Heat stroke
What is heat stroke?
Heat stroke occurs when the body cannot lose heat quickly enough and the internal temperature rises to a level that damages tissues. It is more than simply being hot: severe heat-related illness can affect the brain, circulation, lungs, gastrointestinal tract, kidneys and the body’s ability to clot blood.
A pet may cool down before arriving at hospital but still have significant internal injury. Complications can develop or worsen over the following hours to days, so veterinary assessment is essential.
How does it happen?
Heat stroke may occur after:
• Exercise or strenuous play in warm or humid conditions
• Being left in a parked vehicle, enclosed space or poorly ventilated area
• Being outdoors without adequate shade, airflow or water
• Prolonged seizures, severe breathing difficulty or other illnesses that generate excessive body heat
Dogs are affected most often, but cats and other pets can also develop heat-related illness. It can occur even on days that do not seem extremely hot, particularly during exercise or when humidity is high.
Which pets are at greater risk?
• Brachycephalic (short-nosed) breeds
• Overweight, elderly, very young or poorly conditioned pets
• Pets with airway, heart or lung disease
• Dogs with thick coats or limited heat acclimatisation
• Pets with a previous episode of heat-related illness
Signs of heat stroke
• Heavy or persistent panting and excessive drooling
• Restlessness, distress or seeking cool surfaces
• Bright red, pale, blue-grey or purple gums
• Vomiting or diarrhoea, which may contain blood
• Weakness, wobbliness, confusion or collapse
• Muscle tremors, seizures or reduced responsiveness
• Rapid or difficult breathing
• Bruising, pinpoint red spots or other signs of abnormal bleeding
Important: The severity of heat stroke cannot be judged by body temperature alone. A pet with a normal temperature after cooling may still be critically unwell.
What should I do immediately?
Cool first, then transport. Start cooling while arranging immediate travel to the nearest veterinary hospital.
• Move your pet out of the hot environment and into shade or air conditioning.
• Wet the body continuously with cool or cold tap water and create airflow with a fan, open windows or air conditioning.
• For a conscious dog that can safely stand and hold its head up, immersion in cool or cold water can provide rapid cooling. Do not immerse an unconscious, seizing, vomiting or breathing-compromised pet.
• Transport your pet immediately and continue cooling during travel where practical.
Do not wrap your pet in wet towels, as they can trap heat. Do not force water into the mouth, apply alcohol to the paws, or delay travel while repeatedly checking the temperature.
You may offer a small amount of cool water only if your pet is fully alert and able to swallow normally.
What happens at the veterinary hospital?
Treatment is tailored to the severity of illness and the organs affected. Your pet may initially appear stable but require close monitoring because complications can be delayed.
• Controlled cooling and continuous temperature monitoring
• Oxygen therapy and support of breathing and circulation
• Intravenous fluid therapy, adjusted to the individual patient
• Blood tests to assess blood cells, glucose, electrolytes, kidney and liver function
• Clotting tests and repeated monitoring for abnormal clotting or bleeding
• Urine testing, blood pressure and heart rhythm monitoring
• Medication for seizures, nausea, gastrointestinal injury or pain when required
• Plasma or blood transfusion if significant bleeding or clotting abnormalities develop
• Advanced organ support or intensive care in severely affected patients
What is the outlook?
Outcome depends on how high the body temperature became, how long it remained elevated, the cause of overheating and the degree of organ injury. Rapid cooling before arrival and prompt veterinary treatment improve the chance of survival.
Pets with collapse, persistent neurological abnormalities, low blood glucose, kidney injury, abnormal clotting or significant bleeding have a more guarded prognosis. Even after apparent improvement, hospitalisation and repeat testing may be recommended because deterioration can occur over the next 24-72 hours.
Preventing heat stroke
• Never leave a pet unattended in a parked vehicle, even with windows open or on a mild day.
• Exercise during the coolest part of the day and reduce intensity in warm or humid weather.
• Provide shade, ventilation and multiple sources of fresh water.
• Ensure outdoor enclosures for pocket pets and poultry, including guinea pigs and chickens, remain fully shaded and well ventilated throughout the day, as direct sun can quickly make hutches and coops dangerously hot.
• Use extra caution with high-risk pets and stop activity at the first sign of excessive panting, slowing down or distress.
• Avoid muzzles or equipment that restricts panting during exercise unless specifically required for safety and closely supervised.
Clinically reviewed and approved by Dr Giulia Agostini, Pet Emergency Senior Veterinarian and Clinical Manager, DVM MANZCVS (ECC) August 2026