Diabetic ketoacidosis gives a person's breath a fruity smell that even humans can detect. I haven't researched it, but given that information I wouldn't doubt for a second that a dog can detect more subtle swings.

My dog's behavior would always change when my dad's blood sugar was out of whack. She was a really reliable indicator.

If dogs can smell bombs and drugs even when they are buried, I believe they can smell pretty much any medical issue (if they are trained).

Dogs have been known to sense cancer, diabetes, epileptic seizures, etc. Here is an article that may interest you: [mnn.com]

Also seizure, heart attacks, pregnancy, and other things. Service dogs can be trained to alert the owners and the owners trained to understand.
Fun fact doctors used to test for diabetes by tasting the urine for sweetness.

I was a caregiver and I got a client who had diabetes. To my surprise she had a poodle, it was her personal dog that was by her side that could detect her drop in sugar level. This dog was specifically trained for this. I believe any dog can be trained to recognize and detect a certain disease or any inbalance in a persons body. I had a mixed dog 3 yrs ago he was nothing special never trained for anything except to do tricks for treats. He would lay on my lap and want me to pet him. For 6 months he constantly smelled my one breast. I ignored this thinking it was food he was smelling. It wasn't food, I finally got a mammogram and I had a large lump inside. He passed away after I got better, he too had cancer. So you see I do believe these dogs have way more to offer us than you can every imagine.

I can tell when my blood sugar is too high because my lips taste like strawberries even if I haven't had any. I'm sure that dogs can sense blood sugar changes, they just need trained to know what it means

[google.com] my google fu says yes AND there's actual proof. Dogs super sensitive noses and the particular attention they give their owners combine to make them effective at this it seems.

Low blood sugar has a very distinctive smell. Like fruity liquor.

There are people selling these dogs to kids with t1. Pretty sure they can be trained. Just not exactly sure how they train them to do it. They are also super expensive. It was 60 to 80 grand for a fully trained one. Way to pricey for my ability to pay. Considered trying to teach my dog at one point.

I'm a type 1 diabetic. When I was first diagnosed, more so first found out about a preexisting ailment, I had a lot of dizzy spells and I would pass out. My dog would always hover around around me and lick my face until I came to. I never understood the validity of his actions until I did some research. Turns out, I guess they do have a sense for that, at least to some extent.

Yes they can. There is enough documented evidence now to make the medical profession believe it. There have been cases where doctors have used dogs to assist in diagnosing not just diabetes but other diseases including some cancers.

I know dogs can smell cancer.. I've not heard of diabetes before.

dogs have been known to detect cancer

YES. LOL
And yes, it is natural to some untrained dogs. You can tell when they leave your feet alone when your #s are good, vs when you're out of your Rx.

Not just dogs: [healthline.com]

Um..use google search and you'll find pages of documentation.

Not only dogs can detect physical problems and seizures, but many other pets as well, including parakeets, who fly into their owner's faces and try to get them to lie down, minutes before they have a seizure.

I saw a documentary once, where it was demonstrated that a dog could detect cancer. Diabetes, or rather a problem with their sugar levels, I could see a dog being able to detect that.

While low blood sugar is a problem, isn't sugar that is too high the bigger problem?

I am not going to look up the proofs for you but I do know that there are service dogs to detect many of these health issues for people

That is what studies seems to suggest and that is all I have to go by and studies suggest that dogs can sense a person about to have a seizer.. Take it for what it's worth.

Yes

My mom is diabetic and so are my youngest sister's 2 kids. Mom had a Bassett hound that saved her life and my niece's too

My mom is a type 2...her dog Daisy alerts her. Always accurate so you don't look a gift dog in the mouth!

Yes, and dogs can track the position of commercial planes by sticking their nose in the wind!