How we compare medicine prices
Last updated 21 September 2026
The short version. The list of medicines is the Veterinary Medicines Directorate’s own. The retailers are the ones the VMD accredits. We read the price each retailer publishes, show the date we read it, and link to the page it came from. Some of those links may pay us a commission. That never changes who is listed or the order they appear in.
Which medicines are listed
Every medicine on this site comes from the VMD’s Product Information Database, which is the register of what is authorised for sale in the UK. We use the authorised name, the active substance, the strength, the form and the legal category exactly as the register has them. We add nothing of our own. When a product is suspended or its authorisation expires, it stops being shown here.
A page for one kind of medicine lists every authorised product with that active substance, strength and form, in alphabetical order, in one format, whether or not anyone has a price for it. No product is featured, badged, recommended or called a better buy.
The index can be narrowed by type of medicine, such as wormers or heart medicines. A medicine’s type comes from the therapeutic group the VMD’s register gives it, put into plain words. A type says what a medicine is. It never says what a medicine is for, and choosing one only narrows the same alphabetical list.
Which retailers are listed
Only retailers on the VMD’s Accredited Internet Retailer Scheme list, and only for the legal categories the VMD accredits them to sell. A retailer accredited to sell one category is not shown against a medicine in another. A medicine on general sale needs no accreditation, so any retailer on the list may be shown for it. We read that list regularly. A retailer that leaves it stops being shown.
Every accredited retailer we can read is listed, whether it pays us or not. We do not take payment for inclusion, for position, or for being shown at all.
How the prices are read
A program reads the price each retailer publishes on its own website. It obeys each site’s robots.txt and its stated crawl delay, and identifies itself. It reads the price, the pack size and whether the item is in stock. It never reads a figure a retailer does not show the public. Where a retailer supplies a product feed instead, we read the feed.
Matching a retailer’s listing to the right authorised product and pack is done by rule: the brand, then the form, then the strength, then the pack size, and the product’s own document number where the retailer gives one. A second, independent check reads each match and flags any it doubts. A person then approves the listing before its price is shown. A pack size is never guessed. A listing we cannot place is not shown.
A person approves listings one at a time, or one retailer’s listings together after reading them. Where the rules leave a listing open, an AI model may prepare a recommendation for that person to read: which authorised product it is, and which pack. A recommendation can only name a product the rules themselves put forward. Nothing is approved until the person reading it says so.
That approval is carried forward in four cases. The same barcode appears at another retailer. The same retailer lists the same words and the same pack at a new address. The retailer rewords a listing and it still names the same product and pack. A page a person has approved gains a new pack size, the size is stated and the check does not doubt it. A page we have not read before always waits for a person. We keep a record of every price shown this way and can take it back.
Each price carries the date it was read. If a price is older than the page says, tell us and we will read it again.
Delivery, and what a total means
Most retailers do not publish a delivery cost on the product page. Where one does, we show it and the total, and order the retailers for that pack by that total. Where one does not, the row says not known, the pack says we do not have every retailer’s delivery cost, and the retailers are ordered by the price of the medicine alone. We do not estimate postage and we do not present a total we cannot stand behind.
Retailers are only ever ordered within one pack of one product. Products are never ordered by price and nothing on this site is marked cheapest or best.
The prescription
A prescription from your vet is needed for a POM-V medicine. Which medicine is prescribed is your vet’s decision alone, and nothing on this site is advice about what to give an animal. Your practice may charge to write the prescription. Where that practice publishes its fee we show its own figure. Where it does not, we use the cap in the Veterinary Services Market Investigation Order: £21 for a written prescription, and £12.50 for each further item on the same prescription. Those figures come from the same place as the practice prices on the rest of this site, which are explained in how we collect vet prices.
Which links pay us
A link marked “Paid link” pays us a commission if you buy through it. That link goes through an affiliate network’s tracking address before it reaches the retailer. A commission never changes which retailers are listed, which products are listed, or the order anything appears in. The code that orders the rows does not know which links pay.
Correcting a price
If a price here is wrong, out of date, or against the wrong product, write to [email protected] with the page address and we will read it again. A retailer that wants to be removed can say so at the same address, and we will remove it.