B-total

Going "B-total" is - for a vampire - going totally without Blood. For some, they sign the Pledge and become a Black Ribboner, join either the Überwald League of Temperance or that of Ankh-Morpork. For others it is a personal choice, but forsaking all drinking of the B-vord leads to NOT being found with "an apple in their mouth and a clove of garlic where the sun does not shine wwwaiting for the stroke of the sharpened axe" (John Not-A-Vampire-At-All Smith, President of the Ankh-Morpork League of Temperance).

Annotation

The Roundworld reference is to going Teetotal, i.e. abstaining from all alcohol. The "T" stands for "Temperance".