Quick answer: omega-3 fish oil has the best research behind it of any joint supplement for dogs with arthritis, but only at a meaningful dose of EPA and DHA, and most joint chews and capsules contain far too little to get there. In the UK, plain salmon body oils that publish their EPA and DHA content, such as Pooch & Mutt Salmon Oil and Wilsons Premium Scottish Salmon Oil, are the most practical and affordable way to reach the doses used in studies: roughly £5 to £12 a month for a 25kg dog. Ask your vet to set the dose, especially if your dog is on a joint diet, NSAIDs or due for surgery.
Transparency note: MedPaw makes a joint chew, not a fish oil, so we don't sell anything on this list. Product figures were checked against manufacturer and retailer listings in October 2026. This guide isn't a substitute for advice from your vet.
Why omega-3 matters for dogs' joints
EPA and DHA, the omega-3 fatty acids found in oily fish, help reduce the inflammation involved in arthritis. A 2022 systematic review and meta-analysis of 72 trials (Barbeau-Grégoire and colleagues) found omega-3s had the strongest and most consistent evidence for easing arthritis pain in dogs; only 2 of 20 omega-3 trials found no effect. By contrast, it found no pain-relieving effect for glucosamine and chondroitin.
It's also why many vets recommend prescription joint diets such as Hill's j/d, Purina Pro Plan Veterinary Diets JM and Royal Canin Mobility Support, which are enriched with omega-3s.
How much omega-3 does a dog need for its joints?
What matters is the combined amount of EPA + DHA, not "fish oil" or "omega-3" on the front of the pack. Research gives a rough guide:
- A 2016 double-blind trial in 74 dogs with osteoarthritis (Mehler and colleagues) found improvements at about 69mg of EPA + DHA per kg of bodyweight per day.
- Published therapeutic ranges for dogs run from about 50 to 220mg per kg per day, with the higher end used for arthritis.
- The US National Research Council's safe upper limit works out at about 4,100mg a day for a 25kg dog.
So a 25kg dog might typically be given around 1,700 to 2,500mg of EPA + DHA a day. That's a lot more than most people expect, and far more than joint chews provide. Your vet should set the exact dose, because omega-3s from a joint diet count towards the total, and higher doses need more care. Our omega-3 dosage guide explains the maths in more detail.
Why most joint products can't reach a useful omega-3 dose
| Source | EPA + DHA per unit | Units for about 2,000mg a day |
|---|---|---|
| Scottish salmon oil (EPA 7 to 9%, DHA 10 to 12%) | About 155 to 195mg per ml | About 10 to 13ml |
| Nordic Naturals Omega-3 Pet (US label) | About 239mg per ml | About 8ml |
| Lamberts / Nature's Best Omega 3s for Cats and Dogs | 165mg per capsule | About 12 capsules |
| Flexadin Advanced chew | 84mg omega-3 per chew (9.3mg EPA) | Not practical |
| Antinol Joint Care Pro | 15mg (10mg EPA, 5mg DHA) per capsule | Not practical |
Best fish oils for dogs' joints in the UK
Pooch & Mutt Salmon Oil
Scottish farmed salmon oil with published EPA (7 to 9%) and DHA (10 to 12%), which works out at roughly 155 to 195mg of EPA + DHA per ml. A 25kg dog would need around 9 to 16ml a day for 70 to 100mg per kg. The 500ml bottle is £11.49 on Pooch & Mutt's site (often on offer) and around £14 to £15 elsewhere, so roughly £6 to £12 a month for a 25kg dog. Pooch & Mutt's own label dose for large dogs lands in the same range.
Wilsons Premium Scottish Salmon Oil
Same EPA and DHA percentages as above, with a pump that gives 2ml per press. The 1-litre bottle (£16.99) makes it the cheapest per ml we found, at roughly £5 to £8 a month for a 25kg dog.
Nordic Naturals Omega-3 Pet
A more concentrated oil from anchovy, sardine, mackerel and herring, at about 239mg of EPA + DHA per ml on the US label, so a 25kg dog needs less: around 7 to 10ml a day. It's sold by some UK retailers, but we couldn't confirm the UK pack size and price, so compare cost per ml before buying.
