Born in Klaipėda, Lupeikis was never selected to race in the Tour de France, but he did compete at the Vuelta a España in 1992 and 1997 as well as the Giro d'Italia in 1992. He won the Tour de Berlin in 1994. In 1995 he won a silver medal in the Men's points race at the 1995 UCI Track Cycling World Championships in Colombia. He won Lithuanian Sportsman of the Year that same year. He won the Tour d'Egypte in 2000. Also in 2000, he was Lithuanian champion in the individual time trial. He retired from cycling in 2002, after becoming Lithuanian champion in the road race.