Geoffrey Cox used to be happy to show curious friends his glucose test meter, how he pricks his finger to test his blood sugar level and the insulin pump that's attached to his stomach through a tube.

But over the years, he'd hear the same kind of questions about his weight and eating habits and now — at the age of 13 — has learned to keep the details of his type 1 diabetes to himself.

"It just gets tiring to explain it," Geoffrey said with a sigh. "They don't understand the concept of where type 1 diabetes comes from."

But to try and clarify misconceptions, Geoffrey forged ahead.

"It's not caused by eating too much sugar," he said. "It's your white blood cells killing your beta cells in your pancreas, which produces the insulin. It's not very common and it's not spreadable. I would just like to educate people because it gets frustrating."

Geoffrey began the eighth grade at Kaimuki Middle School this fall and thinks he'd like to have a career either working with horses or building or designing cars or buildings.

He's an active kid who has played soccer, paddled and is currently training for the Ho-nolulu Marathon. But each athletic activity turns into an exercise in math and physiology as Geoffrey and his mother try to calculate how his glucose levels will rise and fall — and how much insulin and food he'll need in advance.

Participating in each individual sport also depends on whether Geoffrey needs to detach himself from his insulin pump.

"It gets annoying to take everything off just to go swimming," he said.

His mother, Lori McCarney, president of the Hawai'i chapter of the Juvenile Diabetes Research Foundation, worries that his diabetes is preventing Geoffrey from joining activities he might love.

"It's one of the things that's kept him out of a lot of sports," she said. "He's generally shy and the idea of being different is weighing on him more than I hoped it would."

She also knows that her son faces lots of temptations from unhealthy food. And it can be scary trying to let him make his own choices as a teenager.

"Kids at a certain age feel that they're indestructible and are going to live forever, nothing they do is going to threaten their life," McCarney said. "In Geoff's case, he doesn't internalize the long-term effects of some of the choices he makes. If he lets himself get really high blood sugars, he could go blind, he could damage his kidneys, he could lose limbs. I don't want to scare him. But trying to figure out how you communicate the risks to a teenager is pretty hard."

MAKING ADJUSTMENTS

Geoffrey was just 20 months old when McCarney noticed that he was constantly thirsty and his diapers were soaked.

"I didn't know what was going on," she said. "One day he was just sick, throwing up."

In the emergency room, doctors told McCarney that he could have slipped into a coma and died.

"I've been living with that experience for more than 11 years," McCarney said, reliving the moment she learned her son had type 1 diabetes.

McCarney has 19-year-old twins but raising two boys did nothing to prepare her for a third child with diabetes.

She had to deal with their jealousy over the attention Geoffrey got while worrying about managing his disease.

He was still a toddler one day when Geoffrey had what appeared to be a typical inconsolable, childhood temper tantrum.

"I finally decided to check his blood sugar and he was real low," McCarney said. "You feel like a real bad mom."

McCarney, who is a senior vice president at Coldwell Banker Pacific Properties, also had to find daycare providers willing to prick his skin every three to four hours to check his blood sugar.

"They wondered what would happen if he went into a diabetic shock," she said. "People were afraid to take that on. My concern was my son could die. So it's hard on the parents and it's hard on the daycare providers."

At the start of each school year at Kahala Elementary School, McCarney would talk to Geoffrey's teachers about what he had to do every day and what the teachers should look for. Luckily, McCarney said, Geoffrey had the same school health aid at Kahala every year, who checked his glucose levels before lunch when he was younger.

Each week or so, McCarney would go over the school lunch menus and make a spread sheet that roughly calculated each meal's calorie and carbohydrate counts. Then she would try to predict how much insulin she should inject into him before school, based on what he would eat later in the day.

"It's just a lot of math and a lot of management," she said. "But then, can you make the kid eat what they're supposed to eat? Or are they going to eat what they want to eat?"

'SCARY SOMETIMES'

Before he got his insulin pump six years ago, Geoffrey never had to be injected with insulin at school. And McCarney always worried what would happen if he needed a shot.

"School health aids can't prick his skin (for glucose tests) or give injections," she said. "How does that get managed for diabetic children?"

And by the time he entered the fourth grade, Geoffrey started to shy away from of all of the questions from his classmates. "Does it hurt when you prick your finger? ... Why do you have that tube coming out of you?"

With the insulin pump, an alarm or buzzer goes off when Geoffrey's blood glucose level drops too low, telling him that he needs to manually give himself a bit more insulin.

But McCarney worries that he'll choose his desire to fit in with classmates over his health.

"Sometimes he needs to give himself a bolus of insulin from his pump, which means unclipping the pump, pulling it out and giving himself more insulin," she said. "But he doesn't do it sometimes because he doesn't want to pull it out in front of other kids.

"It gets scary sometimes letting him find his own way."