Dogs with untreated diabetes often drink at least two to three times more water than normal. This happens because high sugar levels in the blood spill into the urine, pulling extra fluid with it and making dogs unusually thirsty.
There are several changes you may have noticed in your dog’s behaviours and appearance that are caused by having high blood glucose levels and starving cells that can’t access that glucose. These include:
When fat cells don’t have access to glucose, they start breaking down stored fat into fatty acids for energy. This can lead to rapid weight loss even if your dog is eating normally or even more than usual.
When your dog’s cells are starving for energy, their body responds by releasing hormones and other chemicals that make them feel hungry so you may notice them begging for food a lot or finishing their meals very quickly. Giving them more food will only make the problem worse because they are taking in even more glucose with nowhere to put it.
When the body starts breaking down fat for energy, it produces chemicals called ketones, one of which is acetone. These ketones can make your dog’s breath smell sweet or fruity, which is a sign that their body is struggling to use glucose properly and is breaking down fat too quickly.
The body has a back-up system that can help get rid of extra glucose. When blood glucose levels get above 180 to 200 mg/dL (10 to 11 mmol/L), the kidney will let glucose escape into the urine. This makes the urine more concentrated, which pulls water from the blood to help get rid of the sugar. As a result, your dog may pee more often and in larger amounts. You might notice them asking to go outside more frequently or having accidents inside the house.
Because your dog is peeing so much to get rid of the extra glucose, they start to lose a lot of water from their body. This makes them feel thirsty, so they drink much more than usual to try to stay hydrated. You might notice them at their water bowl more often or find yourself refilling it much more frequently.
Dogs have an enzyme inside the lens of their eyes that can turn extra glucose into other substances. When blood glucose stays too high for too long, these substances build up and draw water into the lens, making it swell and turn cloudy. This can lead to cataracts and vision problems.
The most serious complication of diabetes is something called diabetic ketoacidosis (DKA). This can happen if your dog suddenly needs a lot more energy than usual—such as after very intense exercise or if they become sick with another illness like pancreatitis, urinary tract infections, or Cushing’s disease. In response, the body begins rapidly breaking down fat, flooding the bloodstream with fatty acids. The liver turns these fatty acids into ketones as a backup fuel source. But without enough insulin to slow this process down, ketones can quickly build up to dangerous levels, making the blood much more acidic than normal. This shift in blood acidity can make your dog very sick — causing vomiting, weakness, rapid breathing, dehydration, and, if not treated quickly, it can lead to coma or even death.
If left untreated, diabetes will keep making your dog feel worse over time and can seriously affect their quality of life.
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