When it comes to diabetes, some of the most important lab tests to diagnose and monitor your disease involve your blood glucose level. There are different types of blood glucose tests, and it might be confusing to see them all. Listed below are the tests most commonly used to check your blood glucose level, with an explanation of what each one is for and how the test can be helpful to you.
Fasting blood sugar (FBS)
FBS checks the level of glucose in your blood after you haven’t eaten for some time. Normally, there should be a lower amount of glucose since your body is not taking additional glucose from food and your cells are using up the glucose in your blood for fuel. This test is used by your doctor to diagnose diabetes.
Before blood is drawn for your FBS, you will be asked not to eat or drink anything for 8 hours. Since you don’t take any food or drink while you are asleep, the most convenient time to have this test done is first thing in the morning, before breakfast.
A normal FBS result is 70 to 99 milligrams (mg) of glucose per deciliter (dl), or 3.9-5.5 mmol per liter (L). If your FBS result is 100 to 125 mg/dL (5.6 to 6.9 mmol/L), you have impaired fasting glucose. An impaired fasting glucose result is also known as pre-diabetes—you do not have diabetes yet, but your body may already have some difficulty with the way it uses and controls glucose.
If your FBS result is 126 mg/dL (7.0 mmol/L) or higher, your doctor will likely ask for another FBS test at a later time. If the result is still elevated, you have diabetes.
Oral glucose tolerance test (OGTT)
OGTT monitors how your blood glucose level changes over time. This test is commonly used to check for diabetes in pregnant women, a condition known as gestational diabetes. However, it can also be used to diagnose pre-diabetes and diabetes.
Several samples of blood are drawn at different times. Just like with the FBS test, you will be asked not to eat or drink anything for 8 hours. After the first sample of blood is drawn, you will be given a sugar solution to drink. Blood may then be drawn soon after. Samples of blood will also be taken 1, 2 , and 3 hours after you drink the sugar solution.
Normally, the blood glucose level taken before you drink the sugar solution should be 95 mg/dL (5.3 mmol/L). The next blood glucose level should be the highest (usually 180 mg/dL, or 10.0 mmol/L). After that, your blood glucose levels should gradually start decreasing. If two or more blood glucose levels are higher than the acceptable values, you will be diagnosed with gestational diabetes.
Post-prandial blood sugar
Post-prandial blood sugar is a test that measures your blood sugar two hours after you eat. Normal values for this test range from 70 to 145 mg/dL (3.9-8.1 mmol/L).
Random blood sugar (RBS)
Random blood sugar (RBS) may also be called capillary blood glucose (CBG). With this test, blood may be drawn any time of the day. You do not need to prepare by refraining from eating or drinking, or by taking in any sugar solution. The RBS test monitors how well your blood glucose level is controlled throughout the day. Normally, the results should be 70-125 mg/dL (3.9-6.9 mmol/L). Even if taken at different times, each result should not vary much from each other.
Aside from being used to monitor patients in the hospital, the RBS test can be used by people with diabetes to check their glucose levels at home. There are many devices that allow you to rapidly and accurately check your RBS yourself. This is especially helpful to see if you develop a complication of diabetes treatment known as hypoglycemia (low blood glucose). If your RBS result at home is less than 70mg/dL and you are experiencing symptoms such as dizziness or weakness, you may need to seek medical attention.
Glycosylated haemoglobin (HbA1C)
Glycosylated haemoglobin (HbA1C) is not used to diagnose diabetes. Rather, your health care provider will use this test to see if your blood glucose level is being adequately and consistently controlled. With the HbA1C test, your doctor can see if the treatment for your diabetes is working. It shows a general picture of your blood sugar level over the past 2 to 3 months. Normal values for this test range from 5% to 7%. If your HbA1C levels are within normal range, this means that your blood glucose level is well controlled and that you have a decreased risk of developing complications from diabetes.
Urinalysis
Blood tests are not the only way to see if your diabetes is being managed well. If you have too much glucose in your blood, the glucose may spill over into your urine. Glucose in the blood is a sign that your diabetes is not being controlled well.
One of the complications of diabetes is kidney disease, and urine tests are also used to see if your kidneys are functioning well, or if you have developed complications.
Sometimes, people with diabetes produce chemicals called ketones. When ketones are being produced by your body, this means that your glucose is really not being controlled well. Ketones may be found in the urine.