Suspect poisoning? US: ASPCA Poison Control (888) 426-4435 · UK: 01202 509 000 · Severe symptoms → nearest emergency vet now.

My cat had a small piece of plain cooked herring last night and has soft stool today. Is it related?

Cats · Food safety

Last reviewed: 2026-09-05 · Reference ranges: ASPCA, Pet Poison Helpline & Merck Veterinary Manual

Short answer

It's very likely the herring caused the soft stool, but it's not a poisoning emergency. A new protein can upset a cat's stomach, even if the fish itself is safe. The stool should firm up within a day or two as the fish passes through. Offer plenty of fresh water and skip any extra treats. If the diarrhea continues for more than 48 hours or your cat acts lethargic, call your own vet.

Herring — Food safety facts

Safe to share · Cats · full breakdown on the linked food page

Cooked plain herring is fine. Pickled or salted herring is not.

Dogs and cats carry the same rating (Safe to share), so the notes below hold for either pet.

Herring is not toxic to cats. The real limit is calories, fat and salt, so treat it as a small extra alongside the normal ration rather than a meal in itself.

There is no poisoning risk here, and the usual problem is simply eating too much at once: a heavy fat or salt load can bring on loose stools or a single vomit. Offer water, keep an eye on the pet for 24 hours, and do not induce vomiting.

Why these cautions matter

A heavy salt load drives up thirst and urination, and in the worst cases leads to sodium ion poisoning, which is a genuine emergency.

Herring can stay on the rotation, but only as an extra mouthful: keep the rest of the day's food unchanged and watch the litter box and how quickly they finish the next meal.

The full verdict, portion guidance and serving notes are collected on the Herring food facts page.

Open the full food page: Herring food facts →