Omega-3 for dogs: benefits, sources and how to choose the right one

Omega-3 for dogs, and in particular marine EPA and DHA, are the most studied nutrients for joint comfort. Several controlled trials in dogs with arthritis have shown improved weight bearing and mobility after 6 to 13 weeks of regular intake. Choosing well comes down to three things: a marine source, a clearly stated amount of EPA and DHA, and a fresh product that is well protected from oxidation.

Here’s what omega-3s do, what the studies say, where to get them, what amounts have been studied and how to choose a fish oil or a diet that suits your dog.

What are omega-3s and why do dogs need them?

Omega-3s are a family of polyunsaturated fatty acids. Three of them matter for dogs:

Omega-3s are built into the membranes of every cell. When a dog gets more of them, EPA and DHA partly replace arachidonic acid, an omega-6 from which the body makes inflammatory mediators. The mediators made from EPA and DHA are less active, and some help inflammation to resolve. This mechanism explains why omega-3s are of interest for the joints, and also for the skin, coat, heart and kidneys.

Modern diets, rich in cereals and fats from land animals, provide plenty of omega-6 and relatively little marine omega-3. A targeted intake of EPA and DHA restores the balance.

Omega-3 for dogs with arthritis: what the studies say

Marine omega-3s are the best-documented nutritional ingredient for dogs with arthritis. The international COAST guidelines (2023) recommend prioritising them among nutraceuticals and suggest an enriched joint diet or an EPA and DHA supplement from the early stages of arthritis.

The measured effects remain moderate and appear gradually, which is why omega-3s are used as part of a multimodal plan rather than on their own. Read more about this approach in our guide to arthritis in dogs and its treatment.

The best sources of omega-3 for dogs

Fish oil and salmon oil

Fish oil for dogs is the most common source. Oils from small fish (anchovy, sardine, mackerel) are often the most concentrated and the least exposed to contaminants, because these species are short-lived. Salmon oil for dogs is very palatable and well accepted, but its EPA and DHA content varies widely from one product to another. Either way, the label has the final word.

Krill, green-lipped mussel and algae

• Krill oil: rich in EPA and DHA in phospholipid form, with a natural antioxidant, astaxanthin. It’s more expensive and often less concentrated per capsule.
• Green-lipped mussel (Perna canaliculus): it provides particular omega-3s (including ETA) and glycosaminoglycans. We’ve written a full article on green lipped mussel for dogs.
• Algae oil: a plant-based marine source, mainly rich in DHA, useful for dogs that are allergic to fish.

Diet

The ‘joint’ diets sold by vets are enriched with EPA and DHA. In the EU, and in the UK where the same rules were kept in UK law, a dietetic feed that claims to support the metabolism of joints in the case of osteoarthritis must meet minimum levels of omega-3 and EPA set by Regulation (EU) 2020/354, and its label must recommend seeking a vet’s advice. It’s a simple way to provide substantial amounts of omega-3 without adding anything to the bowl.

A little sardine canned in water with no added salt, or cooked salmon without bones or seasoning, can top up the diet now and then, but it won’t give a regular, measurable amount of EPA and DHA. Remember to count these extras as part of the daily allowance to protect your dog’s weight and joints: see our guide for the overweight dog.

Omega-3 dosage for dogs: what amounts have been studied?

The useful amount is calculated as EPA + DHA, never as ‘fish oil’ or ‘total omega-3’. What follows summarises the published reference points, for information only: the right amount for your dog should be decided with your vet, especially if it has other health problems.

• The COAST guidelines cite 75 to 100 mg of combined EPA and DHA per kilo of body weight per day as a starting intake for dogs with arthritis.
• In the Mehler et al. (2016) trial, dogs received an average of 69 mg of EPA and DHA per kilo of body weight per day.
• For arthritis, the US National Research Council (NRC) suggests a maximum intake calculated on metabolic body weight (310 mg multiplied by body weight in kilos to the power of 0.75), with a slightly higher safe upper limit (370 mg per kilo to the power of 0.75). Colorado State University’s veterinary hospital publishes a chart for vets.

Colorado State University’s veterinary service advises starting with about a quarter of the target amount and increasing gradually while keeping an eye on the stools. Mix the oil into a meal, never on an empty stomach.

How to choose fish oil for dogs

1. The amounts of EPA and DHA are stated per dose or per capsule. Without these figures, you can’t compare products.
2. The source is marine: fish, krill, green-lipped mussel or algae. Linseed oil on its own isn’t enough.
3. An antioxidant has been added, usually vitamin E (tocopherols). Omega-3s oxidise quickly, and an oxidised oil loses its value.
4. The packaging protects the oil: opaque bottle, pump or capsules, a best-before date and a batch number.
5. The manufacturer tests for purity (heavy metals, PCBs, dioxins, oxidation) and can provide a certificate of analysis.
6. The product is made for dogs: no lemon flavouring, sweeteners or garlic, which are sometimes found in products for humans.
7. The smell is fresh: if the oil smells rancid or very strong when you open it, throw the bottle away.

Store the oil somewhere cool with the cap tightly closed, and use it within a few weeks of opening. To compare omega-3s with other joint ingredients (glucosamine, collagen, turmeric), see our guide to choosing joint supplements for dogs.

Precautions and possible side effects

Omega-3s are well tolerated in published trials. Even so, the review by Lenox and Bauer (2013) lists the points to watch:

• Digestive upsets: loose stools, diarrhoea, vomiting, fishy breath. Introducing them gradually reduces these.
• Calories: oil provides about 9 kcal per gram. In an overweight dog, this needs to be factored into the diet.
• Clotting and wound healing: at high doses, omega-3s can alter how platelets work. Let your vet know before any surgery.
• Pancreatitis, diabetes, clotting disorders: ask your vet’s advice before starting.
• Interactions: mention any supplement if your dog is on long-term medication.

Fitting omega-3s into an overall joint plan

Omega-3s work best when they’re added to the other parts of a care plan:

1. A diagnosis and regular vet check-ups, with pain relief if your dog needs it.
2. A healthy weight, the most powerful way to reduce the load on the joints.
3. Regular, gentle activity, topped up with exercises for dogs with arthritis.
4. A balanced diet, enriched with EPA and DHA through food or a supplement.
5. Complementary ingredients, given every day for at least 6 to 8 weeks before judging.

To judge progress objectively, note three reference situations before you start (getting up in the morning, jumping into the car, how long a walk lasts before your dog tires), film your dog every two weeks and review things with your vet after two to three months.

Find more advice on what to put in your dog’s bowl in our dog nutrition section.

Key points on omega-3 for dogs

The marine omega-3s EPA and DHA are the best-studied nutritional support for dogs’ joints, with several favourable controlled trials and a meta-analysis. Choose a marine source, work out how much EPA and DHA you’re actually giving, opt for a fresh, tested product and give it every day for at least two months. Combined with a healthy weight, suitable exercise and regular check-ups with your vet, they support your dog’s comfort over the long term.