Bring 4 cups of water to a boil. Remove from heat and steep the tea bags for 5–7 minutes. Remove tea bags and let the tea cool slightly.
In a small saucepan, combine blueberries, sugar, and ½ cup water. Simmer over medium heat, mashing the berries with a spoon as they soften. Simmer 5–7 minutes until thickened slightly. Strain through a fine mesh sieve into a bowl or pitcher to remove solids.
Add the blueberry syrup to the brewed tea. Stir in lemon juice (if using). Refrigerate for at least 1 hour until chilled.
Pour over a glass filled with ice and garnish with lemon slices, blueberries, and mint if desired.
