At a glance
Also known as
Blood sugar; blood glucose; BSL; oral glucose tolerance test; OGTT; GTT
Why get tested?
To determine whether or not your blood glucose level is within the reference range; to screen for, diagnose, and monitor diabetes, and monitor blood glucose levels where required
When to get tested?
If you have symptoms suggesting (high blood glucose) or (low blood glucose), if you are pregnant, or if you are diabetic, testing can take place up to several times a day to monitor glucose levels
A blood sample drawn from a vein in your arm, or for a self check, a drop of blood from your finger will be sufficient
What is being tested?
Glucose is a sugar that serves as the main source of energy for the body. The carbohydrates we eat are broken down into glucose (and a few other sugars), absorbed by the small intestine and circulated throughout the body. Most of the body's cells require glucose for energy production; the brain and nervous system cells rely on glucose for energy, and can only function when glucose levels in the blood remain within a certain range.
The body's use of glucose depends on the availability of insulin, a hormone produced by the pancreas. Insulin acts to control the transport of glucose into the body's cells to be used for energy. It also directs the liver to store excess glucose as glycogen (for short term energy storage) and promotes the synthesis of fats, which form the basis of a longer term store of energy. Balanced levels of glucose and insulin are essential for life.
Normally blood glucose levels rise slightly after a meal, and insulin is released to lower them, with the amount of insulin released matching the size and content of the meal. If blood glucose levels drop too low, such as might occur in between meals or after a strenuous workout, glucagon (another hormone from the pancreas) is produced to release liver glucose stores, raising the blood glucose levels. If the glucose/insulin system is working properly the amount of glucose in the blood remains fairly stable.
and , caused by a variety of conditions, can be life threatening, if severe and sudden changes occur, causing organ failure, brain damage, coma, and, in extreme cases, death.
Long-term high blood glucose levels can cause progressive damage to body organs such as the kidneys, eyes, blood vessels, heart and nerves, such as occur in diabetes mellitus.
Untreated hyperglycaemia that arises during pregnancy (known as gestational diabetes) can cause mothers to give birth to large babies, who may have low glucose levels. Long-term hypoglycaemia can lead to brain and nerve damage and ultimately coma and death.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm, or a drop of blood is taken from your finger by pricking it with a small pointed lancet.
Can I test myself at home for blood glucose levels?
If you are not diabetic there is usually no reason to test glucose levels at home.
If you have been diagnosed with diabetes, however, your doctor will recommend a home glucose monitor (glucose meter). You will be given guidelines for how high or low your blood sugar should be at different times of the day. By checking your glucose regularly, you can see if the diet and medication schedule you are following is working properly.
Can I test my urine glucose instead of my blood?
Not in most cases. Glucose will only show up in the urine if it is at sufficiently high levels in the blood so that the body is "dumping" the excess into the urine, or if the kidneys are damaged and the glucose is leaking out into the urine. Urine glucose, however, is sometimes used as a rough indicator of high glucose levels, and if it is detected further tests of blood glucose should then be carried out.
What are the usual treatments for diabetes?
For type 2 diabetes, which is the most common type of diabetes
, losing excess weight, eating a healthy low fat diet that is high in fibre, and getting regular amounts of exercise may be enough to lower your blood glucose levels. In many cases however, oral medications that increase the body's production of and sensitivity to insulin are necessary to achieve the desired glucose level. With type 1 diabetes (and with type 2 diabetes that does not respond well enough to oral medications), insulin injections several times a day are necessary.
How can a diabetes specialist nurse help me?
If you are diabetic, a diabetes specialist nurse (or sometimes a practice nurse) can make sure that you know how to:
- Plan meals (a dietician can help with this also). Diet is extremely important in minimising swings in blood glucose levels.
- Recognise and know how to treat both high and low blood sugar
- Test and record your self check glucose values
- Adjust your medications
- Administer insulin (which types in which combinations to meet your needs)
- Handle medications when you get ill
- Monitor your feet, skin, and eyes to catch problems early