Before a fasting blood test, a patient may only consume water and must abstain from any other foods or liquids, according to Quest Diagnostics. Fasting is necessary before certain blood tests in order to obtain accurate ... More »

It is okay to drink water before having a blood test. According to NHS Choices, even when blood tests require fasting, the person being tested is still normally allowed to drink water. More » Health Medical Ranges & Levels

As a general rule, patients should avoid eating or drinking anything other than water during the 12 hours prior to any blood test. Blood tests specifically prohibiting alcohol consumption in the 24 hours prior to the adm... More »

Unless specifically requested by a doctor, fasting is typically not required prior to a prostate-specific antigen, or PSA, blood test, according to Lab Tests Online. If fasting is required, patients must consume no food ... 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 »

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 patient fasting for blood tests may have water during his fast, according to Quest Diagnostics. It is advisable to drink a lot of water during the fast because it is harder for care providers to draw a patient's blood ... More »