Guide

Most STD blood tests do not require fasting, but a few combined panels or added labs may need 8–12 hours with only plain water.

Most hepatitis blood tests do not require fasting, but follow your lab’s instructions in case other fasting blood work is ordered with them.

No, most thyroid blood tests do not require fasting, but follow your lab’s prep instructions if they ask you to avoid food or supplements.

No, you usually do not need to fast before a TSH blood test, unless your doctor orders other labs that must be done on an empty stomach.

Most routine urine checks don’t need fasting, but a few specialized tests or combined panels may include short food and drink limits.

No, you usually don’t need to fast before providing a urine sample for drug screening, unless your clinic gives different directions.

No, most A1C tests do not require fasting, unless your clinician orders other fasting blood work at the same visit.

Yes, most liver ultrasound appointments ask you to fast for about 6 to 8 hours so your upper abdomen shows clearly on the scan.

Most labs do not need fasting for a potassium test, but follow any instructions if other fasting blood work is ordered at the same time.

Yes, standard thyroid blood tests rarely need fasting, unless your clinician asks for fasting because other labs are done at the same time.