expression
dim-witted; slow on the uptake
Idiomatic expression literally meaning 'blood circulation is bad', used to describe someone who is mentally slow or dull-witted. Often used in a critical or teasing manner.
彼は血の巡りが悪いから、説明してもなかなか理解できない。
He's slow on the uptake, so even if you explain it to him, he has trouble understanding.
そんな簡単なこともわからないなんて、血の巡りが悪いんじゃない？
If you can't even understand something that simple, aren't you a bit dim-witted?