Deworming side effects: what is normal and when to call the vet

Introduction

Most pets tolerate worming well. Mild tummy upset can happen, especially the first time or if given on an empty stomach. Below is a simple guide to what is normal and when to seek help. This post was prepared with input from our lead vet and founder, Dr. Feargus McConnell, BVSc.

Common, mild effects (usually settle within 24–48 hours)

• Soft stools or a single vomit

• Brief drooling in cats from taste

• Reduced appetite for a meal or two

• Tiredness the day of dosing

Simple care at home

• Offer small meals and fresh water.

• Do not re-dose unless your vet advises.

• Keep dosing on schedule next month.

• If you gave a tablet on an empty stomach and your label allows, try with food next time.

When to call your vet

• Repeated vomiting or diarrhoea, blood in stool, or your pet seems very flat

• Swelling of the face, hives, collapse, or trouble breathing

• Your pet is very young, very small, elderly, pregnant, breeding, or has known health issues

• You think the wrong product or weight band was used

Prevent problems next time

• Weigh your pet and choose the correct weight band.

• Follow minimum age rules on the pack.

• Avoid stacking multiple medicines on the same day unless your vet says it is safe.

• For spot-ons, keep the coat dry for the label period after application.

• Keep products out of reach so pets do not chew extra doses.

Products we trust

• Dogs: Simparica Trio Chewable Tablet for Dogs — monthly chew with heartworm prevention and common intestinal worms, plus fleas and ticks when used as directed.

• Cats: Revolution Plus Spot-On for Cats — monthly spot-on that covers roundworm and hookworm in cats, with fleas, ticks and mites when used as directed.

• Cats: Revolution Topical Solution for Cats — monthly spot-on with heartworm prevention, fleas and mites.

FAQ

My pet vomited once after worming. Is that normal?
A single vomit can happen. Offer a small meal later and monitor. Call your vet if vomiting repeats.

I used a spot-on and my cat is drooling. What now?
Some cats drool if they lick the application site. Keep the site hard to reach and apply to clean, dry skin next time. Call your vet if drooling persists.

Can I give worming with food?
If your label allows, yes. Many pets handle doses better with food.

Still worried about a reaction or unsure what to do next?
Tell us your pet’s age, weight, and what you gave and we will help with next steps — contact us.

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