are more potent and effective against resistant populations, but outdoor professional use now requires CRRU registration and a Level 2 qualification in rodent control (from January 2026).
How long does rat poison take to work?
Anticoagulant rodenticides take 4–7 days to cause mortality after a lethal dose has been consumed. This delay is intentional — it prevents rats from associating the bait with illness. The reduction in rat activity is typically not visible until 7–14 days after bait is first placed.
Is rat poison dangerous to pets and children?
Yes. Anticoagulant rodenticides are toxic to all mammals, including dogs, cats, and children. Bait must always be placed inside tamper-resistant, lockable bait stations. Pets and children should not have access to areas where bait stations are deployed. If accidental ingestion is suspected, contact the National Poisons Information Service (NPIS) at 0344 892 0111 or your veterinarian immediately.
Can I buy rat poison without a professional?
Consumer rodenticide products containing first-generation anticoagulants (FGARs) such as warfarin are available to the public in the UK. Second-generation anticoagulants (SGARs) are restricted to professional use. Note that in Yorkshire, where warfarin resistance is widespread, consumer FGAR products are often ineffective against the local rat population.
What is the CRRU UK Code and who does it affect?
CRRU (Campaign for Responsible Rodenticide Use) publishes the UK Rodenticide Stewardship Code, which governs professional use of anticoagulant rodenticides. From January 2026, pest controllers using SGARs outdoors must hold a recognised qualification (such as the RSPH Level 2 Award in Rodent Control) and register with CRRU. The code aims to reduce secondary poisoning of wildlife from anticoagulant use.
Are there any rat poisons that are not anticoagulants?
Yes, though their use is restricted. Alphachloralose is occasionally used for mice indoors in specific temperature conditions. Zinc phosphide is used in agriculture. Carbon dioxide is used professionally for humane killing in trapping programmes. These products are not available as consumer DIY products. Bromethalin is not licensed in the UK or EU and must not be used.
Do dead rats from poison cause a smell problem?
Yes. Rats that consume anticoagulant bait typically die away from the station, often in wall cavities, loft spaces, or beneath floorboards. Decomposition in inaccessible voids produces an unpleasant odour that may persist for 2–4 weeks depending on the cavity and ambient temperature. A professional pest controller will search for and remove accessible carcasses during monitoring visits.