Lethargy

Lethargy is a state of reduced energy, alertness, and activity, seen in an animal as unusual sleepiness, reluctance to move, or lack of interest in normal routines.

The sign is nonspecific and accompanies many conditions, from minor infections and pain to serious illness such as anemia, organ disease, or poisoning. Owners typically notice that a dog or cat sleeps more, responds slowly, declines walks or play, or seems dull. Veterinarians assess lethargy by history, physical examination, and often blood work, because the cause is rarely obvious from the sign alone. A sudden onset is treated more urgently than a gradual change in an older animal.

Lethargy is one of the most frequently reported signs when pets are accidentally exposed to THC-containing cannabis, often together with ataxia, dilated pupils, and urinary dribbling, and it has been recorded as a tolerability observation in some canine cannabinoid studies. Because the same sign can point to unrelated and serious problems, a lethargic animal warrants a veterinary visit. Owners are encouraged to tell the veterinarian about any substances the animal could have reached, including cannabis or hemp products.