Why a 6 kg Maine Coon is at special risk with spoiled soup
The combination of tomato leaves and bacterial growth from sitting overnight makes this far worse than fresh leaves alone. Solanine and tomatine concentrations don't degrade with spoilage, but the soup's liquid form means your cat ingested every drop of those dissolved toxins. At 6 kg, your Maine Coon's body weight puts them in the danger zone where even small amounts can trigger severe reactions.
Watch for retching or excessive lip-licking in the next hour — these are early signs the alkaloids are irritating the stomach lining. The spoiled food adds a separate risk of bacterial toxins causing fever or diarrhoea within 4-6 hours. Don't wait for multiple symptoms; one episode of vomiting plus any drooling means the toxins are circulating.
How tomato leaf poisoning progresses in cats
Unlike dogs, cats often show neurological signs first — a wobbly walk or sudden reluctance to jump up on surfaces they normally can. The 6 kg body size means these signs can appear within 90 minutes if enough solanine was in those leaves. Vomiting may seem to 'help' at first, but it doesn't remove all the absorbed toxins.
Check the gums — if they're paler than usual or feel tacky, the vomiting has already caused dehydration. Tomato leaf poisoning rarely causes seizures in cats, but muscle tremors or exaggerated swallowing motions are red flags that the nervous system is affected. Time matters more than dosage here.
Why you shouldn't try home treatment
Inducing vomiting isn't safe with possible neurological symptoms developing, and water won't dilute these fat-soluble toxins. The spoiled food component means antibiotics might be needed, but only a vet can determine that after blood work. Even if your cat seems fine now, solanine can cause delayed heart rhythm changes in felines.
Gather details for the vet: roughly how many leaves were in the soup pot, whether your cat ate mostly liquid or chunks, and any changes in litter box habits today. These help determine whether to use IV fluids or just monitoring. Don't offer food — fasting gives the gut a chance to recover from the double insult of plant toxins and bacteria.
When to bypass the vet call for direct ER care
If those leaves were from green tomatoes (not ripe ones), the solanine content could be 3-5 times higher. Any head-shaking or pawing at the mouth suggests oral irritation worsening. For a cat this size, two vomiting episodes in an hour or refusal to drink warrants immediate transport.
Keep the cat in a dim, quiet space while arranging care — neurological toxins make them sensitive to light and sound. Bring a sample of the vomit if possible; greenish tinges indicate higher solanine exposure. The ER team will likely check potassium levels first, as imbalances from tomato toxins can affect the heart rapidly in cats.
The full verdict, portion guidance and serving notes are collected on the Tomato leaves & stems food facts page.