What causes my lower lip to protrude past my upper lip? (Photo)

Thank you for your question. There are options to make your lips look more youthful because injectables can create fuller, younger, sensual looking lips and help to improve your self confidence. I suggest that you consult with a board certified facial plastic surgeon.
Best wishes,

Most people's bottom lip is bigger than their top, however, this can also be due to teeth and jaw alignment. These fillers, (Volbella, Restylane, Juvederm) are good to create full and symmetrical lips. Nova threads can be used to improve lift and shape. Implants or fat are alternatives. I recommend getting a formal evaluation with a facial sculpting expert. Best, Dr. Emer

The lower lip usually is a bit bigger than the upper lip. Your dentition could also be contributing to your lip protruding more. I suggest you see a specialist and you can consider fillers as well to balance you out.