The “Dawn Phenomenon”: Why your diabetic dog’s blood sugar can spike before breakfast.

We would see great blood glucose readings with our diabetic border terrier Parker – he’d go to bed at a normal level – and then the next morning his levels would be high.

After some digging, we learned there’s a name for it: the dawn phenomenon. When I first heard it, I thought it was “Don” phenomenon because so many conditions are named after scientists, researchers or the animals who had them. But this one is logically named.

What Is the Dawn Phenomenon?

The dawn phenomenon refers to a natural rise in blood sugar that happens in the early morning hours — usually between 4 a.m. and 8 a.m. 

It’s typically driven by a dog’s internal clock. As a dog’s body prepares to “wake up,” hormones like cortisol, growth hormone, and catecholamines are released. These hormones tell the liver to send more glucose into the bloodstream to provide energy for the day ahead.

In non-diabetic dogs, the pancreas releases extra insulin at the same time, keeping blood sugar levels in check. But in our diabetic dogs, where insulin must be given by injection, this balancing act doesn’t happen naturally. 

The result is that blood sugar may spike in the morning despite good control overnight.

Well isn’t that frustrating?

Why does it matter?

Morning highs can make it seem like your dog’s insulin isn’t working properly, when it seems that this is a predictable — and normal — hormonal event. Recognizing the dawn phenomenon is important, because it affects how your vet interprets glucose curves and adjusts insulin doses.

Some clues that your dog may be experiencing the dawn phenomenon include:

• Morning glucose readings are consistently higher than at other times of day.
• Blood sugars are well controlled overnight but rise before breakfast.
• A glucose curve shows a steady climb toward the end of the dosing cycle.

What you can do

If you notice morning highs, don’t panic — and don’t change insulin doses on your own. Instead:

• Track your dog’s glucose carefully, especially at bedtime, overnight (if possible), and first thing in the morning. We would run a glucose curve with a reading late at night, and then again at 4am, 6am and 8am (we feed Parker at 8:30)
• Share these patterns with your veterinarian. They will determine if the dawn phenomenon is the cause, or if something else (like the Somogyi effect, a rebound rise after a low blood sugar episode) may be happening.
• Follow your vet’s guidance — they may suggest adjusting the timing, type, or dose of insulin to help smooth out the morning spike.

Pay attention to any late night treats

A diabetic dog should get low-fat, no-carb treats away from their mealtimes, so make sure any evening or late night snacks don’t contain sugars or ingredients that could spike your diabetic dog’s blood glucose. There are some surprising products out there like Pill Pockets and peanut butters that could be problematic.

What we learned

The dawn phenomenon is your dog’s body giving a “wake-up call” by releasing hormones that increase blood sugar. For diabetic dogs, it can cause frustrating morning spikes — but with careful monitoring and veterinary guidance, it can be managed effectively.

If you’re seeing higher numbers in the morning, talk with your vet. Together, you can keep your dog’s diabetes under control and help them enjoy a healthier, happier life.