When you notice your old dog eating grass and not eating their regular food, it can raise understandable concern.
This behavior might seem harmless at first glance, but when a senior dog suddenly prefers grazing on grass and shows little to no interest in food, it may indicate a deeper issue.
We outline what it means when an old dog is eating grass and not eating their meals, the possible causes behind it, and what actions to take to help them feel better.
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Old Dog Eating Grass and Not Eating: What It Means
When an old dog is eating grass and not eating their regular food, it’s often a sign of an underlying issue such as gastrointestinal upset, dental problems, kidney or liver disease, diet intolerance, cognitive dysfunction, nutritional deficiency, parasites, or emotional stress.
These conditions can lead to nausea, discomfort, or behavioral changes, prompting the dog to seek relief by eating grass while avoiding their usual meals.
Identifying the root cause is key to ensuring your senior dog’s health and well-being.
Old Dog Eating Grass and Not Eating: Common Causes
1. Gastrointestinal upset
One of the most common reasons for an old dog eating grass and not eating is an upset stomach.
Grass acts as a natural emetic—meaning dogs may eat it to trigger vomiting.
This is often their way of relieving nausea or clearing something irritating from their digestive tract.
Older dogs are especially prone to gastrointestinal issues like gastritis, inflammatory bowel disease (IBD), or even pancreatitis.
These conditions can cause nausea, vomiting, and a loss of appetite.
If your senior dog is repeatedly eating grass and skipping meals, it’s a good idea to monitor for other signs such as drooling, gulping, or licking their lips—signs of nausea.
2. Dental problems
As dogs age, dental health becomes a major concern. Tooth decay, gum disease, and oral infections can make eating painful.
When your old dog is eating grass and not eating kibble or soft food, it could be because chewing is uncomfortable or even painful.
Grass, though fibrous, may be easier to nibble than hard kibble. If your dog avoids their usual food but nibbles grass, check their mouth for signs of swelling, redness, or bad breath.
Dental pain can severely impact a dog’s appetite and needs prompt veterinary attention.
Related: Dog eating grass and not eating (Here’s why)
3. Kidney or liver disease
Senior dogs are more likely to suffer from organ dysfunction, particularly involving the kidneys and liver.
When a dog’s kidneys or liver aren’t functioning properly, toxins can build up in the body, leading to nausea and reduced appetite.
Old dog eating grass and not eating food could be a subtle sign of kidney failure or liver disease.
These conditions often present with other symptoms such as weight loss, vomiting, lethargy, or increased thirst and urination.
A blood test can help confirm any underlying organ issues.
4. Diet intolerance or food aversion
As dogs grow older, their digestive systems become more sensitive.
What they used to eat comfortably may now cause gastrointestinal upset.
If your dog recently changed diets, or if the food formula has changed, your old dog may be eating grass and not eating their food due to stomach discomfort or a newfound aversion to the current food.
Even long-term foods can become problematic due to aging digestive systems.
Grass-eating could be your dog’s way of managing the resulting queasiness.
Try offering a bland diet temporarily—like boiled chicken and rice—and see if that improves their appetite.
5. Cognitive dysfunction or behavioral issues
Cognitive decline in older dogs, often referred to as canine cognitive dysfunction (similar to dementia in humans), can cause unusual behavior patterns, including changes in appetite and odd eating habits like grass consumption.
An old dog eating grass and not eating meals may be showing signs of confusion, anxiety, or memory problems.
They might forget their routine or lose interest in things they used to enjoy, including food.
Other signs of cognitive decline include pacing, staring at walls, or disrupted sleep patterns.
Related: Dog Eating Grass and Not Eating and Vomiting (Explained)
6. Nutritional deficiency
Another possible explanation for an old dog eating grass and not eating food is a nutritional deficiency.
Although commercial dog food is generally balanced, aging dogs may absorb nutrients differently or require more specific vitamins and minerals.
Some theories suggest dogs may instinctively seek grass to compensate for fiber or micronutrient imbalances.
While this isn’t proven, ensuring your senior dog’s diet is complete and appropriate for their age can help prevent nutritional-related behaviors.
7. Parasites or internal infections
Even older dogs can suffer from intestinal parasites or infections that affect their digestive tract.
Parasites like roundworms or hookworms may lead to stomach discomfort, appetite loss, and grass eating.
These internal issues may not be immediately obvious, especially in senior dogs with weakened immune systems.
Regular fecal exams and deworming schedules can help rule out this cause.
8. Stress and emotional changes
Senior dogs can be more emotionally sensitive, especially when exposed to stressors like household changes, a new pet, travel, or loud noises.
If your old dog is eating grass and not eating food, they may be experiencing anxiety.
Stress can manifest as gastrointestinal upset and altered eating behavior.
Some dogs turn to grass as a coping mechanism, similar to how humans fidget or bite their nails.
Behavioral stress can also trigger temporary anorexia, especially in aging dogs that are less adaptable.
What to do if your old dog is eating grass and not eating
If your old dog continues eating grass and avoids their regular meals, don’t ignore it.
Occasional grass nibbling is normal, but persistent grass-eating combined with appetite loss is a red flag. Here’s what to do:
1. Monitor closely for other symptoms
Watch for vomiting, diarrhea, lethargy, bloating, excessive drooling, bad breath, or sudden weight loss.
These signs can help your vet determine what’s going wrong.
2. Examine their mouth
Check for swollen gums, broken teeth, or signs of dental pain.
If your dog winces when you touch their mouth, they likely have a dental issue.
3. Offer a bland diet
Try feeding a bland, easy-to-digest meal like boiled chicken and rice for 1–2 days.
If they eat this willingly, the issue may be related to their regular food.
4. Avoid letting them graze unsupervised
Eating too much grass can irritate their stomach and even cause vomiting.
Supervise them outside to limit access to treated lawns or pesticide-exposed grass.
5. Visit your veterinarian
Persistent grass-eating and appetite loss in older dogs should be evaluated by a vet.
Bloodwork, fecal exams, and imaging can uncover kidney disease, infections, or other health conditions.
6. Evaluate their diet
Ensure your senior dog is eating food specifically formulated for older dogs.
Consider switching to a prescription or vet-recommended senior diet that supports digestion, joint health, and organ function.
7. Address stress and cognitive health
If your vet rules out physical illness, consider whether emotional stress or cognitive decline is playing a role.
Provide a stable routine, mental stimulation, and comforting surroundings.
In some cases, your vet may recommend anxiety-relief medications or supplements.
When to seek urgent help
While not all cases require emergency care, contact your vet immediately if your old dog eating grass and not eating also shows any of the following:
Vomiting or diarrhea lasting more than 24 hours
Blood in stool or vomit
Sudden collapse or extreme lethargy
Refusal to eat for more than 48 hours
Signs of abdominal pain or bloating
Suspected poisoning from treated grass or garden chemicals
Older dogs are less resilient to dehydration and nutrient loss, so early intervention is critical.
Key Takeaway
An old dog eating grass and not eating food is more than just quirky behavior—it can signal discomfort, nausea, dental issues, emotional distress, or serious medical problems.
While occasional grass nibbling is common, persistent eating of grass with a lack of appetite should prompt closer observation and a veterinary check-up.
By recognizing the signs early and addressing the underlying cause—whether it’s a dietary issue, illness, or stress—you can help your senior dog stay healthy and comfortable in their golden years.