207 mg/kg is the lethal line; a pellet is only 2% to 4% of that weight
Metaldehyde kills cats at an oral LD50 of 207 mg/kg. Garden pellets carry 2% to 4% active ingredient, commercial blends up to 7%, Chinese garden granules commonly 6%. A 4 kg cat reaches the LD50 at about 41 g of 2% pellets, 21 g of 4%, or 14 g of 6%.
The number that matters at midnight is smaller. The ASPCA Animal Poison Control Center treats 2 mg/kg in dogs as grounds for decontamination, which for that cat is 0.4 g of 2% bait — a pinch, six or eight pellets. A level teaspoon of 2% bait weighs about 5 g and holds 100 mg, so one teaspoon is 25 mg/kg: an eighth of the lethal dose.
What else is in the bag
Metaldehyde is the active ingredient in more than 80% of slug and snail baits sold worldwide. The bran or molasses base exists to attract molluscs, and it attracts cats for the same reason. Some US baits add carbaryl, a carbamate that layers a second toxicity on the tremors. Granules and gels keep releasing metaldehyde for up to 14 days in damp weather, so a bed treated two weeks ago is live after rain.
The first three hours, stage by stage
Signs start 20 minutes to 6 hours after eating; the fast end means an empty stomach and a large dose.
| Stage | Time | What you see | Why it matters |
|---|---|---|---|
| Silent | 0–30 minutes | Nothing, drooling, or one vomit | Only window for decontamination |
| Tremor | 30 minutes–3 hours | Fine tremors, ear twitching, wobbly walk, wide pupils, nystagmus | Sedation and cooling start |
| Hyperthermia | 1–4 hours | Above 41.1 °C (normal 38.1–39.2), panting, brick-red gums | 41.1 °C damages cells, 41.6 °C kills them |
| Seizure | 3–6 hours | Rigid limbs, head pulled back, unresponsive | Airway, cooling, anaesthesia |
| Crisis | 4–24 hours | Respiratory failure, bleeding from several sites | Most deaths happen here |
| Recovery | 24–72 hours | Tremors fade, appetite returns | Good prognosis after 24 hours |
The dose table to read before the vet asks
LD50 means half the animals at that dose die, so surviving it is not being safe.
| Cat weight | LD50 (207 mg/kg) | 2% pellets | 4% pellets | 6% granules |
|---|---|---|---|---|
| 3 kg | 621 mg | 31 g | 16 g | 10 g |
| 4 kg | 828 mg | 41 g | 21 g | 14 g |
| 5 kg | 1,035 mg | 52 g | 26 g | 17 g |
| 6 kg | 1,242 mg | 62 g | 31 g | 21 g |
The 2 mg/kg threshold sits far lower: 6 mg for a 3 kg cat, 12 mg for a 6 kg cat. You cannot weigh that at 23:00 — estimate what is missing, photograph the label, and let the vet divide.
Nine things not to do in the first 30 minutes
- Do not use hydrogen peroxide. A twitching cat aspirates it; see when vomiting must not be induced.
- Do not give milk, oil, butter or salt water; none binds metaldehyde.
- Do not wait for a tremor. The silent half hour is the treatable one.
- Do not scruff and pin a trembling cat; restraint raises body temperature.
- Do not plunge it into cold water; cool wet towels on paws and belly, with a fan.
- Do not use human diazepam or an antihistamine from the cupboard.
- Do not pour water into the mouth; aspiration pneumonia is the usual second injury.
- Do not sweep up with the cat loose: carrier first, gloves, lidded bin.
- Do not drive without phoning; ask about oxygen, IV fluids and a tremor drug.
Pyrethroid flea products and rat bait look the same. If exposure is unclear, read trembling and weakness before blaming the garden.
What the vet can and cannot do
There is no antidote; everything below buys time to metabolise it.
- Decontamination: emesis only if still asymptomatic and inside about 30 minutes; lavage under anaesthesia for a large dose; charcoal only with a protected airway.
