Diabetes screening and management: glucose tests

A blood glucose test will screen for diabetes, and assess the effectiveness of current treatments. Diabetes can lead to serious complications, so regular screening is important.

Glucose tests measure the amount of sugar in your blood and are used to screen for diabetes or assess the effectiveness of diabetes treatments. Persistently high glucose levels are a hallmark of diabetes and require prompt management to prevent serious complications.

• The fasting blood glucose test: This test is simple, and you don't eat for eight to 12 hours before a blood sample is taken. Glucose levels above seven millimoles per litre (mmol/l) of blood on two ­occasions indicate diabetes. (Levels below six are considered normal, and levels of six to seven indicate potential problems that may lead to diabetes.)
• Postprandial blood glucose test: This blood glucose test is taken two hours after eating, and it may be more accurate. A level of 11 or above indicates diabetes.
• Oral ­glucose tolerance test: If these tests are inconclusive, an oral ­glucose tolerance test may be done. You are given a high-glucose beverage to drink, then glucose levels in the blood and urine are measured for several hours afterwards.
• Hemoglobin A1c test: If you already have diabetes, a hemoglobin A1c test (also called a glycated hemoglobin test) is used to assess whether your therapy is effective. It provides a good estimate of average blood glucose values over the previous eight to 10 weeks. Home monitoring is also important.

The Canadian Diabetes Association recommends blood glucose testing be performed every three years in people age 45 or older. You'll need this test more often if the following applies.

• You're obese and/or physically inactive.
• You have high blood pressure.
• You have high cholesterol.
• You are aboriginal, black or Hispanic.
• All of the above. Glucose testing may be need­­ed earlier than age 45 and be done more often than every three years. Discuss frequency with your doctor.

• If you have Type 1 diabetes, you may need to monitor your glucose levels at home four or more times a day to assure that blood sugar levels are under tight control.
• Many people with Type 2 diabetes check their glucose level just once a day. However, testing more frequently than this allows for better control of your blood sugar levels and the disease.
• Regardless of what type of diabetes you have, aim for pre-meal glucose levels between 4.0 and 7.0 mmol/l, and bedtime levels between 5.5 and 7.7.

• Several types of home test kits are available. The most popular one uses a special lancing device to draw a drop of blood from your fingertip. The blood is placed on a test strip and read by a meter that gives you your glucose levels in less than a minute. Other devices draw minute amounts of blood from your forearm, which is often less painful than pricking your finger.
• In addition to measuring glucose, some home monitors measure substances in the blood called ketones, which can build up in the body and cause a life-threatening complication called diabetic ketoacidosis. A home test kit for hemoglobin A1c is also now available.
• Gluco­Watch Biographer: A new type of monitor, the Gluco­Watch Biographer, is a battery-powered device you wear on your wrist like a watch. It measures glucose levels by sending painless electrical currents through the skin. After a three-hour warm-up and an initial calibration with a traditional finger stick, the watch can provide a glucose reading every 20 minutes for up to 12 hours, even during sleep (an alarm is triggered if there’s a problem). This device should be used only in combination with finger-stick testing.