Considering can be used in the following ways:
as a preposition (followed by a noun): Considering her lack of experience, it is surprising she has achieved so much.
before words such as that, what, or how to form a conjunction. The word ‘that’ is sometimes left out: Considering (that) he’s 82, he does very well. ♦ He does very well, considering how old he is.
in spoken English, as a sentence adverb at the end of a sentence (making a comment on the whole sentence or clause): He does very well, considering.