Patients should fast for at least 12 hours before they have a fasting blood test, according to St. John Providence Health System. Not all blood tests require patients to fast, but those that do require that patients abst... More »

A person needs to fast for 8 to 12 hours before a blood test. Fasting is necessary so that accurate results can be reported. More »

www.reference.com Health Diagnostics & Imaging

Fasting for a certain length of time before a blood test is one way of ensuring that your test results are not contaminated by the food you've eaten. The Mayo Clinic notes that fasting may not be necessary to get an accu... More »

According to Quest Diagnostics, a lipid or glucose tolerance test requires eight hours of fasting. Health care providers may have other recommendations, depending on the type of test. More »

A person needs to fast for 8 to 12 hours before a blood test. Fasting is necessary so that accurate results can be reported. More »

www.reference.com Health Diagnostics & Imaging

Patients are required to fast for 8 to 16 hours before a glucose tolerance test in order to eliminate the effects of recent meals on blood sugar levels, according to WebMD. This provides an accurate reading of the patien... More »

Preparing for a PET (positron emission tomography) scan generally involves fasting for several hours before the test, as well as avoiding intense levels of exercise for a couple of days beforehand. The doctor may also pr... More »

www.reference.com Health Diagnostics & Imaging