18 The oral glucose - Nuffield Foundation（18口服葡萄糖-纳菲尔德基金会）.pdf

advanced applied science: GCE A2 UNITS © The Nuffield Foundation 2008 ACTIVITY BRIEF The oral glucose tolerance test The science at work Home blood glucose test kits are inexpensive and readily available. You may have seen them for sale at the pharmacy of your local supermarket or elsewhere. They are a valuable aid to diabetics who need to be able to control their blood glucose levels. Normally, nearly all glucose is reabsorbed by the kidneys during urine formation. Blood levels have to rise quite high before it starts to be lost in the urine. Urine glucose therefore gives only a rough indication of high blood glucose levels. Also, someone may show symptoms of, or be at a high risk of, contracting diabetes but have no detectable glucose in their urine. A blood test can reveal diabetes at lower glucose concentrations, even if there is none in the urine. Sadly, for unknown reasons, there has been an increase in type 1 diabetes in young people. Type 2 diabetes has been diagnosed in children in Europe and the USA for the first time, probably due to lifestyle changes involving diet and exercise. Since blood glucose levels will rise after a meal, the standard diagnostic test to confirm diabetes involves raising blood sugar levels after a fast and testing a blood sample two hours later. If the body’s control mechanisms are working correctly, this is long enough for blood glucose levels to fall back to normal. This test is the glucose tolerance test or GTT. As a sugary drink is taken, it is also known as the oral glucose tolerance test (OGTT). To think about One of the problems with diagnosing diabetes is the fact that there is quite a wide range for ‘normal’ blood glucose concentrations. Not only does blood glucose concentration vary due to uptake and use, but individuals also vary in what is normal for them. Another issue concerns the difference between the use of urine samples and blood samples for the diagnosis and management of diabetes.