What does it mean if my one eyelid starts to droop?

Eyelid droop: It could mean anything from a stroke to bell's palsy to eyelid swelling from infection - this needs immediate attention.

Ptosis: A droopy lid can be secondary to a number of causes. The most common cause is age. Depending on if you have any other eye findings with it will help to determine the cause. You should definitely see your eye dr for further evaluation.

See an eye doctor: New lid droop always needs to be evaluated. Although most of the time it is benign, there may be conditions that have to be addressed. Often, medical or surgical treatment can help, so don't delay seeing an eye doctor.

Droopy eyelid: There are several causes of a droopy eyelid. Your best bet would be to have your eyes evaluated by a board certified facial plastic surgeon.