My cat stole a bite of my dinner that had herring in a creamy dill sauce — should I be worried?

You should be mildly concerned, but it's not an emergency. Plain, cooked herring itself is safe for cats, but the creamy dill sauce is the problem — it likely contains ingredients like butter, cream, salt, and seasonings that can upset a cat's stomach. Watch your cat closely for signs of gastrointestinal distress, such as vomiting, diarrhea, or loss of appetite, over the next 24 hours. Pickled or heavily salted herring is unsafe, but a small amount of sauce-coated fish from one bite may just cause a mild tummy ache. Offer plenty of water and call your vet if any worrying symptoms appear.