Slash the chocolate Lab jumped into Kate Rondelli’s bed in the middle of the night Tuesday, licking her face to wake her up.

There was trouble.

The dog led her to her son’s room, where Rondelli tested her 4-year-old’s blood sugar levels: Over 400 milligrams per deciliter, more than twice the maximum range desirable for the little boy with Type 1 diabetes.

Rondelli quickly gave her son, Mylon, insulin to stabilize his levels, averting a possible medical emergency.

“His nose is always working,” Rondelli said.

Slash is a diabetes detection dog, trained to alert Rondelli when her son’s blood sugar falls or spikes to potentially dangerous levels. The dog and his new family visited the Bunker Hill Fire Station in Prince George’s County, Maryland, on Wednesday to get acquainted with first responders as part of Slash’s training.

Service dogs can be protective of their owners, so Rondelli and Slash’s trainers wanted to make sure that if firefighters have to be called to the house for a medical emergency, Slash would be familiar with people in uniform and stand down to let medics treat Mylon.

The dog visited the firehouse in Brentwood twice so that “when we show up for a call, not only Mylon but Slash is familiar with us being there and us being in close contact with Mylon,” said James Key, acting battalion chief for the Prince George’s County Fire Department. “The first time Slash will meet us is not when we come with lights and sirens.”

Erin Gray, with the organization that trained Slash, said diabetes dogs, like bomb-sniffing or drug-sniffing dogs, are trained to detect smells as a way to alert people to trouble.

In Slash’s case, he was taught to detect acetone scents coming from Mylon’s body as a signal of low blood sugar and sweet, syrupy smells as an indication of high blood sugar.

“He gets rewarded when Mylon is out of range,” said Gray, a trainer with Service Dogs by Warren Retrievers based in Virginia.

Dogs like Slash go through an extensive training and obedience program for nine to 18 months before they are delivered to families, Gray said. After that, each dog is customized to the needs of the person they serve.

Mylon was diagnosed with Type I diabetes two years ago, when Rondelli noticed her son was constantly thirsty and quickly wetting diapers.

She took him to the doctor, where they discovered his blood-sugar levels were through the roof. Mylon immediately was sent to a children’s hospital, where he spent four days in intensive care.

People with Type I diabetes do not have a pancreas functioning normally to produce insulin to regulate the body’s blood sugar. Levels that are too high can damage nerves and blood vessels. Levels that are too low can trigger seizures, fainting or a coma.

Slash has been with the family only since Monday, but he has already sensed Mylon’s swings in blood sugar several times, Rondelli said.

On the first night, Slash woke up Rondelli when her son’s blood levels dropped below 80 three times, allowing her to give Mylon glucose.

Rondelli said that although her son has a monitor to test his levels, she said the device is designed for adults and can be inaccurate and slow. Slash offers a more immediate response, she said.

“He’s going to have a more real-time sense,” Rondelli said.

In the days they’ve been together, Rondelli said Slash has mostly been spot on — pawing at Rondelli when he detects Mylon needs his blood sugar tested. But the dog is still new to training.

At the firehouse Wednesday, Slash pawed at Rondelli. She took her son to a chair and checked his blood levels with Slash at his feet. But the results showed Mylon’s levels were normal.

It turns out Slash had detected off-kilter blood sugar for a firefighter who also is diabetic.

In that case, Slash didn’t get a treat — a way of training him to alert the family only if it is Mylon experiencing problems.

It’s unclear what chemical dogs are detecting when they sense someone’s blood sugar has gone too high or low. And research appears to be mixed when it comes to the effectiveness of diabetic-alert dogs.

But Rondelli is convinced Slash is going to be a great help to her family.

“There’s amazing technology out there,” she said, “but dogs just have an amazing sense.”