Krill Oil

Krill oil is extracted from Antarctic krill, Euphausia superba, a small shrimp-like crustacean that exists in enormous biomass in the Southern Ocean. Like fish oil it supplies the long-chain omega-3 fatty acids EPA and DHA. What differs is the packaging, and whether that difference justifies the price is the question this entry exists to answer.

What Makes It Different

• Phospholipid form. In fish oil, EPA and DHA are bound as triglycerides. In krill oil a large proportion is bound to phospholipids, the same class of molecule that makes up cell membranes. Phospholipid-bound fatty acids are water-dispersible, which improves how they are handled in the gut.

• Astaxanthin. The red carotenoid that gives krill oil its colour. It is a potent antioxidant and it also acts as a natural preservative within the oil, slowing the oxidation that plagues marine oils.

• Choline. The phospholipids are largely phosphatidylcholine, so krill oil supplies choline as well.

The Honest Comparison With Fish Oil

Here is the trade-off stated plainly, because most marketing gives you one half of it.

In krill oil's favour: the phospholipid form appears to be absorbed at least as well and possibly better per milligram of EPA and DHA than triglyceride fish oil, so you may need somewhat less. The astaxanthin is a genuine addition and helps with stability. Krill oil is generally less prone to the fishy aftertaste and burping that owners complain about with fish oil.

Against it: krill oil is much lower in total EPA and DHA per gram than a concentrated fish oil — typically a fraction of what a good fish oil delivers. Combined with a substantially higher price per bottle, the cost per milligram of omega-3 is several times that of fish oil, and any absorption advantage does not close that gap. For a large dog needing a meaningful omega-3 intake, krill oil often becomes impractical on cost alone.

And critically: the evidence base is for omega-3, not for krill specifically. The canine research showing benefit — including a 2022 systematic review and meta-analysis of supplements for canine and feline osteoarthritis, which found clear analgesic efficacy for omega-3-enriched diets and omega-3 supplements, and to a lesser degree for cannabidiol — was built largely on fish oil and omega-3-enriched diets. Nobody has demonstrated that krill oil outperforms fish oil clinically in dogs. If your goal is to deliver EPA and DHA to a dog with stiff joints, fish oil is the evidence-backed and cheaper route. Krill oil is a reasonable choice for a small animal, a fussy one, or where the astaxanthin and better palatability matter to you.

What the Canine Krill Research Actually Shows

There is one canine study most krill pages lean on, and it is worth knowing what it did and did not test. In a 2020 study in Veterinary World, Burri and colleagues fed 20 healthy Alaskan Huskies the same kibble plus 1.7 grams of EPA and DHA a day for six weeks. Ten dogs got it from krill meal and ten from fish oil.

The omega-3 index — the share of EPA and DHA in red blood cell membranes — rose from 3.9 to 6.3 percent in the krill group, against 3.9 to 4.7 percent on fish oil.

• What it supports: at the same EPA and DHA intake, the phospholipid form got more omega-3 into the dogs’ cells. That matches the absorption point above.

• What it does not show: any difference in joints, skin or health. It measured a blood marker, in young healthy working dogs, over six weeks, with ten dogs per group.

• One more detail: it used krill meal, not krill oil, and matched the two groups on EPA and DHA. That is exactly how you should compare products too — by milligrams of EPA plus DHA, not by capsule count.

How Much to Give

Dose by combined EPA plus DHA, never by oil volume. This is the mistake that makes most omega-3 supplementation useless — two products at the same teaspoon dose can differ fivefold in what they actually deliver. Read the panel for the EPA and DHA figures and add them.

Body weight · General wellness, EPA+DHA · Joint support, EPA+DHA

• 10 lbs — 100 to 150 mg — 200 to 450 mg

• 25 lbs — 250 to 350 mg — 550 to 1,100 mg

• 50 lbs — 450 to 700 mg — 1,100 to 2,250 mg

• 75 lbs — 700 to 1,000 mg — 1,700 to 3,400 mg

• 100 lbs — 900 to 1,400 mg — 2,250 to 4,500 mg

• Cat, 10 lbs — 100 to 200 mg — Vet-directed

The wellness column is roughly 20 to 30 mg per kilogram of body weight; the joint column is the higher therapeutic range of about 50 to 100 mg per kilogram used in the osteoarthritis literature. Look at the joint column for a 75 lb dog and then look at the EPA and DHA content of a krill oil capsule, and the cost problem becomes concrete very quickly.

