I believe that Rick Deckard is an android. At the alternate police station, while he and Garland are waiting for the other bounty hunter, Resch, to get back with testing equipment, Garland tells Rick that Resch is an android. Resch returns and kills Garland, and the following exchange takes place:
"What did it say to you while I was gone?"
"That he--it--was an android. And you--" Rick broke off, the conduits of his brain humming, calculating, and selecting; he altered what he had started to say. "--would detect it," he finished. "In a few more minutes."
Later, when Rick tests Resch, the reader is not told the result. Rick continues to believe that he himself is human; however, neurons don't hum. They have pathways, not conduits. Moreover, the novel never establishes any difference between androids and human beings. What it does do is confirm the truth of Buddhism, which is that the ego, the "I" does not have an independent objective existence, but is dependent upon something which is its own cause.
"Do Androids Dream" is like the Anatma Lakshana Sutra turned into a paperback detective novel. The title of the sutra means "Discourse on the Characteristics of That Which is Not Self." Thus we learn that form, feelings, relative knowledge, subconsciously willing things to happen, and the resultant awareness of thoughts, are not what makes up Self, or God, although none of these things would exist without Self. Dick even gives androids intuition, an attribute of Self. Therefore, Philip Dick appears to be attempting (crudely) to say that humans believe themselves to possess attributes that the entities they build can never possess--some of which are ego and some of which are Self. However, the five attributes of ego are impermanent and changing, and therefore do not exist in humans or their creations, while the attributes of Self are permanent and immutable in both humans and their creations. And this is because that which creates a human being also creates whatever the human imagines it creates.
"Mahamati, it is like Pisaca, who by means of his magic makes a corpse or a machine-man dance with life though it has no power of its own: the ignorant cling to the non-existent, imagining it to have the power of movement." The Lankavatara Sutra