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Diagnostic Tests 2023

Diabetes tests: 4 exams that confirm the diagnosisóstic

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Diabetes tests: 4 exams that confirm the diagnosisóstic
Diabetes tests: 4 exams that confirm the diagnosisóstic

Confirmation of diabetes is made by checking the results of several laboratory tests that assess the amount of glucose circulating in the blood: fasting blood glucose test, capillary blood glucose test, glucose tolerance test (OGTT) and the glycated hemoglobin test.

Exams that assess the amount of glucose in the blood are requested by the doctor when the person has someone in the family with diabetes or when they present characteristic symptoms of the disease, such as constant thirst, frequent urge to urinate or weight loss for no reason apparent please. However, these tests can be ordered without risk of diabetes, just for the doctor to check the general state of he alth of the person. Know how to recognize the symptoms of diabetes.


Reference values

Normal blood glucose values vary by test type and may also vary by laboratory due to analysis technique. In general, the values of the tests for diabetes are indicated in the following table:

Exam Result Diagnostics

Fasting blood glucose (glucose)

Less than 99 mg/dL Normal
Between 100 and 125 mg/dL Pre-diabetes
Greater than 126 mg/dL Diabetes

Capillary blood glucose test (2 hours after a meal)

Less than 200 mg/dL Normal
Greater than 200 mg/dL Diabetes

Glycated Hemoglobin

Less than 5.6% Normal
Between 5, 7 and 6, 4% Pre-diabetes
Greater than 6.5% Diabetes
Glucose Tolerance Test (GTT) Less than 140 mg/dL Normal
Between 141 and 199 mg/dL Decreased glucose tolerance
Greater than 200 mg/dL Diabetes

Through the results of these tests, the doctor is able to identify pre-diabetes and diabetes and, thus, indicate the best treatment for the person in order to avoid complications related to the disease, such as ketoacidosis and retinopathy, for example.

To know now your risk of developing this disease, select the test performed and enter your result:

Main tests for diabetes

1. Fasting glucose test

This test is the most requested by the doctor and the analysis is done from the collection of a blood sample after fasting for at least 8 hours or according to the doctor's recommendation. If the value is above the reference value, the doctor may request other tests, especially the glycated hemoglobin test, which indicates the average amount of glucose in the three months prior to the test. In this way, the doctor can assess whether the person is at risk or has the disease.

In case the result of the fasting blood glucose test indicates pre-diabetes, lifestyle changes are necessary, such as changing the diet and practicing physical activity to prevent the onset of the disease. However, when the diagnosis of the disease is confirmed, in addition to lifestyle changes, it is also necessary to take medication and, in some cases, insulin.

Learn how to eat for pre-diabetes.

2. Glucose Tolerance Test (OGTT)

The glucose tolerance test, also known as the glycemic curve test, is performed with the objective of evaluating the functioning of the organism in the face of various glucose concentrations. To do this, three blood glucose measurements are taken: the first is carried out on an empty stomach, the second 1 hour after ingesting the sugary drink, dextrosol or garapa, and the third 2 hours after the first measurement.

In some cases, 4 blood collections can be performed until 2 hours of drinking are completed, with collections being performed at 30, 60, 90 and 120 minutes after consumption of the sugary drink.

This test is important to help in the diagnosis of diabetes, pre-diabetes, insulin resistance and pancreatic alterations, in addition, it is very requested in the investigation of gestational diabetes.

3. Capillary blood glucose test

The capillary blood glucose test is the finger prick test, which is performed using a rapid glucose measuring machine, which can be found in pharmacies and gives the result immediately. You don't need to fast for this test and can be done at any time of the day. This test is mostly used by people who already have a diagnosis of pre-diabetes or diabetes in order to control glucose levels throughout the day.

4. Glycated hemoglobin test

The glycated hemoglobin or glycosylated hemoglobin test is performed from the collection of a fasting blood sample and provides information on the amount of glucose circulating in the blood in the last 3 months before the test is performed. This is because the glucose circulating in the blood binds to hemoglobin and remains bound until the red blood cell's lifespan ends, which is 120 days.

Glycated hemoglobin can also be used to assess disease improvement or worsening, and the higher the value, the greater its severity and the risk of complications. Understand what it is for and how to understand the result of the glycated hemoglobin test.

Who should take these exams

It is advised that all people with symptoms of diabetes undergo tests to confirm the disease, as well as pregnant women, to prevent complications linked to excess blood sugar during pregnancy. In addition, people who are losing a lot of weight for no apparent reason, especially children and teenagers, also need to have blood glucose tests to diagnose the possibility of type 1 diabetes.

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