#10: Sudden Extreme Lethargy
A dog that suddenly becomes unusually tired, weak, hard to wake, or uninterested in normal activity may be seriously ill. Some dogs seem confused, barely respond, or struggle to stand or walk. Extreme lethargy can happen with infections, poisoning, heatstroke, pain, or internal medical problems.

Contact a veterinarian promptly, especially if the lethargy appears suddenly or comes with vomiting, breathing trouble, collapse, or refusal to eat. Keep the dog quiet and comfortable while monitoring them closely. If they become unresponsive or cannot stand, seek emergency veterinary care immediately.
