Is Fish Oil Good for Cats?

The Short Answer

Yes, absolutely. Fish oil is one of the few supplements that almost every veterinarian agrees on. It is a powerhouse for reducing inflammation, improving coat quality, and supporting older cats with arthritis or kidney disease.

But there is a catch: Quality is everything.

Giving your cat cheap, oxidized (rancid) fish oil is worse than giving them nothing at all. Rancid oil increases inflammation and introduces free radicals into their body. You need a product that is third-party tested for purity and freshness.

Why This Matters

Cats are obligate carnivores, meaning they need nutrients from animal sources. They are terrible at converting plant-based Omega-3s (like flaxseed oil) into the active forms they need (EPA and DHA). Fish oil gives them these nutrients directly.

Inflammation is the enemy.

Chronic inflammation drives many common feline issues—itchy skin, stiff joints, and kidney failure. The EPA and DHA in fish oil act as a "fire extinguisher" for this inflammation.

Your cat's food probably isn't enough.

Even "Omega-rich" kibble often falls short. The high heat used to process dry food destroys fragile fatty acids. By the time the bag sits in a warehouse for months, the "Omega-3s" on the label may be biologically useless. Is Kibble Bad For Cats

What's Actually In Fish Oil

Not all "marine oils" are the same. Here is what you are actually feeding your cat:

• EPA (Eicosapentaenoic Acid) — The anti-inflammatory heavy lifter. This is what helps with skin allergies and arthritis.
• DHA (Docosahexaenoic Acid) — Critical for brain and eye health. Essential for kittens and senior cats with cognitive decline.
• Vitamin E — Crucial addition. Processing fish oil removes natural Vitamin E. Good brands add it back in because metabolizing fish oil uses up your cat's Vitamin E stores. Do Cats Need Supplements

What to Look For

Green Flags:

• Small Fish Source — Sardines, anchovies, and mackerel live shorter lives, meaning they accumulate fewer heavy metals (mercury) than salmon or tuna.
• Dark Glass or Opaque Plastic — Light destroys fish oil. If you can see the oil through the bottle, put it back.
• IFOS Certification — The "International Fish Oil Standards" 5-star rating is the gold standard for purity and potency.
• Pump or Airless Dispenser — Oxygen causes rancidity. Pumps keep air out better than screw-top caps.

Red Flags:

• "Cod Liver Oil" — DANGER. Liver oils are high in Vitamin A. Cats are sensitive to Vitamin A toxicity, which can cause permanent bone deformities. Stick to "fish body oil."
• "Fish Oil" (Generic) — If the label doesn't say what fish it is, it's likely a bottom-of-the-barrel blend.
• Clear Bottles — A guarantee that the oil has been damaged by UV light before you even bought it.
• Citrus Flavoring — Often used to mask the smell of rancid oil. Cats generally hate citrus anyway.

The Smell Test

Before you feed it, smell it.

• Good Fish Oil: Smells faintly of fresh ocean or raw fish. It should be mild.
• Bad Fish Oil: Smells sour, sharp, or like rotting fruit. If it makes you gag, it will make your cat sick. Throw it away.

The Best Options

Focus on small cold-water fish oils packaged to prevent oxidation.

The Bottom Line

1. Start small. Introduce fish oil slowly to avoid diarrhea. Aim for 30-50mg of combined EPA/DHA per kg of body weight daily.

2. Buy small bottles. Fish oil starts oxidizing the moment you open it. Buy a size you can finish in 30-60 days.

3. Keep it cold. Always store liquid fish oil in the refrigerator.

4. Watch for recalls. In 2023, a major recall (Stratford Care USA) highlighted the dangers of Vitamin A toxicity in poorly formulated supplements. Stick to reputable brands.

FAQ

Can I give my cat human fish oil?

Depends. If it's a high-quality liquid or capsule without added flavorings (like lemon or rosemary) or sweeteners (xylitol is toxic to dogs, though less so to cats, it's best to avoid), it's physically safe. However, dosing is tricky. Human capsules are often 1000mg—way too much for a cat. You'd need to puncture it and use a fraction of the oil.

Does fish oil cause bleeding?

Rarely. At extremely high doses, fish oil can thin the blood. If your cat is on blood thinners or about to have surgery, stop fish oil 2 weeks prior.

What about Krill Oil?

It's great but expensive. Krill oil contains astaxanthin (a powerful antioxidant) and is often more "bioavailable" than fish oil. It's a fantastic option if you can afford it, but high-quality sardine/anchovy oil is 90% as good for 50% of the price.

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