Click in the Eyewitness News story window above to watch Jovana Lara's report, including an interview with the doctor.
But Dr. Pietro Galassetti may have found a painless way to collect those numbers.
Galassetti collected breath samples from diabetic children while blood sugar levels were high and as levels fell in response to insulin.
Using a technique developed to test air pollution, chemists detected high concentrations of methyl nitrate, a byproduct of the damage to body tissue, when blood sugar levels are too high.
"And we saw that the children who had high blood sugar had very high methyl nitrate in their breath, and then as we gradually corrected the blood sugar, the methyl nitrate in their breath was coming down," Galassetti said.
While still five-to-10 years off, Galasetti said he sees a hand-held breath analyzer replacing the blood test.
"Not having to stop and test his blood -- just be able to blow into a canister or whatever. It'll be pretty amazing," said Robby's mother Julie Mansfield.
"It would be a lot easier. I could have more of a normal life without having to step out every couple of hours to test my blood sugar," Robby said.
If it's easy, kids are more likely to do it. Controlling glucose levels now lowers Robby's chance of complications down the road and increases his shot at the big leagues.
Breath analysis has already shown promise in diagnosing ulcers and cystic fibrosis, and Galassetti said we may eventually be able to monitor insulin and cholesterol with a breath test.