Pinpointing the underlying cause of decreased appetite (inappetence) in a pet is crucial for proper treatment. The first step is determining whether the issue is medical or non-medical.
Non-medical causes are often linked to stress or anxiety. Life changes such as moving, the addition of a new family member or the loss of a companion can cause pets to lose interest in food and become withdrawn. These symptoms are typically temporary and resolve once the pet adjusts.

Medical causes, however, are more common and can range from localized issues to systemic diseases. Oral problems like severe periodontal disease, infections or tumors can make it difficult for pets to chew or swallow food. But more serious health conditions and disease can also lead to decreased appetite and lethargy.

A thorough history and physical examination are essential for diagnosis. A veterinarian will ask about changes in drinking, urination and bowel habits, plus the duration and severity of symptoms. A physical exam may reveal warning signs such as abnormal heart sounds, abdominal masses, or pale gums, which could point to more serious conditions. Often, diagnostic tests are needed.

A Complete Blood Count (CBC) provides information about blood cells, helping to identify anemia, infection or bone marrow disorders, and can also signal systemic diseases like leukemia or immune-mediated conditions.

Serum biochemistry analyzes the liquid part of blood (serum) and provides insights into the health of various organs. In pets with decreased appetite and listlessness, serum biochemistry can reveal kidney disease (elevated urea and creatinine), diabetes (elevated glucose), liver failure (decreased glucose, albumin and urea) or liver damage (increased liver enzymes).

A urinalysis helps evaluate kidney function, inflammation, infection, and metabolic disorders. In pets that are listless and not eating, urinalysis can detect kidney disease, bladder infections, or cancer in the urinary system.

Additional tests may include serum thyroxine for hypothyroidism, pancreatic-specific lipase for pancreatitis and ACTH stimulation for Addison’s disease. X-rays or ultrasounds may be used to evaluate organs or check for cancer, and bacterial cultures can detect infections.
Having a good relationship with a veterinarian—one that provides thorough, step-by-step evaluations with detailed explanations—is key to ensuring that pet owners embark on the best course of action that takes into account both the needs of the pet as well as any financial considerations.