Do I need to fast before every blood test?

No. Some tests require fasting and others do not. Follow the instructions for the tests actually ordered rather than assuming every blood draw needs the same preparation. MedlinePlus fasting guidance.

Ask about food, drinks and your usual medicines before the appointment. Do not stop a prescription simply because you have been told not to eat.

If you ate or drank something outside the instructions, tell the person drawing your blood. That lets the team decide whether the sample can still answer the intended question.

Next: Confirm preparation instructions when your lab visit is arranged.