how long do you need to fast for a blood test

Most fasting blood tests need about 8–12 hours of no food and only plain water, but the exact time depends on which test you’re having and what your doctor orders. Some common tests, like fasting glucose and many cholesterol panels, often use an overnight fast of 8–12 hours so you can stop eating after dinner and test in the morning. Always follow the specific instructions on your lab form or from your provider, because some tests do not require fasting at all and others may have extra rules like avoiding alcohol for 24 hours.