Salmon Oil vs Krill Oil for Cats

At the clinic front desk, the omega-3 question usually came from someone holding a bottle of their own supplement. They’d bought krill oil for themselves, a friend had said it was “better than fish oil,” and they wanted to know whether a few drops would help their cat’s dull coat. The honest answer was more boring than the question. Salmon oil wins for most cats because you can find one made for them, with a pump and a label that tells you what’s inside. Krill oil has a clever delivery story, but the best data is in dogs and the cat-labeled products are hard to find.

You’ll notice there’s no krill card. When I searched Amazon for krill oil made for cats, the results were human softgels and unrelated cat chews. I’m not going to point you at a human supplement and guess a feline dose, so krill gets covered in the text only.

	Salmon oil	Krill oil
Where it comes from	Oil pressed from salmon (often blended with other fish oils)	Oil from krill, a small crustacean
How the omega-3 is carried	Mostly bound to triglycerides	Largely bound to phospholipids
Best evidence	Fish oil as a category has the most pet research	One small dog study, run by a krill company
Cat-labeled products on Amazon	Several, including pump bottles	None that I could find
Main catch	Dose depends on EPA and DHA, which labels don’t always state	Shellfish source, and no established cat dose
Best fit	Most cats whose owners want a marine omega-3 for the coat	A cat whose vet specifically suggests it

The short version

• Cornell’s Feline Health Center says fatty acid supplements may help skin and coat but are not 100 percent effective, and that too much can cause harm.¹
• Vets count the dose in milligrams of EPA plus DHA, not in milliliters of oil, and published therapeutic data in cats is thin.²
• The one head-to-head I found put krill meal against fish oil in 20 sled-type dogs. Krill raised the omega-3 index more, and the authors worked for the krill company.³
• Start with a cat-labeled liquid such as Nordic Naturals Omega-3 Cat or a pump-style Zesty Paws salmon oil, and ask your vet for the dose.

What each one is

Both oils are marine sources of the same two long-chain omega-3 fats, EPA and DHA. Salmon oil is pressed from fish, and pet versions are often blends. The Zesty Paws bottle lists pollock oil and salmon oil plus mixed tocopherols as a preservative, so “salmon oil” on the front is a shorthand for a blend.⁴ Krill oil comes from a tiny crustacean, and its omega-3s sit mostly on phospholipids instead of triglycerides. That’s the whole pitch behind the “better than fish oil” claim you hear in the supplement aisle.

For an indoor cat, the question that matters isn’t which molecule is fancier. It’s whether the product is made for a cat, whether you can see what’s in a serving and whether the dose is something your vet has signed off on.

What the research covers (and what it doesn’t)

Here’s the part that surprised me when I went looking. The krill-versus-fish comparison that gets quoted most was done in dogs, not cats. Researchers split 20 Alaskan Huskies into two groups for six weeks, with each group getting 1.7 grams of EPA and DHA daily from either krill meal or fish oil. The krill group’s omega-3 index rose from 3.9 to 6.3 percent, while the fish oil group’s rose from 3.9 to 4.7 percent.³ It’s a real result. It’s also a small trial, it measured blood levels and not coat quality, and the authors were employed by the company that sells the krill ingredient.³

For cats, the picture is thinner for both oils. A 2020 review in Today’s Veterinary Practice, written by two board-certified veterinary nutritionists, says therapeutic omega-3 data in cats is scarce and gives its dose estimates as EPA plus DHA per kilogram of body weight, not as “a pump” of oil.² The same paper lists the possible downsides of too much: stomach upset, altered platelet function, weight gain and effects on the immune system.² Cornell’s skin page lands in a similar place. Fatty acids may help, they aren’t a guaranteed fix, and more is not better.¹

Reading the label

The review’s practical advice applies to any bottle you buy: the therapeutic dose is based on the milligrams of EPA and DHA, not the total oil.² That’s where cheap labels cause trouble. The Zesty Paws product page says the oil is rich in EPA and DHA but, on the text I could read, gave no amount per pump and no cat-specific dose.⁴ The numbers may be on the label image, so check the bottle itself, and if they aren’t there, ask the maker. A product that can’t tell you its EPA and DHA content can’t be dosed against a vet’s number.

Krill adds one more thing to check. Krill are crustaceans, so a cat with a history of food reactions is a question for your vet before the first drop, not after. And because I found no krill oil sold for cats, any krill product would be a human or dog supplement that someone has to convert, which is how overdoses happen.

Which one for an indoor cat

Indoor cats tend to be the ones with the quiet coat problems, such as dry flakes along the spine in winter when the heat is on. Before any oil, I’d look at the diet and the grooming routine. If you want to add something, a liquid you can measure beats a capsule you have to hide. That’s an argument for a cat-labeled bottle like Nordic Naturals Omega-3 Cat, or a pump bottle like Zesty Paws once your vet gives you a daily amount. Start with a small bottle. Fish oils go off, and a cat that smells rancid oil on its dinner will let you know. If you want a wider field, our best omega-3 supplements for cats roundup covers the other bottles.

How I compared them

I haven’t run these side by side with a cat, so I won’t claim I did. What I did instead was read Cornell’s skin disorder page, the Today’s Veterinary Practice dosing review and the krill-versus-fish dog trial, then read the maker’s listing for the salmon oil and searched Amazon for a cat-labeled krill oil. Krill earns a real point on the science. Phospholipid-bound omega-3 raised blood levels further in that trial, and if a cat-specific krill product with a published dose existed, I’d want to look at it again. Today the trade-off is a possible bioavailability edge against no cat product, no cat data and a shellfish source, and that doesn’t beat a labeled fish oil.

Common questions

Can I give my cat my own krill oil capsules? I wouldn’t. Human softgels are dosed for people, and the review stresses that cat doses are worked out by EPA and DHA per kilogram, so a guess is easy to get wrong.²

Is a dog-and-cat salmon oil fine for cats? Many are sold that way, including the Zesty Paws product, but the page I read gave no cat-specific dose, so your vet’s number is what you follow.⁴

How fast will the coat change? Cornell calls fatty acid supplements helpful for some cats but not reliably effective, so I’d treat any change as a bonus and not a promise.¹

When to talk to your vet

We’re not vets, and an omega-3 oil is not a treatment for a skin problem. If your cat has bald patches, scabs, constant scratching or sudden heavy shedding, see your vet before you buy anything, because those can come from allergies, parasites or other causes an oil won’t touch. Ask before starting any supplement if your cat takes medication, has a bleeding problem, has kidney disease or has ever reacted to seafood. Your vet can give you an EPA plus DHA dose in milligrams, which is the number you need to compare bottles.

The bottom line

• Choose salmon oil, such as Zesty Paws, if you want an easy pump-dispensed oil and you’re prepared to confirm the EPA and DHA amounts with the maker and your vet.
• Choose a cat-labeled fish oil, such as Nordic Naturals Omega-3 Cat, if you’d rather start with a product sold for cats in a small bottle.
• Choose krill oil only if your vet recommends a specific product and dose, since there’s no cat-labeled option I could verify.

For most cats, a labeled fish oil at a vet-approved dose is where I’d begin.

More coat and skin guides

• Best omega-3 supplements for cats
• Do omega-3 supplements help cats’ skin and coat?
• Are omega-3 supplements safe for cats?