Abstinence from food. Occurs overnight it most people.
Patients may be labelled NBM (short for "nil by mouth"). Take care what you mean here. For example, it may be unacceptable to have a large meal in the few hours before a general anaesthetic but quite acceptable and safer to allow normal oral medications with a little water for a patient on oral therapy for say Parkinson's disease or epilepsy. Indeed, in patients with normal gastric emptying, carbohydrate drinks are given 2 hours before surgery as a component of enhanced recovery after surgery.
There are likely to be relevant clinical guidelines if you are not sure.
- Fasting before surgery/GA
- Fasting glucose/lipids