Why a 4 kg dog's size changes everything
Your tiny dog's body weight makes even a corner of a bait block potentially lethal—toxic doses are calculated by milligrams per kilogram. What might cause mild illness in a 20 kg dog could be fatal for yours. The breakfast timing matters; if the dog ate recently, stomach contents may slow poison absorption slightly, buying you minutes to act.
Don't focus on the 'corner' estimation—chewing releases concentrated active ingredients from the bait matrix. Your dog likely ingested more toxin than the physical size suggests. Small breeds also metabolize poisons faster, sometimes accelerating symptom onset. Immediate vet contact is non-negotiable here.
The deceptive calm before bleeding begins
If this was an anticoagulant rodenticide (common in blocks), your dog will seem perfectly normal for 36-72 hours. The poison silently prevents blood clotting by interrupting vitamin K cycles—no vomiting, no diarrhea. By day 3 when weakness or pale gums appear, internal bleeding may already threaten organs.
Treatment must begin before symptoms. Vets often administer subcutaneous vitamin K1 to small dogs rather than oral doses to ensure absorption. Your dog will need strict activity restriction—no running or jumping—to prevent spontaneous bleeding during the 30-day treatment period.
When the block contains faster-acting poisons
Some rodenticides cause acute symptoms within hours rather than days. Zinc phosphide blocks release toxic gas when chewed, potentially causing your 4 kg dog to collapse with breathing difficulties before you finish reading this. Others like bromethalin attack the nervous system—watch for sudden clumsiness or exaggerated reflexes.
Small dogs show neurological signs sooner than larger ones. If the bait contained these faster poisons, every minute counts. Call your vet en route to the clinic; they may prepare lipid emulsion therapy or anticonvulsants. Bring the chewed block's remains in a sealed bag—some toxins require specific tests for detection.
Why you can't rely on internet dosage charts
Online rodenticide toxicity tables often provide misleading generalizations—formulations vary by brand and country. A 'corner' could mean 0.5 grams or 3 grams depending on block size. Your dog's individual health, age, and even diet (fat content affects some poison absorption) alter the risk calculation.
Veterinary toxicologists use complex formulas accounting for the poison's bioavailability and the dog's metabolic rate. Don't waste time searching for thresholds—small animal ERs stock antidotes for all common rodenticide types. If the bait's brand is unknown, assume the worst-case scenario and get moving.
The step-by-step response, from the first minute to the vet visit, is in our Rat Poison (Rodenticide) Poisoning emergency guide.