Bring blueberries and lemon juice to a boil in a large saucepan over medium heat; cook, stirring occasionally, 5 minutes. Remove from heat; pour through a wire-mesh strainer into a bowl, using back of a spoon to squeeze out juice. Discard solids. Rinse saucepan clean.
Bring 4 cups water to a boil in same saucepan; add 3 tea bags; let stand 5 minutes. Discard tea bags. Stir in sugar and blueberry juice mixture. Pour into a pitcher; cover and chill 1 hour. Serve over ice. Garnish, if desired.