Prep the produce: Scrub the carrots well and trim the ends. Peel the oranges and remove as much white pith as possible.
Peel the lemon and ginger if using. Cut everything into chunks that fit your juicer or blender.
If using a juicer: Juice the carrots first, then the oranges, lemon, and ginger. Stir the juice to combine.
Taste and add a pinch of salt if you want the flavors to pop.
If using a blender: Add carrots, oranges, lemon, and ginger to the blender with 1/2 cup cold water. Blend on high until smooth, adding more water as needed to keep things moving.
Strain (blender method): Pour the mixture through a fine-mesh sieve or nut milk bag into a bowl or pitcher. Press or squeeze to extract as much juice as possible.
Finish and adjust: Stir in the optional oil for better absorption of fat-soluble nutrients.
Taste and adjust acidity with extra lemon or sweetness by adding another orange if needed.
Serve: Pour over ice if you like it extra cold. Enjoy immediately for the freshest flavor and maximum nutrients.