There are many successful diabetic athletes. Do a Google search on "type 1 diabetic athletes" and you'll see that diabetes will add some extra challenges but doesn't mean that your athletic performance must suffer.
Here is a partial list of diabetic athletes. There's also a pro cycling group called "team type 1"
Wasim Akram - Pakistani cricket fast bowler
Arthur Ashe - Tennis - Wimbledon winner
Walter Barnes - Football and actor. Before acting career he played professional football for the NFL's Philadelphia Eagles, 1948-1951.
Sarah Bina - Championship clogger
Ayden Byle - Runner - First insulin-dependent man to run 6521.5 km across North America.
Nick Boynton - Hockey Player - Boston Bruins
Doug Burns – Fitness consultant, Record-holding strength athlete
Sean Busby - Champion Snowboarder
Bobby Clarke - NHL - Philadelphia Flyers
Ty Cobb - MLB - Detroit Tigers
Scott Coleman - Swimmer - first man with diabetes to swim the English Channel, (August 17th 1996)
Jay Cutler - Football Player
Chris Dudley - NBA - New York Knicks center
James “Buster” Douglas - Heavy Weight Boxer
Kenny Duckett - NFL - New Orleans Saints
Rick Dudley - Hockey
Scott Dunton - World Class Surfer
Mike Echols - NFL - Tennessee Titans
Pam Fernandes - Para Olympian
Missy Foy - Professional Marathon Runner
Curt Frasier - NHL - Chicago Black Hawks
Walt Frazier - NBA - New York Knicks
“Smokin’ Joe” Frazier - Boxing
Kris Freeman - Olympic and National Champion Cross-Country Skier
Joe Gibbs - NFL - Washington Redskins coach
Bill Gullickson - MLB - Cincinnati Reds Pitcher
Gary Hall Jr. - US Olympic Gold Medalist, Swimming
Jonathan Hayes - NFL - Pittsburgh Steelers, Kansas City Chiefs
Dave Hollins - 1993 Phillies World Series Third Baseman
James "Catfish" Hunter - MLB - Pitcher, Baseball Hall-of-Famer
Chuck Heidenrich - Skiing
Chris Jarvis - World Champion Canadian Rower
Jason Johnson - MLB - Pitcher, Cleveland Indians
Kelli Keuhne - LPGA golfer
Billie Jean King - Tennis
Jay Leeuwenburg - NFL - Indianapolis Colts Lineman
Mark Lowe - Major League Baseball
Michael Earl Malone - Son of former NBA star Moses Malone.
Robert "Gorilla Monsoon" Marella -Professional wrestler and commentator
Michelle McGann - LPGA golfer
Adam Morrison - Basketball Player, Gonzaga University
Brandon Morrow -Seattle Mariners Pitcher
David Pember - MLB - Milwaukee Brewers
Toby Petersen - NHL - Pittsburgh Penguins, Dallas Stars
Sir Steven Redgrave - Rower - Winner of five consecutive Olympic gold medals
Dan Reichert - MLB - Kansas City Royals
Ham Richardson – Tennis star
Jackie Robinson - Baseball Player
Sugar Ray Robinson - Boxing
Ron Santo - MLB - Chicago Cubs legend
Mike Sinclair - NFL - Philadelphia Eagles
Kendall Simmons - NFL - Pittsburgh Steelers
Hank Stram - NFL - Kansas City Chiefs Coach
Bradley Suttle - Texas Longhorns - Second Baseman
Bill Talbert - Hall of Fame tennis player
Sherri Turner - LPGA golfer
Scott Verplank - PGA golfer
Everson Walls - Football player
Jo Ann Washam - LPGA golfer
David "Boomer" Wells - San Diego Padres Pitcher
Wade Wilson - NFL player and Dallas Cowboys quarterback coach