When your dog is drinking lots of water suddenly and not eating, it’s natural to be concerned. Sudden changes in your dog’s thirst and appetite can be alarming and may indicate an underlying health problem.
While some dogs may simply have an off day, it’s important to monitor the situation closely—especially if these symptoms persist or are accompanied by other unusual behaviors.
We outline what might cause your dog to drink excessively while refusing food, what signs to watch for, and when you should take action.
Dog drinking lots of water suddenly and not eating: why it happens
A dog drinking lots of water suddenly and not eating can be caused by several underlying issues that impact hydration, appetite, or both.
Common causes include kidney disease, diabetes mellitus, gastrointestinal upset, infections, medications, dehydration or hot weather, stress or anxiety, toxin exposure, hormonal disorders like Cushing’s disease, and age-related organ decline.
These conditions may disrupt the dog’s internal balance, leading to excessive thirst as the body attempts to compensate for fluid loss or systemic stress, while appetite decreases due to nausea, discomfort, or metabolic changes.
Dog Drinking Lots of Water Suddenly and Not Eating: Common Causes
1. Kidney disease
One of the most common reasons for a dog drinking lots of water suddenly and not eating is kidney disease.
The kidneys play a key role in filtering toxins from the blood and regulating hydration.
When kidney function is impaired—due to aging, genetics, infection, or exposure to toxins—the dog’s body can’t retain water effectively.
This leads to excessive thirst as the body attempts to flush out waste.
The buildup of toxins may also make your dog feel nauseated, leading to loss of appetite.
Other signs of kidney disease may include vomiting, weight loss, bad breath, and increased urination.
2. Diabetes mellitus
Another major cause of a dog drinking lots of water suddenly and not eating is diabetes.
This disease interferes with the body’s ability to process sugar, resulting in increased thirst and appetite changes.
While early diabetes may be marked by a ravenous appetite, advanced or unmanaged diabetes can cause dogs to feel weak, nauseous, or lethargic—leading them to stop eating.
The excess sugar in the bloodstream pulls water from tissues, leading to increased water consumption.
Look out for signs such as frequent urination, sweet-smelling breath, cloudy eyes, and weight loss despite drinking and eating changes.
Related: Dog drinking a lot of water and not eating (Causes and when to worry)
3. Gastrointestinal upset
Sometimes, a dog drinking lots of water suddenly and not eating is simply reacting to stomach upset.
Just like humans, dogs can have indigestion from eating something they shouldn’t—like garbage, spoiled food, or a sudden change in diet.
Upset stomachs may cause nausea, making your dog avoid food. At the same time, they may drink more water to try to soothe their discomfort or stay hydrated.
This situation often resolves within 24–48 hours, but if your dog continues refusing food or starts vomiting or having diarrhea, veterinary care is needed.
4. Infections
Bacterial or viral infections can cause systemic effects in dogs, leading to increased water intake and appetite suppression.
Infections like leptospirosis, canine parvovirus, or pyelonephritis (kidney infection) can all result in a dog drinking lots of water suddenly and not eating.
The infection may cause fever, nausea, or general discomfort, which can explain both the excessive thirst and refusal to eat.
These illnesses are often accompanied by other symptoms such as vomiting, diarrhea, lethargy, and changes in urination.
Prompt diagnosis and treatment are essential to avoid complications or worsening symptoms.
5. Medications
Certain medications can trigger increased thirst and appetite changes. For example, corticosteroids such as prednisone are known to cause a dog to drink more water than usual.
At the same time, some medications may cause nausea or digestive upset, making your dog reluctant to eat.
If your dog has recently started a new medication and is now drinking lots of water suddenly and not eating, consult your veterinarian to assess whether the medication is responsible.
6. Dehydration or hot weather
A dog may also drink excessively if they are dehydrated or overheated.
Hot weather or increased physical activity can cause fluid loss, prompting your dog to drink more water.
If your dog feels mildly unwell or has a minor electrolyte imbalance, they might not feel like eating.
While this may be temporary and resolve quickly, keep an eye on other symptoms like heavy panting, lethargy, or sunken eyes.
Dogs can easily become dehydrated without obvious signs, especially if they aren’t eating.
Related: Old dog drinking lots of water suddenly and not eating (Explained)
7. Stress or anxiety
Stress can also explain why a dog is drinking lots of water suddenly and not eating.
Major changes like moving to a new home, introducing new pets, loud noises (such as fireworks), or separation anxiety can affect your dog’s emotional state.
Stress often leads to reduced appetite in dogs.
Meanwhile, some stressed dogs may drink more water as a coping behavior or because of dry mouth caused by panting or increased respiration.
Signs of stress may include pacing, hiding, whining, drooling, or restlessness.
8. Toxin exposure or poisoning
If a dog drinks lots of water suddenly and stops eating, it may be a response to toxin exposure.
Some substances—such as antifreeze, chocolate, human medications, or contaminated food—can damage organs, cause vomiting, and trigger dehydration, leading to increased thirst.
Ingesting toxins can be life-threatening. Other signs of poisoning may include drooling, vomiting, seizures, uncoordinated movements, and collapse.
If you suspect poisoning, seek emergency veterinary care immediately.
9. Hormonal disorders
Cushing’s disease (hyperadrenocorticism) occurs when the adrenal glands produce too much cortisol.
This can lead to a dog drinking lots of water suddenly, while also exhibiting a reduced appetite.
Dogs with Cushing’s may also show symptoms like a pot-bellied appearance, hair thinning, muscle weakness, or frequent urination.
The condition is more common in middle-aged to older dogs and requires blood tests for diagnosis.
10. Aging and organ decline
As dogs get older, their organs naturally begin to decline in function.
Senior dogs may experience reduced appetite, changes in thirst, or early stages of kidney, liver, or endocrine diseases.
An older dog drinking lots of water suddenly and not eating could be showing signs of an age-related condition that requires medical attention.
Regular checkups and bloodwork are important for senior dogs to catch issues early.
What to do
If your dog is drinking a lot of water suddenly and not eating, take the following steps:
1. Monitor for other symptoms
Check for vomiting, diarrhea, lethargy, changes in urination, panting, or bloating.
These signs can help determine how urgent the situation is.
2. Check for recent changes
Have you recently changed your dog’s diet? Started a new medication?
Introduced new stressors? Identifying a potential trigger can help narrow down the cause.
3. Avoid offering too many treats
Sometimes dogs skip meals if they’ve been filling up on treats.
Stick to a consistent feeding schedule and avoid giving treats until their regular appetite returns.
4. Ensure fresh water is always available
Hydration is critical. Make sure your dog has access to clean, fresh water at all times.
5. Don’t wait too long
If your dog refuses food for more than 24 hours or if excessive drinking continues for over a day, consult your veterinarian.
Dogs can quickly develop complications from not eating or from underlying conditions causing excessive thirst.
6. Seek emergency care if needed
Contact your vet immediately if you notice any of the following:
Vomiting or diarrhea with blood
Signs of pain or bloating
Seizures or collapse
Gums that are pale or gray
Signs of poisoning or ingestion of toxic substances
Key Takeaway
A dog drinking lots of water suddenly and not eating may be experiencing anything from mild digestive upset to a serious underlying condition.
While occasional off-days happen, prolonged symptoms, rapid changes in thirst or appetite, or accompanying warning signs deserve prompt veterinary attention.
Early intervention is key. Whether the cause is stress, infection, kidney issues, or something else, identifying and treating the problem early helps prevent complications and ensures your dog stays happy and healthy.
Always trust your instincts—if your dog’s behavior seems off, don’t hesitate to seek professional help.