Double refers to the fact that not only do the test subject not know what treatment they are getting (e.g. real or placebo), but also the staff who administer that treatment do not know: both are blind, hence double. This is important because if the administrators know, then something in their behavior such as body language could leak the information to the test subjects.

If administrator and test subject are the same person, it cannot be double. However, you can take steps to prevent yourself from knowing what you're taking, like preparing identical containers which are randomized and whatnot. If there is no second human there serving to you who could leak clues then it may be as good as double blind.