Preheat the oven to 375°F and line a 12-cup muffin tin with paper liners or spray with non-stick cooking spray.
In a large bowl, whisk together all-purpose flour, vanilla or unflavored whey protein powder, baking powder, baking soda, and salt.
In a separate bowl, whisk together eggs, milk, maple syrup, vegetable oil (or melted coconut oil), and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and stir gently just until combined, leaving a few lumps.
Fold in fresh or frozen blueberries without thawing if frozen.
Divide batter evenly among the 12 muffin cups, filling each about two-thirds full.
Bake for 18–22 minutes, or until tops are golden brown and a toothpick inserted in the center comes out clean.
Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely or enjoy warm.