How to Give It

With food, and with fat in the meal. Split larger amounts across two meals to reduce loose stool. Build up over one to two weeks rather than starting at the full amount. Judge joint effects over eight to twelve weeks — omega-3 needs to incorporate into cell membranes before it changes anything, and this is not a supplement that shows you results in a week.

Store it in the fridge once opened and keep it away from light and heat.

Dogs, Cats and Horses

Cats take it well and often prefer it to fish oil. Small amounts, and note the shellfish consideration below.

Horses are given omega-3 for inflammatory airway disease, skin conditions and joint support, but krill oil is not the practical vehicle — the volumes a 500 kg animal requires make it prohibitively expensive. Marine algae oil or flaxseed are the realistic equine options, with the caveat that flax supplies ALA which horses convert to EPA and DHA only inefficiently. Our equine research covers what we have studied in horses.

Beyond Joints: Skin, Kidneys and Heart

Krill oil’s value is its EPA and DHA, so the uses are the same as for any omega-3 source. VCA Animal Hospitals’ omega-3 fish oil guide lists skin allergies and dermatitis, arthritis, kidney disease, heart disease and inflammatory bowel disease among the conditions vets use omega-3 for. That evidence was built mostly on fish oil, and krill oil delivers the same fatty acids.

• Skin and coat is the most common reason owners reach for it, and the place where lower wellness amounts are usually used. Judge it over two to three months, since new coat has to grow in.

• Kidney and heart disease are veterinary conditions. Omega-3 may be part of the plan, but the amount and the product should come from your vet, who can account for the diet and any drugs.

• Don’t double up by accident. Many prescription and senior diets are already omega-3 enriched. Count what the food supplies before adding more.

What to Look For When Buying

• EPA and DHA in milligrams per capsule or millilitre, stated separately. If a label only gives total krill oil, you cannot dose it.

• Astaxanthin content stated, and a deep red colour.

• Freshness indicators. Oxidised marine oil is not merely less effective — it is pro-oxidant, meaning a rancid product does the opposite of what you bought it for. Check dates, prefer nitrogen-flushed or sealed capsules, and smell it. Sharp, paint-like or strongly rancid means bin it.

• MSC certification. Antarctic krill sits at the base of the Southern Ocean food web and is the primary food source for whales, seals, penguins and seabirds. Whether the fishery is sustainably managed is a real question, not a marketing flourish, and Marine Stewardship Council certification is the available signal.

• Third-party purity testing for heavy metals — krill are short-lived and low in the food chain, so accumulation is less of a concern than with large fish, but verification still matters. Our own certificates of analysis exist on the same principle, explained in our COA entry.

Side Effects and Cautions

• Shellfish. Krill are crustaceans. Avoid krill oil in any animal with a known shellfish or crustacean sensitivity, and consider fish oil or algae oil instead.

• Bleeding risk. Omega-3 fatty acids inhibit platelet aggregation. Stop before surgery or dental work, and use caution alongside NSAIDs, aspirin or anticoagulants, or in animals with a bleeding disorder.

• Vitamin E requirement rises. Polyunsaturated fats are exactly what vitamin E protects from oxidation, so a generous omega-3 regimen increases the need for it. Our vitamin E entry covers this, including feline steatitis, the condition that results from getting the ratio badly wrong.

• Loose stool and digestive upset, usually from starting too high.

• Calories. Oil is fat, and therapeutic omega-3 amounts for a large dog add up. Adjust the ration.

• Pancreatitis history — added fat is a consideration. Ask your vet.

• Rancidity, covered above, which is the most common way owners waste money here.

