Bring 1 (16-oz.) package frozen blueberries and 1/2 cup fresh lemon juice to a boil in a large saucepan over medium heat. Cook, stirring occasionally, 5 minutes. Remove from heat, and pour through a fine wire-mesh strainer into a bowl, using back of a spoon to squeeze out juice. Discard solids. Wipe saucepan clean.
Bring 4 cups water to a boil in same saucepan; add 3 family-size tea bags, and let stand 5 minutes. Remove and discard tea bags. Stir in 3/4 cup sugar and blueberry juice mixture. Pour into a pitcher; cover and chill 1 hour. Serve over ice.