In a medium saucepan, combine the fresh blueberries, granulated sugar, and water. Stir gently to mix the ingredients without crushing the blueberries.

Place the saucepan over medium heat. This allows the sugar to dissolve and the blueberries to release their juices, creating a flavorful base for the syrup.

Bring the mixture to a gentle boil, then reduce the heat to low. Allow it to simmer for about 10 minutes, stirring occasionally. This simmering process helps to break down the blueberries and intensifies the flavor.

After 10 minutes, remove the saucepan from heat. Using a fine mesh strainer, strain the mixture into a bowl or another saucepan. This step separates the syrup from the blueberry skins and seeds, resulting in a smooth texture.

Press down on the blueberries with the back of a spoon to extract as much liquid as possible. Discard the solids.

Return the strained syrup to the saucepan. Stir in the fresh lemon juice and vanilla extract (if using). This adds a refreshing acidity and depth of flavor to the syrup.

Simmer the syrup on low heat for an additional 2-3 minutes to thicken slightly. The syrup should coat the back of a spoon when ready.

Remove from heat and let it cool slightly before transferring to a storage jar or bottle.