Currently there's no penalty to the player in using the vacutainer on the player survivor, or any corpse for that matter. Doesn't seem like a big thing; blood has a nutrition and quench of 5, and an enjoyability of -50, plus it negatively affects player health.
However, a survivor with optimist, spiritual, gourmand, and cannibal can bypass the negative effects of consuming blood, getting a morale buff in the process. If player has the leukocyte breeder CBM, their survivor can pretty much survive on nothing but their own blood, and getting a morale buff from doing so.
I reckon that limiting the number of times the vacutainer can be used in a 24-hour period, or using it causes pain or damage might help avoid the exploit.
Drawing blood from yourself should increase your hunger and thirst by more than drinking it provides, since the body needs to rebuild the blood.
True, though a limit still has to be set, as you can draw blood from corpses, and as long as the corpse doesn't give tainted meat, all blood is considered human blood for some reason. Carp, triffids, giant slug, wolf, spiders - all human blood. Zombies and mi-gos too, though their blood is also poisonous.
Most helpful comment
Drawing blood from yourself should increase your hunger and thirst by more than drinking it provides, since the body needs to rebuild the blood.