If your dog is suddenly drinking more water and gaining weight, it might seem like they’re just thriving—but these changes can sometimes signal a deeper issue. While occasional thirst or weight fluctuation can be normal, the combination may point to hormonal or metabolic disorders.
We outline the common causes of dog drinking a lot of water and gaining weight, what you can do at home, and when to seek veterinary help.
Dog Drinking a Lot of Water and Gaining Weight — Why It Happens
Excessive drinking and weight gain in dogs can result from Cushing’s disease, hypothyroidism, medication side effects, poor diet, or lack of exercise. While some causes are manageable lifestyle issues, others require blood tests and long-term veterinary treatment.
Common Causes of Dog Drinking a Lot of Water and Gaining Weight
Cushing’s Disease (Hyperadrenocorticism)
Cushing’s is a hormonal disorder caused by excess cortisol production.
It commonly leads to increased thirst, frequent urination, panting, and gradual weight gain—especially around the belly.
Other signs include thinning fur, fragile skin, and muscle loss. Diagnosis requires bloodwork and sometimes ultrasound.
Hypothyroidism
Underactive thyroid function slows down metabolism, often resulting in weight gain despite normal or reduced appetite.
Affected dogs may also drink more, appear sluggish, or have dry skin and a dull coat.
This condition is confirmed via thyroid hormone testing and is managed with daily medication.
Poor Diet and Overfeeding
Some dogs gain weight simply from overeating or consuming high-calorie food and treats.
Dietary excess can also cause increased thirst, especially if food is high in sodium.
Portion control and switching to a well-balanced weight management formula can help.
Read more: Dog Drinking a Lot of Water and Panting (What this reveals)
Lack of Exercise
Inactivity due to age, arthritis, or lifestyle changes can lead to both weight gain and increased thirst.
Dogs who don’t get regular walks or playtime often become lethargic and may drink more out of boredom.
Adding structured daily activity supports both physical and mental health.
Medication Side Effects
Steroids and some anti-seizure medications can cause increased appetite, thirst, and weight gain.
If your dog has recently started new medication, monitor for these side effects.
Consult your vet about possible alternatives or dosage adjustments if the symptoms become concerning.
What to Do If Your Dog Is Drinking More and Gaining Weight
Track your dog’s weight regularly and monitor water intake over several days.
Ensure your dog is eating a high-quality, portion-controlled diet suitable for their size and age.
Encourage daily exercise appropriate for your dog’s health and mobility.
Avoid over-treating or offering human food that may contribute to both symptoms.
Schedule a veterinary checkup to screen for endocrine disorders or medication side effects.
When to Call or Visit Your Vet
Contact your vet if your dog:
Has unexplained weight gain over weeks or months
Drinks more than usual for multiple days
Shows signs of lethargy, coat changes, or skin issues
Is on steroids or other medications and has developed these symptoms
Seems bloated, panting excessively, or has changes in urination
Bloodwork and hormone testing can help identify treatable conditions like Cushing’s or hypothyroidism.
Read more: Dog Drinking a Lot of Water and Diarrhea (Is it something serious?)
Key Takeaway
If your dog is drinking a lot of water and gaining weight, it may not just be lifestyle—it could signal a medical condition like hypothyroidism or Cushing’s disease.
Stay alert, monitor symptoms, and consult your vet early to catch problems before they worsen. Timely diagnosis helps keep your dog healthy and comfortable.