Krill oil in animals versus fish oil
Krill oil in dogs and cats compared with fish oil: efficacy, evidence, safety and interactions based on animal studies.
Short & honest
Krill oil provides EPA and DHA in a potentially more absorbable form than fish oil, but evidence that this confers a clinically relevant benefit in dogs and cats is currently lacking. Evidence grade C (weak).
Safety assessment: Safe when used correctly
Veterinary review not yet completed
This page is awaiting review by a registered veterinary surgeon. Until then, treat the text as education based on the sources listed — not as a verified veterinary judgement.
What is krill oil?
Krill oil is extracted from Antarctic krill (Euphausia superba), small crustacean-like animals. Like fish oil, it contains the omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), but in a different molecular structure: phospholipids instead of the triglycerides found in standard fish oil. In addition, krill oil contains astaxanthin, a red-coloured antioxidant.
Claim versus evidence
Better absorption than fish oil?
The phospholipid-bound omega-3s would be absorbed more efficiently by the body than triglyceride-bound omega-3s. An RCT in Alaskan Huskies (n=20) indeed showed that feed supplemented with krill meal increased the omega-3 index significantly more strongly than fish oil (from 3.9% to 6.3% versus from 3.9% to 4.7%), with EPA levels also being higher in the krill group [1]. This is an interesting biochemical signal, but it concerns sled dogs, a small sample, and krill meal is not the same product as a krill oil supplement.
Clinical benefit in dogs?
For omega-3 supplementation in general in dogs, there is sound evidence for reduction of inflammation and relief of joint pain [2]. However, the additional clinical benefit of krill oil over fish oil has not been demonstrated in any study in dogs. Better absorption does not automatically lead to better clinical results at therapeutic dosing.
Krill oil in cats
A randomised pilot study in cats with chronic gingivostomatitis (n=16, 28 days) showed that omega-3-rich lickable treats based on krill oil were well tolerated, but did not provide a statistically significant clinical improvement compared to control [3]. The study was too small and too short to draw definitive conclusions.
Astaxanthin
Krill oil contains astaxanthin, a powerful antioxidant. The clinical relevance of this for dogs and cats has not been substantiated in trials and remains theoretical for now.
Krill oil versus fish oil: practical comparison
| Property | Krill oil | Fish oil |
|---|---|---|
| Omega-3 form | Phospholipids | Triglycerides |
| EPA+DHA per gram | Lower | Higher |
| Antioxidant | Astaxanthin present | Not present |
| Cost per mg omega-3 | Higher | Lower |
| Evidence of clinical benefit dog/cat | Limited (C) | Moderate for inflammation/pain (B) |
Because krill oil is less concentrated in EPA and DHA per gram, larger volumes are needed for a therapeutic dose — which makes it more expensive per milligram of active substance.
Safety
Krill oil is generally well tolerated in dogs and cats. Krill is a crustacean; caution is advised in animals with a known crustacean sensitivity, although allergic reactions are rarely described. Omega-3s can prolong bleeding time and delay wound healing at high dosages. Consultation with a veterinary surgeon is indicated if there is doubt about the dose, especially when used concurrently with other medicines.
Conclusion
Krill oil is a safe supplement that provides biologically active omega-3s to dogs and cats, possibly in a better absorbable form. However, evidence that this also leads to better clinical outcomes than standard fish oil in companion animals is lacking. For anyone considering omega-3 supplementation for a specific condition, consultation with the veterinary surgeon is the appropriate first step.
Why this verdict?
The evidence grade is C (weak). There is one small RCT in sled dogs demonstrating better omega-3 uptake compared with fish oil, and one small pilot study in cats that showed no statistically significant clinical improvement. Both studies had small sample sizes, and direct comparative trials for clinical endpoints in companion animals are lacking.
Interactions with medication
- Anticoagulants (warfarin, heparin): omega-3s may enhance the blood-thinning effect — avoid combination or use only under veterinary supervision
- NSAIDs (e.g. meloxicam, carprofen): possible additive effect on bleeding time at high omega-3 doses
Legal status (Netherlands)
In the Netherlands, krill oil is available as a dietary supplement and animal feed ingredient. No registration as a veterinary medicinal product is required for supplementary use.
Sources
- [1] Higher omega-3 index after dietary inclusion of omega-3 phospholipids versus omega-3 triglycerides in Alaskan Huskies. Veterinary World, 2020. RCT doi:10.14202/vetworld.2020.1167-1173
- [2] The Effects of Omega-3 Supplementation on the Omega-3 Index and Quality of Life and Pain Scores in Dogs. Animals (Basel) — MDPI, 2024. Narrative review doi:10.3390/ani14213108
- [3] Efficacy and safety of omega-3-enriched lickable treats as adjunctive therapy for feline chronic gingivostomatitis: A randomized controlled trial. Veterinary World, 2025. RCT doi:10.14202/vetworld.2025.2344-2356
Questions about this substance for your animal?
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