If your dog’s blood glucose is high, the most important first step is determining whether it’s a temporary spike or a sign of diabetes. Normal blood glucose in dogs falls between 60 and 120 mg/dL. Most dogs tolerate levels up to about 250 mg/dL without obvious symptoms, and some dogs temporarily hit 400 mg/dL after a meal. But persistent readings above 200 mg/dL mean glucose is spilling into the urine, and your dog needs veterinary evaluation.
Temporary Spikes vs. True Diabetes
Not every high glucose reading means your dog is diabetic. Stress alone can push blood sugar up significantly, which is common during vet visits. Certain medications, particularly steroids, can do the same. A history of pancreatitis also raises the risk of glucose abnormalities. If your dog shows a high reading but has no other symptoms, your vet can run a fructosamine test. This measures average blood sugar over the previous two to three weeks and distinguishes a one-time stress response from genuine, sustained hyperglycemia.
True diabetes, on the other hand, produces a pattern of signs that tends to build gradually. Recognizing those signs early changes the outcome dramatically.
Signs That Point to a Bigger Problem
The classic signs of persistently high blood sugar in dogs are excessive thirst and frequent urination. When glucose stays elevated, the kidneys try to flush it out, pulling extra water with it. Your dog drinks more to compensate, and the cycle continues. You may also notice weight loss even if your dog’s appetite is normal or increased. That happens because the body can’t use glucose properly and starts breaking down fat and muscle for energy instead.
Other signs to watch for include lethargy, weakness, chronic skin infections, and recurring urinary tract infections. In dogs specifically, cloudy eyes from early cataract formation can be one of the first visible changes an owner notices.
When It Becomes an Emergency
If high blood sugar goes untreated long enough, your dog can develop diabetic ketoacidosis (DKA), a life-threatening condition. DKA happens when the body, unable to use glucose, breaks down fat so aggressively that toxic byproducts called ketones build up in the blood.
The warning signs of DKA include vomiting, severe weakness, loss of appetite, and a sweet or fruity smell on your dog’s breath. Severe dehydration follows quickly because excessive urination and vomiting drain fluids faster than your dog can replace them. DKA requires emergency veterinary care. If your dog is vomiting and lethargic on top of drinking and urinating excessively, don’t wait for a regular appointment.
What Your Vet Will Do
Your veterinarian will confirm the diagnosis with blood work and a urinalysis. If diabetes is confirmed, insulin therapy is the primary treatment. Unlike in humans, oral diabetes medications don’t work reliably in dogs, so nearly all diabetic dogs need insulin injections.
The two most commonly prescribed insulin types for dogs are porcine lente insulin (sold as Vetsulin in the U.S.) and NPH insulin. Porcine lente insulin is often the first choice because porcine insulin has the identical amino acid sequence to canine insulin. It produces two peaks of activity, at around 4 hours and 11 hours after injection, and lasts roughly 16 hours. NPH insulin works on a similar timeline. Both are typically given twice daily, timed with meals.
Your vet will start with a conservative dose and adjust it over several weeks based on how your dog responds. The goal is to keep blood sugar between about 80 and 200 mg/dL throughout the day, low enough to prevent symptoms but high enough to avoid dangerous drops.
How to Monitor Blood Sugar at Home
Home monitoring can make a real difference in how well your dog’s diabetes is managed. The standard tool is a blood glucose curve: you measure your dog’s blood sugar every two hours across a full insulin cycle (12 hours if your dog gets insulin twice daily). This reveals how low glucose drops after an injection (the nadir) and how high it climbs before the next dose.
The ideal nadir is between 80 and 150 mg/dL, and the highest reading should stay close to 200 mg/dL. If glucose drops below 150 at any point during the curve, switch to hourly checks to catch any dangerous lows early.
For collecting a small blood sample at home, common sites are the ear margin, a non-weight-bearing footpad, or the elbow callus. A lancet device with adjustable depth works well, or you can use a small hypodermic needle on the ear vein. One important note on equipment: the AlphaTrak 2 glucometer is calibrated specifically for dogs and cats and tends to be the most accurate option. Standard human glucometers are readily available but produce less reliable readings with canine blood, so the veterinary task force on diabetes management recommends against using them.
During a glucose curve, keep everything as normal as possible. Feed your dog the same food at the same time and give insulin on the usual schedule. A disrupted routine makes the results unreliable.
Dietary Changes That Help
Diet works alongside insulin to stabilize your dog’s blood sugar. The general strategy is to slow down how quickly glucose enters the bloodstream after meals. High-fiber, high-protein foods with moderate or low simple carbohydrates accomplish this effectively.
The type of carbohydrate matters as much as the amount. Foods containing pulse ingredients like lentils, chickpeas, and peas tend to have higher levels of resistant starch, a form of starch that resists digestion and gets fermented in the large intestine instead of converting to glucose. Research in dogs has shown that grain-free diets with pulse-based carbohydrate sources produce lower peak glucose and insulin levels after meals, with a slower, more gradual rise compared to grain-based kibbles.
Your vet may recommend a prescription diabetic diet or help you choose a commercial food with the right nutrient profile. Consistency is just as important as composition. Feeding the same amount at the same times each day, coordinated with insulin injections, keeps glucose fluctuations predictable.
What Happens if Glucose Stays High Long-Term
Chronic hyperglycemia causes real damage over time, and in dogs, the eyes are especially vulnerable. Cataracts are the most common complication. About 75% of diabetic dogs develop cataracts within 12 months of diagnosis, regardless of how well blood sugar is controlled. High glucose causes the lens to absorb excess water and become opaque. The cataracts are typically bilateral, affecting both eyes.
Retinopathy, damage to the blood vessels in the back of the eye, can also develop, with a median onset of about 1.4 years after diagnosis. Unlike in humans, where retinopathy often progresses to a more severe proliferative form, dogs generally develop milder, non-proliferative changes. Still, vision loss from cataracts alone can significantly impact your dog’s quality of life, which is one more reason early and consistent glucose management matters.
Beyond the eyes, poorly controlled diabetes increases susceptibility to recurrent infections, contributes to muscle wasting, and raises the ongoing risk of ketoacidosis episodes. Dogs whose blood sugar is well managed with insulin, diet, and regular monitoring can live full, comfortable lives. The adjustment period in the first few weeks to months, while you and your vet find the right insulin dose, is the hardest part. After that, the routine becomes second nature for most owners.