General info on possible krill oil for dogs side effects.
You should keep in mind that when you start giving fatty acid supplements to your dog there may be side effects.
The worst case scenario is very rare but still might occur: it is pancreatic. Outside symptoms are vomiting and diarrhea, followed by a quick dehydration.
So if you notice any of those symptoms, please contact a veterinarian, describing dog’s preceding diet in detail. It’s very possible that the cause of this condition is different than the krill oil capsules you’ve given your dog. Most probably improper nutrition has led to that over time and you need to balance out the diet for your dog once and forever, so do that with a veterinarian.
You can avoid these side effects by shaping the dog’s diet better. If you start supplementing fatty acids, i.e. start giving your dog krill oil or fish oil, you might want to cut down on other high-fat foods. This way you will reduce calories by feeding your dog a lower calorie food.