Fish oil for dogs and cats: when omega-3s help and how to choose one

Fish oil is one of the few pet supplements with a reasonable body of research behind it. The veterinary nutritionists at Tufts University's Cummings School explain where omega-3 fatty acids can help, and why the dose matters more than the brand name.

What's in it

The useful parts are two omega-3 fatty acids, EPA and DHA. Both help reduce inflammation, and both are found in fish oil.

Where it can help

• Joint disease. Tufts notes that the right dose of omega-3s has been shown to ease some joint pain. Severe arthritis still needs medication, and getting an overweight dog to a trim weight can help even more.
• Heart disease. Omega-3s can reduce inflammation linked to heart failure, may help limit the muscle loss that comes with it, and there's evidence they help with abnormal heart rhythms.
• Kidney disease. Some studies found benefits in dogs, such as less protein in the urine. The evidence in cats is thinner.

Who should talk to the vet first

Everyone, really. Tufts says to always check with your veterinarian before starting omega-3s, because:

• the dose differs by condition;
• many pet foods already contain omega-3s, so your vet can work out whether to add more;
• omega-3s may not suit pets with gastrointestinal or bleeding disorders;
• it's not a cure-all. Pets with heart, kidney or joint disease need a diagnosis and usually medication.

How to choose a product

Pick a fish oil made for pets that states its EPA and DHA amounts, so your vet can calculate a dose. Liquids are easy to adjust for different sizes and mix into food. Stick to the dose your vet gives you rather than the bottle's general guide.

If joint stiffness is the reason you're looking, fish oil often goes alongside a joint chew. See how the options compare in Best Dog Health Supplements and our joint supplement evidence check.

Source: Tufts University Cummings School of Veterinary Medicine, Petfoodology, "Should I give fish oil to my pet?"