Why is it risky?
Coffee, tea, and other caffeinated beverages contain caffeine, a methylxanthine that cats cannot metabolize effectively. Caffeine inhibits phosphodiesterase, elevates cyclic AMP, and stimulates the CNS and cardiovascular system. It shares this mechanism with theobromine (the toxic compound in chocolate). Cats are significantly more sensitive to methylxanthines than humans due to slower hepatic clearance.
Affected Systems
Nervous · Cardiovascular
Symptoms
Restlessness, hyperactivity, rapid breathing, elevated heart rate, cardiac arrhythmias, muscle tremors, hyperthermia, seizures.
What To Do
Contact vet or poison control immediately. No safe home treatment. Vet may induce vomiting if ingestion was recent. Cardiac monitoring and supportive care may be required.
Notes
Applies to: espresso, filter coffee, black tea, green tea, energy drinks, cola, caffeinated protein shakes. Decaffeinated coffee still contains residual caffeine, it is not safe. Tea bags and coffee grounds are more concentrated than brewed beverages and represent higher risk. Matcha is particularly high in caffeine relative to its volume.
Sources
→ ASPCA Animal Poison Control Center — aspca.org
→ Merck Veterinary Manual