Preheat the oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or grease the cups.
In a large bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt.
In a separate medium bowl, whisk the melted unsalted butter, egg, whole milk, and vanilla extract until combined.
Pour the wet ingredients into the dry ingredients and gently fold together using a spatula until just combined. Do not overmix; the batter should be slightly lumpy.
Carefully fold in the fresh blueberries, ensuring they are evenly distributed without crushing them.
Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full.
Bake in the preheated oven for 18 to 20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove the muffins from the oven and allow them to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.