User blog comment:KiruSama/Levi and the Titan Serum/@comment-174.116.149.229-20151125222926

I don't really like the idea of Levi becoming a Titan Shifter. Honestly, I like him the way he is, strong and totally op ♡

Also, if he used the serum on another Titan Shifter it wouldn't have and effect. The point of the serum is to have the human transform into a Titan, so if that was already done, the effect would either be nulled or stop the Titan Shifting abilities altogether (in my opinion).