Fasting glucose, or fasting glucose, is a blood test that measures the level of glucose in the bloodstream and needs to be done after an 8 to 12 hour fast, or according to the doctor's guidance, without consumption of any food or drink, except water. This test is widely used to investigate the diagnosis of diabetes, and to monitor the blood sugar levels of people who are diabetic or at risk for this disease.
In addition, in order to obtain more reliable results, this test can be ordered in conjunction with others that also evaluate these changes, such as the oral glucose tolerance test (or TOTG) and glycated hemoglobin, especially if there is a change in the glucose test In fasting. Learn more about the tests that confirm diabetes.
Fasting blood glucose reference values
The reference values for fasting blood glucose are:
- Normal fasting glucose: less than 99 mg / dL; Altered fasting glucose: between 100 mg / dL and 125 mg / dL; Diabetes: equal to or greater than 126 mg / dL; Low fasting glucose or hypoglycemia: equal to or less than 70 mg / dL.
To confirm the diagnosis of diabetes, when the glycemia value is equal to or greater than 126 mg / dl, it is necessary to repeat the test another day, since at least 2 samples are recommended, in addition to the need to perform the glycated hemoglobin and the oral glucose tolerance test.
When the test values are between 100 and 125 mg / dL, it means that the fasting blood glucose is altered, that is, the person has a pre-diabetes, a situation in which the disease has not yet set in, but there are an increased risk of developing. Learn more about what it is and how to treat prediabetes.
The examination of fasting blood glucose in pregnancy is part of the prenatal routine and can be done at any trimester of pregnancy, but the reference values are different. Thus, for pregnant women, when fasting blood glucose is above 92 mg / dL, it may be a case of gestational diabetes, however, the main diagnostic test for this condition is the glycemic curve or TOTG. Find out what it means and how the glycemic curve test is done.
How to prepare for the exam
The preparation of the fasting blood glucose test includes not eating any food or drink that contains calories for at least 8 hours, and should not exceed 12 hours of fasting.
It is recommended to keep the usual diet in the week prior to the exam and, in addition, it is important not to consume alcohol, avoid caffeine and do not exercise rigorously the day before the exam.
Who should take the exam
This test is usually requested by doctors to track the presence of diabetes mellitus, a disease that causes an increase in blood glucose, or to monitor blood glucose levels for those who are already being treated for this disease.
This investigation is usually done for all people over 45 years old, every 3 years, but it can be done in younger people or in less time, if there are risk factors for diabetes, such as:
- Diabetes symptoms such as excessive thirst, excessive hunger and weight loss; Family history of diabetes; Sedentary lifestyle; Obesity; Low (good) HDL cholesterol; High blood pressure; Coronary heart disease, such as angina or infarction; History of gestational diabetes or childbirth with macrosomia; use of hyperglycemic medication, such as corticosteroids and beta-blockers.
In cases of impaired fasting blood glucose or impaired glucose tolerance detected in previous tests, it is also recommended to repeat the test annually.
