Fish Oil for Cats: Benefits, Dosage, Safety and How to Choose One

25 September 2026

Educational only; not a substitute for veterinary advice. If your cat has a medical condition or takes medication, speak to your vet before starting any supplement.

Fish oil is one of the most commonly used supplements for cats, and one of the most commonly misunderstood. The label says "omega 3", but what matters is how much EPA and DHA your cat actually gets, how fresh the oil is, and whether it is protected by enough vitamin E.

This guide covers each of those points, with doses by body weight.

At a glance

• Cats need EPA and DHA directly. Their bodies make almost none from plant oils such as flaxseed.
• A commonly cited supplemental range is 30–50 mg of combined EPA + DHA per kg of body weight per day.
• No safe upper limit has been published for cats, so more is not better.
• Choose a fish oil that lists EPA + DHA in mg, contains vitamin E, and can show an oxidation (TOTOX) result.

What is fish oil for cats?

Fish oil is the fat pressed and refined from oily fish. It is valued for two long-chain omega-3 fatty acids: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). DHA is a structural fat in the brain and retina. EPA is involved in the body's signalling around normal inflammatory responses.

"Omega 3 for cats", "fish oil for cats" and "salmon oil for cats" all describe the same category. What separates products is the fish species, the EPA + DHA concentration, and the quality control behind the bottle.

Why cats can't rely on plant omega-3s

Dogs and people can convert small amounts of plant omega-3 (ALA, found in flaxseed and chia) into EPA. Cats essentially can't: their activity of the delta-6 desaturase enzyme is so low that conversion is "virtually zero" (see Today's Veterinary Practice).

For a cat, the omega-3s that count come ready-made from marine sources. Most dry foods contain modest amounts, which is why many owners add a marine oil.

Benefits of fish oil for cats

The EPA and DHA in fish oil are used by veterinarians and pet owners to support:

• Skin and coat. The most commonly reported change is a softer, glossier coat and less dry, flaky skin, usually after 3–4 weeks of consistent use.
• Joint comfort and mobility. EPA supports the body's normal inflammatory balance, which matters for older, less active cats.
• Brain and eye health. DHA is a building block of brain and retinal tissue throughout life.
• Healthy ageing. Fish oil is often part of a broader routine for senior cats, alongside nutrients such as CoQ10, taurine and L-carnitine.

Fish oil is a nutritional supplement, not a medicine. If your cat has a diagnosed condition, your vet may recommend a specific therapeutic dose and monitoring.

How much fish oil should a cat have?

Dose by EPA + DHA, not by "fish oil" or "total omega-3". A 1,000 mg fish oil capsule typically holds only around 300 mg of EPA + DHA. The rest is other fats.

A commonly cited range for supplementing cats is 30–50 mg of combined EPA + DHA per kg of body weight per day (Today's Veterinary Practice).

Three practical rules:

1. Check your cat's food first. Some diets, especially those formulated for skin or joints, already contain meaningful EPA + DHA. Adding more can push intake higher than intended.
2. Start low. Introduce the oil gradually over the first week to avoid a loose stool.
3. More is not better. No safe upper limit has been published for cats (Today's Veterinary Practice), so stay within the range above unless your vet advises otherwise.

With Pawever Omega Oil, a cat's serving is 1 pump daily, providing a minimum of 460 mg EPA+DHA per 2.5 mL pump.

Is fish oil safe for cats? Side effects to know

At sensible doses fish oil is well tolerated by most cats. Reported side effects include (Today's Veterinary Practice):

• vomiting or loose stools, usually from starting too fast
• fishy breath
• reduced platelet function and slower wound healing at high intakes
• interactions with medicines that affect clotting, such as aspirin

Tell your vet your cat takes fish oil before any surgery, and check with them first if your cat has a bleeding disorder or gut condition, or is on medication.

Why vitamin E matters in fish oil for cats

Omega-3 fats oxidise easily. When a cat takes in a lot of unsaturated fat without enough vitamin E to protect it, the result can be steatitis ("yellow fat disease"), a painful inflammation of body fat. It is historically linked to fish-heavy, vitamin E-poor diets.

The risk is low with a well-formulated supplement. The practical rule is simple: only use a fish oil for cats that contains added vitamin E (often listed as "mixed tocopherols"). We cover this in more depth in salmon oil vs small-fish oil.

Salmon oil vs anchovy oil for cats

Salmon oil is the most popular choice in the UK and US, and it works. The trade-offs are:

Whatever the fish, what matters most is what the label and test results say: EPA + DHA in mg, added vitamin E, and oxidation results.

How to choose the best fish oil for your cat

Use this five-point checklist:

1. EPA + DHA listed in mg per serving. "1,000 mg fish oil" tells you almost nothing.
2. Vitamin E included. Look for mixed tocopherols on the ingredient list.
3. Oxidation tested. Ask for the TOTOX value. The industry benchmark (GOED) is a TOTOX below 26 (PMC review); lower means fresher.
4. Contaminant tested. Heavy metals and other contaminants should be tested by an independent lab.
5. Easy to dose. Most cats won't take a capsule. A liquid you can measure onto food is far easier to give every day.

How Pawever Omega Oil measures up

Pawever Omega Oil is made from wild-caught anchovy oil, protected with mixed tocopherols (vitamin E) and astaxanthin. One pump daily for your cat will provide a minimum of 460 mg EPA+DHA.

Certificate of analysis is available for our Omega Oil on request, with our latest showing TOTOX of 3.77 (well inside the GOED limit of 26) and a clean contaminant panel.

Our Omega Oil comes in a pump bottle, so every serving is measured and goes straight onto food, with no pilling. It pairs with Pawever Plus for Cats, our daily joint and healthy-ageing capsule, which no longer contains fish oil so the two can be used together. New to it? Read the Omega Oil introduction.

Shop Pawever Omega Oil → 60-day money-back guarantee.

FAQ

Can I give my cat human fish oil? It is possible, but not ideal. Human capsules are hard to give to a cat, may contain flavourings or added ingredients, and the dose is not scaled to a 4 kg animal. Some also lack enough vitamin E.

How long does fish oil take to work in cats? Omega-3s build up in the body over weeks. Owners typically notice coat changes after 3–4 weeks; mobility-related changes, if any, usually take 4–8 weeks of consistent use.

Is salmon oil or fish oil better for cats? Neither label is automatically better. Compare EPA + DHA per serving, vitamin E content and oxidation results. Small fish such as anchovies tend to accumulate fewer contaminants than salmon.

Can fish oil upset my cat's stomach? It can if you start at the full dose. Introduce it gradually over a week, and stop and speak to your vet if vomiting or diarrhoea continues.

Can I give fish oil with my cat's other supplements? Usually yes, but add up the EPA + DHA from all sources, including the food. If your cat takes medication, check with your vet.

Do dogs need a different dose? Yes. Dogs are dosed differently. See our fish oil for dogs dosage chart.

Sources

• Role of dietary fatty acids in dogs and cats — Today's Veterinary Practice
• Fish oil supplements, oxidative status, and compliance behaviour — PMC
• Lenox CE, Bauer JE. Potential adverse effects of omega-3 fatty acids in dogs and cats. J Vet Intern Med 2013 (summary, dvm360)

This product is not intended to diagnose, treat, cure, or prevent any disease.