- Tremor control: a benzodiazepine first, methocarbamol if tremors break through, anaesthesia when drugs fail. One published cat needed propofol, midazolam and dexmedetomidine, stayed under 28 hours and went home on day 8 with no residual signs.
- Cooling and fluids: active cooling above 41.1 °C, IV fluids, bicarbonate once blood gas confirms acidosis.
- Aftercare: coagulation and liver enzymes for 2 to 3 days, because liver failure can surface 48 to 72 hours after tremors stop.
Budget first: a night exam plus facility fee runs near 271 USD, 204 GBP or 236 CNY before treatment. Our guide to the emergency night visit lists the add-ons worth questioning.
Alternatives, and what they cost
"Pet-safe" means low mammalian toxicity, not edible. None of these contain metaldehyde.
| Method | Typical cost | How it works | Risk to a cat |
|---|---|---|---|
| Copper tape on pot rims | 8–15 GBP / 10–20 USD per 20 m | Barrier; fails where a leaf bridges it | Very low; a swallowed strip is a foreign body |
| Beer trap, lidded, 2 cm gap | Under 1 USD; one can per two traps | Yeast attracts slugs a short distance | Ethanol is toxic to cats; the lid is not optional |
| Ferric phosphate pellets | 10–20 GBP / 15–25 USD per 685 g–1 kg | Stomach poison for slugs, low mammalian toxicity | Large meals cause vomiting; iron overload can relapse at 12–96 hours |
| Night patrol, torch and bucket | Free | 10 minutes per 10 m of border at dusk | None |
| Bottle cloches over seedlings | Free, from bottles you have | Collar around the stem until it grows | None; smooth the cut edges |
Copper and traps defend pots, not lawns; a whole garden needs ferric phosphate plus night patrol.
If you still use metaldehyde
Outdoor use has been banned in Great Britain since spring 2020 on wildlife and pet grounds; US garden baits at 2% to 4% remain legal. Where it is legal, four habits separate a safe shed from a dead cat.
- Apply at dusk, into a lidded bait station or under a slate, never broadcast on open soil.
- Count what goes out and what comes back; a missing handful is clinic information.
- Keep the cat indoors from dusk to dawn for at least 14 days after application.
- Store the tub in a locked metal bin, never an unlabelled jar, never the shed corner the cat sleeps in.
If it already happened
Carrier, bait box, vomit, phone — fill in the two-copy contact card before you need it. Give the product name, the label percentage and your gram estimate. If tremors start before the car, dim the lights and handle the cat as little as possible; a seizure past 5 minutes is its own emergency, covered in seizure clusters and the first seizure.
Spring gardens hold more than bait: lilies, azaleas and oleander send cats to hospital in April and May (spring garden toxins), and the toxicity checker beats a search engine when the plant is unknown.
This article is general information and does not replace a veterinary diagnosis. Metaldehyde poisoning is time-critical and cannot be assessed from a description: call your vet or a poison control service, and follow their instructions rather than any threshold on this page.
Frequently asked
How much metaldehyde does it take to kill a cat?
The oral LD50 in cats is 207 mg/kg, so a 4 kg cat needs about 828 mg of pure metaldehyde: roughly 41 g of 2% pellets, 21 g of 4% pellets or 14 g of 6% granules. Decontamination is justified far below that at 2 mg/kg, about 0.4 g of 2% bait for the same cat.
Can a cat survive slug pellet poisoning?
Yes, and the prognosis turns on the first 24 hours. Cats that survive that window with treatment usually recover fully, with tremors fading over 24 to 72 hours. One published case needed 28 hours of anaesthesia and went home on day 8 with no residual signs. Liver enzymes still need checking 2 to 3 days later.
Are ferric phosphate pellets safe if my cat eats them?
Safer, not safe. Iron phosphate has very low mammalian toxicity, but a large meal causes vomiting and diarrhoea, and severe iron overload can seem to resolve and then relapse 12 to 96 hours later. Keep the box locked away and phone the vet with the estimated amount.