Final answer:
The client should be fasting for 12-14 hours before an oral glucose tolerance test; during this time only, water is typically allowed. The test assesses the body's ability to tolerate glucose and is used for diagnosing diabetes mellitus.
Step-by-step explanation:
The client should be fasting (NPO) for 12-14 hours before an oral glucose tolerance test. During the fasting period, there are typically no restrictions on water intake, so the correct answer is (c) 6-8 hours, Water only. However, based on the reference information provided about the test, the fasting period should be 12-14 hours instead of 6-8 hours as stated in the options.
After the fasting period, the patient is given an oral dose of glucose, and their blood glucose levels are measured at intervals to assess their ability to tolerate glucose. This helps in diagnosing conditions such as diabetes mellitus. In a normal person, blood glucose levels rise after glucose administration and then fall back to normal, whereas in a person with diabetes, blood glucose levels rise significantly and do not return to normal within the expected time frame.