A person needs to fast for 8 to 12 hours before a blood test. Fasting is necessary so that accurate results can be reported.
Before the test, a person should not eat food or drinks. He or she is only permitted to drink water to stay hydrated, which makes it easy to draw blood from the veins. However, there are claims that fasting does not make much difference in the results of the test, but most doctors advise their patients to fast. It is necessary to speak to a doctor, before the fasting period, especially for those who are on medication.