Drug Interactions, Missed Doses and Warning Signs

Because krill oil delivers the same EPA and DHA as fish oil, the omega-3 guidance applies. VCA’s fish oil monograph flags interactions with anticoagulants such as warfarin, NSAIDs and the chemotherapy drug doxorubicin. It also advises caution in diabetic animals, those with diarrhoea, and pregnant or nursing animals.

• Stop and call your vet for signs of an allergic reaction — facial swelling, rash, irregular breathing. Call too for abnormal bruising or bleeding (VCA notes this especially in cats), vomiting with belly pain that could mean pancreatitis, or loss of appetite.

• Milder effects include fishy breath, an oily coat and mild stomach upset. These usually settle with a lower amount given with food.

• Missed a dose? Give it when you remember, unless the next one is nearly due. Then skip it. Never double up.

When to Talk to Your Veterinarian

Before any surgical or dental procedure, and before combining omega-3 with NSAIDs or anticoagulants. Before starting it in an animal with a history of pancreatitis or on a fat-restricted diet. And if you are supplementing for joints, get the diagnosis first — omega-3 supports a pain management plan rather than replacing one, and a dog whose mobility is deteriorating needs an examination. Our page on joint and mobility covers what our own research found.

How It Fits With Hemp

This is one of the better-supported combinations we can point to, and the reason is in the systematic review mentioned above: the same 2022 analysis of canine and feline osteoarthritis supplements found clear analgesic efficacy for omega-3 supplements and, to a lesser degree, for cannabidiol — while concluding that glucosamine and chondroitin should no longer be recommended for this purpose. Those are the review's findings rather than our claims, and we present them as such. But it does mean an owner running omega-3 alongside hemp for an older stiff dog is using the two ingredients that came out of that appraisal best.

Practically, they go together neatly: both are oils, both need dietary fat to absorb, and both can go on the same meal. One shared caution — both affect platelet function, so disclose both before surgery. Our serving guide has hemp amounts by weight, and the clinical trials page covers our own studies.

Frequently Asked Questions

Is krill oil better than fish oil for dogs? Better absorbed per milligram, and it includes astaxanthin. But it contains far less EPA and DHA per gram and costs several times more per milligram of omega-3, and no canine study shows it outperforms fish oil clinically.

How much krill oil should I give my dog? Dose by combined EPA plus DHA, not by volume. Roughly 20 to 30 mg per kilogram daily for wellness, and 50 to 100 mg per kilogram for joint support. Read the panel and add the two figures.

How long does krill oil take to work? Eight to twelve weeks for joint effects. Omega-3 has to incorporate into cell membranes first, so this is not a fast-acting supplement.

Can dogs with shellfish allergies have krill oil? No. Krill are crustaceans. Use fish oil or marine algae oil instead.

Do I need to stop krill oil before surgery? Yes. Omega-3 inhibits platelet aggregation, so tell your vet and follow their timing, typically stopping one to two weeks beforehand.

How can I tell if my krill oil has gone off? Smell it. Sharp, paint-like or strongly rancid means discard it. Oxidised marine oil is pro-oxidant, so a rancid product is worse than none at all.

For the canine joint evidence, see the 2022 systematic review and meta-analysis on nutraceuticals and diets for canine and feline osteoarthritis. On the fishery itself, the Marine Stewardship Council publishes its assessment of the Antarctic krill fishery.

Can I give my dog human krill oil?

Often yes, provided the only ingredient is krill oil and you dose by the EPA plus DHA figure on the panel rather than by capsule. Avoid flavoured chews or gummies unless you have checked for xylitol, and check capsule size — a large capsule can be hard for a small dog or cat.

Can I give krill oil with other joint supplements?

Yes. It sits comfortably with glucosamine, boswellia and hemp. Just don’t stack it on fish oil or green-lipped mussel without adding up the total omega-3. Tell your vet if your dog is on an NSAID.

Is krill oil safe for cats?

Generally yes, in small amounts, and many cats accept it more readily than fish oil. Skip it for any cat with a shellfish sensitivity, and watch for unusual bruising or bleeding, which VCA flags especially in cats on omega-3.