[header] How to know if your cat ate something toxic [title] Watch for gastrointestinal distress. [step] Excessive vomiting, diarrhea, and frequent urination may all be symptoms of poisoning in cats. Watch closely when your cat goes to the bathroom and listen for sounds of heaving. 
[substeps] A cat may not experience all of these symptoms, depending upon what sort of toxic substance your cat ingested. Do not wait for multiple symptoms to appear.