What's new in diabetes care
Introduction to diabetes
Types of diabetes
Diagnosis
Risk factors & screening

Glucose monitoring

• Is urine glucose testing useful?
• Blood glucose monitoring
• HbA1c (A1c) - glycated haemoglobin
• Blood glucose tests
• Recommended targets for diabetes control

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Is urine glucose testing useful?

This test is only suitable in stable type 2 diabetics when patients unable or unwilling to perform blood glucose tests. It should be supplemented by regular blood tests.

Best time for urine testing is morning before breakfast or 2 – 3 hours after a meal. It can be done 1 – 2 times per week. The test should be performed on a double voided specimen e.g. empty your bladder first, then test a sample passed 30 minutes later.

There are disadvantages of urine testing. It is less accurate than the blood glucose testing. It only becomes positive when blood glucose >10 mmol/l. It does not give an indication of blood glucose at time of test and cannot tell if blood glucose is too low. This is because it dependent on renal threshold for glucose.

Glucose in the urine (glycosuria) may occur in the absence of diabetes; conversely, diabetes may be present without glycosuria. Lowered renal threshold for reabsorption of glucose also cause glycosuria. The renal threshold for glucose varies between individuals. Thus, patients with a low renal threshold will tend to show glycosuria more readily than patients with a high threshold. Children have lower renal threshold and elderly patients tend to have higher renal threshold. Fluid intake, urine concentration and certain drugs may influence tests for glycosuria.

Blood glucose monitoring

Traditionally, fasting blood glucose and HbA1c measurements are recommended to monitor blood glucose control. Recent evidence however suggests that control of post-prandial hyperglycaemia is of importance to achieve excellent overall glycaemic control as reflected by HbA1c levels.

HbA1c (A1c) - glycated haemoglobin

It reflects mean plasma glucose concentrations over a period of 2 months. It therefore provides a better overall assessment on mean blood glucose control. However, the A1c measurement does not indicate sudden changes nor give any indication of day to day variation. Furthermore, the test can be affected by various medical conditions. For example, it can be abnormally low in haemolysis (breaking down of red blood cells), any condition that causes increased red cell turnover, blood loss, or abnormal haemoglobin such as HbS, HbC. On the other hand, it can be abnormally high in thalassaemia, and kidney failure (due to carbamylated Hb). HbA1c levels < 6.5% reflects satisfactory blood glucose control.

Blood glucose tests

Blood glucose tests can be performed after an overnight fast, before meal or 2 hours after the start of a meal.

Fasting blood glucose tells whether the insulin you make or take is controlling blood glucose overnight.

Pre-meal glucose can help guide decisions about food and insulin for the coming meal.

After-meal glucose tells whether your body had the right amount of insulin to cover the food you ate. This is the test that helps you learn the most about your food choices.

Recommended targets for diabetes control

Recommended target for diabetes control (from American Diabetes Association and International Federation of Diabetes) are as follow: