Due to the shortage of willing vampire donors, human drainers attack vampires and drain their entire blood supply, either staking the vamps or leaving victims to die in the sun.
The constant threat of a high blood sugar level can cause hyperactivity and conversely, low blood sugar level will cause lethargy and eventually unconciousness.
With arterial thrombosis, blood vessel wall damage is required, as it initiates coagulation, but clotting in the veins mostly occurs without any such damage.