I actually saw a science video thing about this. Cutting off ones own limb in desperate starvation would more often than not result in death. If you did manage to survive unless the wound could be cauterized as it was being removed then the blood loss would weaken you more than the starvation to the point where you are cannot move or it would outright kill you. The amount of veins and arteries severed would pump out blood much too quickly for any starving person to live off their own limbs. You’d get maybe minute of in game time to bandage or cauterize else face death. Removal in a professional environment can still sometimes result in death. The only reasonable times that you would want to remove a limb is if A. Zombie Bites meant you would die in a matter of days. B. You were caught in a trap that meant freeing yourself would require the loss of a limb. C. You had extreme frostbite. D. You had nothing left to live for.
While it would be a nice feature if absolutely necessary, you’d need to do it in a the presence of a medical professional or have some way to replenishing your blood afterwards