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Scientific research supports the idea that gut health is closely linked to your dog’s behavior. Digestive problems can shape not only your dog’s physical health, but also their emotions and behavior.

Why the Gut Matters for Behavior

The gut microbiome supports digestion, immune function, and the production of mood-regulating chemicals. Changes or imbalances (dysbiosis) can influence your dog’s behavior through the gut–brain axis, affecting neurotransmitter levels and immune function.

Signs That Gut Problems Affect Behavior

Watch for behavioral changes that may signal GI distress, including:

• restlessness, pacing, or agitation due to discomfort or visceral pain;
• lip licking, swallowing, panting (signs of nausea or anxiety) due to reflux;
• hiding, withdrawal, and excessive vocalization, especially if your dog is fearful;
• sudden aggression that is out of character for your dog;
• eating of non-food items (a behavior called pica) such as clothing, their beds, couches, chairs, and toys, or destructive chewing.

These signs can indicate underlying gastrointestinal distress, not merely “bad behavior”.

Gut bacteria regulate neurotransmitters such as serotonin, dopamine, and GABA, which are important to mood and impulse control. Poor gut health can lower levels of these neurotransmitters, resulting in behavior changes consistent with anxiety, irritability, and other abnormal behaviors. Short-chain fatty acids (SCFAs) produced by gut microbes also support brain function; low levels of SCFAs are linked to stress and memory disturbances.

How Inflammation in the Gut Affects Behavior

Gut inflammation releases cytokines, chemical messengers that travel to the brain and trigger “sickness behaviors,” such as lethargy, withdrawal, loss of appetite, depression-like symptoms, aggression, and repetitive behaviors.

Diagnostic Tests to Diagnose Gastrointestinal Disease

If behavioral changes in your dog suggest a gut issue, your veterinarian may use:

• a fecal analysis to screen for parasites, pathogens, signs of inflammation, and measure SCFAs;
• blood work to check for anemia, liver enzymes, inflammation markers (like C-reactive protein, cytokines), and thyroid function (to rule out endocrine causes for aggressive behaviors or anxiety);
• abdominal ultrasound or radiography to visualize GI tract structure, detect obstructions, neoplasia (cancer), or motility problems;
• endoscopy or biopsy to evaluate chronic or severe cases and take tissue samples to diagnose diseases like inflammatory bowel disease (IBD);
• diet trials that are short-term and hypoallergenic or a highly digestible diet, to diagnose food-responsive GI issues;
• urinalysis and advanced tests if urinary or metabolic signs coexist;
• advanced clinics may offer microbiome sequencing to conduct a gut bacteria genetic analysis and evaluate dysbiosis or microbial imbalances.
      

What You Can Do

Keep a log of your dog’s behavioral and digestive changes. Report to your veterinarian:

• unusual restlessness, difficulty sleeping, hiding, or aggressive behavior;
• vomiting, diarrhea, constipation;
• eating strange or non-food items.

Your veterinarian can use your observations and their diagnostic tests to uncover and treat underlying gut disease.

Supporting Your Dog’s Gut Health

• Feed a balanced, fiber-rich diet for healthy bacteria.
• Use probiotics if recommended.
• Avoid abrupt food changes and manage stress for healthier gut-brain signaling.
  
  

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When to Call Your Veterinarian

Always seek veterinary advice if your dog develops new behavioral issues in addition to vomiting, diarrhea, weight loss, lethargy, aggressiveness, or pica. Many sudden behavior problems are early warning signs of treatable medical conditions. Ultimately, understanding the link between gastrointestinal health and behavior can help support your dog’s overall quality of life, and diagnostic tests can assist your veterinarian in identifying hidden medical causes behind changes in behavior.