Why a 5 kg dog reacts strongly to caffeine
A dog this small has far less body mass to process stimulants compared to larger breeds. Caffeine hits their system fast—within 30 minutes you might notice panting or restlessness. The sugar and other ingredients in the energy bar add to the problem by speeding absorption. Even if your pup seems fine now, effects can escalate over the next two hours.
Watch for pacing, whining, or ears twitching at faint sounds. These subtle signs often precede vomiting or muscle tremors. Small dogs are also prone to dangerous spikes in blood pressure from caffeine, which can lead to collapse.
How much caffeine was likely in that half bar
While we can't calculate exact milligrams without lab testing, most energy bars contain 50-100mg caffeine—equivalent to a strong cup of coffee. Your dog consumed enough to potentially exceed their tolerance threshold. The chocolate often paired with caffeine in these bars adds methylxanthines that compound the risk.
Compare this to a 30kg dog eating the same amount: their larger size dilutes the impact. For your 5kg pet, it's like you drinking six espressos back-to-back. The bar's sticky texture also means caffeine lingers in their mouth and digestive tract, prolonging exposure.
Critical signs that mean you need the vet now
Seizures or inability to stand are obvious emergencies, but don't wait for those. If you see rapid blinking, excessive drooling, or gums turning bright red, head to the clinic immediately. These signal cardiovascular strain that home care can't address.
Small dogs deteriorate faster than larger ones once symptoms start. Their hearts may race at over 180 beats per minute (normal is 70-120 for most small breeds). At this size, IV fluids and cardiac monitoring are often needed to prevent organ damage.
What to expect over the next 12 hours
Even with vet treatment, your dog may remain hyperactive for up to a day. The caffeine half-life in canines is about 4.5 hours—much longer than in humans. They'll need a quiet, dark space to recover, away from stairs or sharp objects they might bump into while disoriented.
Post-recovery, watch for lethargy or loss of appetite over the next two days. Some dogs experience rebound hypoglycemia after the caffeine wears off. Keep honey or corn syrup on hand to rub on their gums if they seem weak.
The full verdict, portion guidance and serving notes are collected on the Coffee & caffeine food facts page.