No. It's just a genjutsu, that distorts the victim's perception of time. Itachi can torture like he did to Kakashi and Part 1 Sasuke (2x), or he can use it and it have no negative effects on the victim; like against Hebi Sasuke and EMS Sasuke (during Kabuto fight).
Kakashi was surprised he was still alive an asked why Itachi didn't kill with Tsukuyomi which means Itachi was holding back.
Kisame was also surprised Kakashi was still alive after being hit by it which means that if Itachi wanted to he can make the torture of Tsukuyomi worse to the point it can kill you.
I think its more of a torture technique as a way to stun the enemy rather than kill them as it feels like you are being tortured for days rather than a minute. Though I guess if someone was caught in your genjutsu why not just walk up and stab them if they were your opponent instead of hoping they die of fear.