Capsules (Lamberts / Nature's Best)
Lamberts and Nature's Best sell the same Omega 3s for Cats and Dogs capsule, with 99mg EPA and 66mg DHA per capsule. Good for small dogs or as a low-dose top-up, but a 25kg dog would need about 11 to 15 capsules a day to reach study doses. The label's own dose is far lower than that.
Prescription joint diets
Hill's j/d, Purina JM and Royal Canin Mobility Support build omega-3s into a complete food, which is the simplest option if your vet recommends one. Hill's publishes EPA (0.386%) and DHA (0.261%) for its dry j/d. Don't add a high-dose fish oil on top of a joint diet without your vet's input, as it's easy to overshoot.
Products we couldn't recommend for joint dosing
- Salmon oils that don't publish EPA and DHA, including some own-brand and budget bottles. Without the figures you can't dose them.
- Skin and coat blends mixed with flax or borage oil. They're designed for skin, not joint-level omega-3 doses.
- Cod liver oil at joint doses. It also contains vitamins A and D, which can build up to harmful levels. Use a fish body oil instead. See cod liver oil and fish oil for dogs.
- Green-lipped mussel oil products such as Antinol, if your aim is EPA and DHA. Any benefit they offer is claimed to come from other compounds, not omega-3 quantity. See Antinol vs green-lipped mussel.
How to give fish oil safely
- Agree a target with your vet. Bring the bottle so they can see the EPA and DHA figures.
- Build up slowly. Start with about a quarter of the target and increase over two to three weeks to avoid loose stools.
- Count the calories. Oil has about 8 calories per ml, so 12ml a day adds around 100 calories. Trim your dog's food slightly to stop weight gain, which would undo the benefit.
- Keep it fresh. Store it cool and dark with the lid on, use it within the time on the label once opened, and bin it if it smells rancid.
- Tell your vet before any surgery, as high doses can affect blood clotting, and if your dog has had pancreatitis or is on NSAIDs.
- Give it 8 to 12 weeks. Omega-3 effects build gradually.
Fish oil alongside a joint supplement
Fish oil and a joint supplement do different jobs and are often used together. Many joint chews, including ours, contain little or no EPA and DHA. MedPaw Hip & Joint Chews contain flax seed, a plant source of omega-3 (ALA) that dogs convert poorly into EPA and DHA, so if your vet recommends omega-3s, add a marine oil alongside. Compare joint supplements in our guide to the best joint supplements for dogs in the UK.
If your dog is in pain, fish oil isn't a substitute for proper pain relief. See what you can safely give a dog for joint pain.
What is the best fish oil for dogs' joints in the UK?
A plain fish body oil that publishes its EPA and DHA content, such as Pooch & Mutt Salmon Oil or Wilsons Premium Scottish Salmon Oil, lets you reach study doses affordably. Nordic Naturals is more concentrated. Avoid cod liver oil at joint doses.
How much fish oil should I give my dog for arthritis?
Studies have used roughly 50 to 100mg or more of combined EPA and DHA per kg of bodyweight a day, which is around 1,700 to 2,500mg for a 25kg dog. Ask your vet to set the dose, especially if your dog eats a joint diet or takes other medication.
Is salmon oil or fish oil better for dogs' joints?
What matters is the EPA and DHA content, not the fish. Scottish salmon oils typically contain around 155 to 195mg of EPA and DHA per ml. Concentrated anchovy and sardine oils can be higher.
Can I give my dog cod liver oil for joints?
Not at joint-support doses. Cod liver oil also contains vitamins A and D, which can reach harmful levels if you give enough to get a useful amount of omega-3. Use a fish body oil such as salmon oil instead.
How long does fish oil take to work for dog arthritis?
Usually several weeks. Give it at least 8 to 12 weeks at a consistent dose before judging, and keep a weekly note of your dog's mobility.
Can fish oil upset my dog's stomach?
Yes, loose stools and fishy breath are the most common side effects. Build up slowly over two to three weeks, and give it with food.
