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.Continue Reading
NHS Choices explains that some blood tests do not require a person to refrain from eating or drinking normally. However, some tests require fasting from food or drink prior to the procedure. The only thing a person can consume, before a fasting blood test, is water. In some cases, the person may also be asked by the healthcare provider to avoid smoking before getting the test done.
The water deprivation test, as mentioned by Patient.co.uk, specifically instructs a person to avoid drinking water within a given amount of time. This test is used for the diagnosis of diabetes insipidus.Learn more about Medical Ranges & Levels