Blood Glucose

1 - Introduction 

2- Several different types of blood glucose tests are used

 

Introduction 

A blood glucose test measures the amount of a type of sugar, called glucose, in your blood. Glucose comes from carbohydrate foods. It is the main source of energy used by the body. Insulin is a hormone that helps your body use and control the amount of glucose in your blood. Insulin is produced in the pancreas and released into the blood when the amount of glucose in the blood rises.

Normally, your blood glucose levels increase slightly after you eat. This increase causes your pancreas to release insulin so that your blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels.

  

Several different types of blood glucose tests are used.

•  Fasting blood  sugar (FBS)

 

The "gold standard" for diagnosing diabetes is an elevated  blood sugar level after an overnight fast  at least 8 hours (not eating anything after midnight).It often is the first test done to check for diabetes.  A value above 140 mg/dl on at least two occasions typically means a person has diabetes. Normal people have fasting sugar levels that generally run between 70-110 mg/dl.

 

• 2-hour postprandial  blood sugar (2-hour PC)

 

 Measures blood glucose exactly 2 hours after you eat a meal.

 

• Random  blood sugar (RBS )

 

Measures blood glucose regardless of when you last ate. Several random measurements may be taken throughout the day. Random testing is useful because glucose levels in healthy people do not vary widely throughout the day. Blood   glucose levels that vary widely may indicate a problem. This test is also called a casual blood glucose test. 

 

• Oral glucose  tolerance test (OGTT)

 

An oral glucose tolerance test is one that can be performed in a lab. The person being tested starts the test in a fasting state (having no food or drink except water for at least 8 hours but not greater than 16 hours). An initial blood sugar is drawn and then the person is given 75 grams of glucose, (or 100 grams for pregnant women). The person then has their blood tested again 30 minutes, 1 hour, 2 hours and 3 hours after drinking the high glucose drink.

 

For the test to give reliable results, you must be in good health (not have any other illnesses, not even a cold). Also, you should be normally active (for example, not lying down or confined to a bed like a patient in a hospital) and taking no medicines that could affect your blood glucose. The morning of the test, you should not smoke or drink coffee. During the test, you need to lie or sit quietly.

The oral glucose tolerance test is conducted by measuring blood glucose levels five times over a period of 3 hours.  In a person without diabetes, the  glucose levels in the  blood rise following drinking the glucose  drink, but then fall quickly back to normal (because insulin is produced in response to the glucose , and the insulin has a normal effect of lowing blood glucose .)  In a diabetic, glucose  levels rise higher than normal after drinking the glucose  drink and come down to normal levels much slower (insulin is either not produced, or it is produced but the cells of the body do not respond to it) .