Hi Lopper,
It depends what your blood test is for.
If its a "fasting blood test" then don't have anything except water for 12 hours before the test.
If its a cholesterol blood test then same as a fasting blood test.
If its an HBA1C test then you don't need to fast at all.
If you're not sure what the test is for, then play it safe and don't eat or drink anything except water for 12 hours beforehand.