How we rank

We convert everything to your pet

A label says “500 mg green-lipped mussel per serving”. That tells you nothing about whether your 30 kg dog gets enough of it. We take the manufacturer's dosage for your pet's weight, work out the amount of each ingredient per kilogram per day, and compare it with reference doses from the literature. Every ingredient lands somewhere between “traces” and “enough”.

The same figure appears on every product page, where you can change the weight and watch the dose move.

Evidence counts

An ingredient dosed high enough, with good studies behind it, counts for more than a herb used traditionally with nothing to show. Several ingredients in trace amounts do not add up to a good product, and we deduct points for it. Each ingredient's evidence is written on its own page, with sources and the reason for its grade.

We grade on studies in dogs and cats, not in people, and separately for each species, because the studies are separate too:

• Well supported: several randomised controlled trials in that species with consistent results, or a systematic review that finds an effect.
• Some evidence: at least one randomised controlled trial shows an effect, but it has not been repeated, is small, or is contradicted by others.
• Traditional use: long in use and with a plausible mechanism, but supported only by studies without a control group.
• No evidence: controlled trials found no effect, a systematic review advises against it, or there are no data.

A grade can change, in either direction. We had biotin as "some evidence" until we found that the only study on skin and coat had no control group.

How we rank

The order comes from four quantities, weighted like this:

• The main concern accounts for the whole score. Every ingredient that matches it counts by its dose relative to the reference, multiplied by its evidence: strong 0.85, moderate 0.6, traditional use 0.3, no evidence 0.
• A second concern, if you named one, counts half as much as the first.
• Your preferences (made in the EU, a matching seal) add 5 per cent each, 10 at most.
• Trace amounts cost points: 3 per cent off for each ingredient below 15 per cent of the reference, 15 at most.

Where a manufacturer names an ingredient but not its amount, it counts as half a dose, and all such ingredients together can supply at most half of a concern's score. Otherwise a powder listing eight unquantified herbs would outrank a product whose dose can be checked.

The percentage shown is the score relative to the best score possible for your exact answers. Products on the same score are ordered by cost per day. Commission enters none of these quantities.

Sometimes the answer is nothing

If you feed a complete food and have no specific concern, you usually do not need a supplement, and we will say so. With a diagnosed condition or ongoing medication we show no product list at all, only questions to take to your vet. Supplements are food, not medicine, and we do not phrase it otherwise anywhere on this site.

Prices and check dates

Prices come from retailer data and carry the date they were fetched. Every product shows when we last checked its label figures. Anything imported from a feed stays hidden until a person has looked at it. Each night we also check that every shop link still works.

How we make money

From links to shops. Some shops pay us a commission and some do not, and both sit side by side on every product. The part of our software that scores and sorts products never sees the commission at all: it knows only species, weight, ingredient amounts, dosage, price and availability. An automated test checks that this stays true with every change.

None of it changes the price you pay.