He was driving to his home in Skippack, Montgomery County, that same day when he decided to pursue the most demanding of sports.
"I have two young sons," Holder said of Nico, now 8, and Luka, now 6. "I didn't want them to grow up and see me limited in any way. I didn't want them to think they could be limited in any way. I didn't want kids who have diabetes to think they could be limited in any way.
"I was driving home from the doctor's office that day and I'm telling my wife [Jude] on the phone, 'I'm doing this.' "
Within six months, Holder was competing in half-ironman competitions, shorter versions of the sport's three-event format - swimming, bike riding, and distance running.
By the spring of 2006, Holder was finishing his first full ironman event, which features a 2.4-mile swim, 112-mile bike ride, and 26-mile run.
"Andy is amazing," said Holder's trainer, Bill Hauser of Mid-Atlantic Multi Sport, a Philadelphia-based coaching service that specializes in endurance sports. "He was determined. He made it happen through his hard work and determination."
The Philadelphia Insurance Triathlon uses Olympic distance - 1.5-kilometer swim, 40-kilometer bike ride, and 10-kilometer run.
This will be Holder's first time competing in the seven-year-old Philadelphia event. In the last three years, he has participated in an ironman event in Coeur d'Alene, Idaho, on the same weekend.
"It's going to be great to compete in Philly with family and friends around," Holder said.
Holder, who grew up in New York and graduated from Syracuse University, was a wrestler and football player as a youth. After college, he stayed in shape by lifting weights, occasionally competing in bodybuilding events.