Guide

Most vitamin B12 blood tests do not strictly require fasting, but many labs prefer 6–8 hours without food to keep results consistent.

You will usually be asked to fast 8–12 hours before a basic metabolic panel, but follow the timing your doctor or lab gives you.

Yes, most basic metabolic panel blood tests ask you to fast for 8–12 hours, unless your doctor or lab gives different directions.

Yes, most basic metabolic panel blood tests are done after 8–12 hours without food so glucose and other values reflect a steady baseline.

No, you usually do not need to fast before an MRI, unless your doctor or imaging center gives you specific fasting instructions.

No, an A1C blood test usually does not require fasting because it reflects average blood sugar over the past two to three months.

No, most routine workplace and urine drug checks do not require fasting, but always follow any instructions from your testing site.

You usually do not need to fast for a routine drug test, but always follow the specific directions from your lab or employer.

No, most drug screens do not require fasting, but follow your lab’s instructions about food, drink, and medications before testing.

Fasting for a CT scan depends on the body area and contrast dye, so follow the specific instructions from your imaging team.