General Practice 2022

Glycemia: what é, how to measure and reference valuesê

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Glycemia: what é, how to measure and reference valuesê
Glycemia: what é, how to measure and reference valuesê

Glycemia is the term that refers to the amount of glucose, better known as sugar, in the blood that arrives through the ingestion of foods that contain carbohydrates, such as cake, pasta and bread, for example. The concentration of glucose in the blood is controlled by two hormones, insulin, which is responsible for reducing sugar in the bloodstream, and glucagon, which has the function of increasing glucose levels.

There are several ways to measure blood glucose levels through blood tests, such as fasting glucose and glycated hemoglobin, or through easy-to-use blood glucose meters and devices that the person can use.

The blood glucose reference values ​​should ideally be between 70 to 100 mg/dL fasting and when it is below this value it indicates hypoglycemia, which causes symptoms such as drowsiness, dizziness and even fainting.Hyperglycemia, on the other hand, is when fasting blood glucose is above 100 mg/dL and may indicate type 1 or type 2 diabetes, which if not controlled can cause complications such as vision problems and diabetic foot. Know other symptoms of diabetes.

How to measure blood glucose

Blood glucose refers to the concentration of glucose in the blood and can be measured in several ways, such as:

1. Capillary blood glucose

Capillary blood glucose is a test that is performed through the prick of a finger and then the analysis of the drop of blood on a tape connected to a device called a glucometer. Currently, there are several models of different brands of glucometer, it is found for sale in pharmacies and can be performed by anyone, as long as they are previously instructed.

This type of test allows people who have diabetes to have greater control over blood glucose levels, preventing hypoglycemia episodes due to the use of insulin, helping to understand how food, stress, emotions and exercise physical changes alter blood glucose levels and also helps to set the correct dose of insulin to be administered.See how to measure capillary blood glucose.

2. Fasting blood glucose

Fasting blood glucose is a blood test performed to check blood glucose levels and should be taken after a period of not eating or drinking anything other than water for at least 8 hours or as directed by your doctor.

This exam helps the general practitioner or endocrinologist to diagnose diabetes, however, more than one sample must be collected and more exams, such as glycated hemoglobin, may be recommended for the doctor to close the diagnosis of diabetes. Fasting blood glucose may also be performed for the doctor to assess whether treatment for diabetes is working or to monitor other he alth problems that alter blood glucose levels.

3. Glycated hemoglobin

Glycated hemoglobin, or HbA1c, is a blood test performed to assess the amount of glucose bound to hemoglobin, a component of red blood cells, and refers to the blood glucose history over 120 days, as it is this period of red blood cell life and the time it is exposed to sugar, forming glycated hemoglobin, and this test is the most used method to diagnose diabetes.

The normal reference values ​​of glycated hemoglobin should be less than 5.7%, however, in some cases, the glycated hemoglobin result may be altered because of some factors such as anemia, drug use and blood diseases, so before performing the exam the doctor will analyze the person's he alth history.

4. Glycemic curve

The glycemic curve, also known as the glucose tolerance test, consists of a blood test in which fasting blood glucose is checked and 2 hours after taking 75 g of glucose by mouth. In the 3 days before the exam, the person needs to eat a diet rich in carbohydrates, such as breads and cakes, for example, and then fast for 12 hours.

Furthermore, it is important that the person has not had coffee and has not smoked for at least 24 hours before performing the exam. After the first blood sample is collected, the person will ingest the glucose and then rest for 2 hours to collect blood again.After the exam, the result takes between 2 to 3 days to be ready, depending on the laboratory and normal values ​​should be below 100 mg/dL fasting and 140 mg/dL after ingestion of 75g of glucose. Better understand the result of the glycemic curve.

5. Postprandial blood glucose

Postprandial blood glucose is a test to identify blood glucose levels between 1 to 2 hours after a person has had a meal and serves to assess hyperglycemia peaks associated with cardiovascular risk or a problem of insulin release. Generally, this type of test is recommended by a general practitioner or endocrinologist to complement the fasting blood glucose test and normal values ​​should be below 140 mg/dL.

6. Blood glucose sensor on the arm

Currently, there is a sensor for checking blood glucose that is implanted in a person's arm and allows checking blood glucose levels without the need to prick the finger.This sensor is a round device with a very fine needle that is inserted into the back of the arm, it does not cause pain and does not generate discomfort, being widely used even for diabetic children, as it reduces the discomfort of having to pierce the finger.

In this case, to measure blood glucose, just bring the cell phone, or the specific device of the brand, to the arm sensor and then the scan will be done and the result will appear on the cell phone screen. The sensor must be changed every 14 days, but it is not necessary to perform any type of calibration, unlike the common capillary blood glucose device.

What is it for

Glycemia is indicated by a general practitioner or endocrinologist to check blood glucose levels and through this it is possible to detect certain diseases and conditions, such as:

  • Type 1 diabetes;
  • Type 2 diabetes;
  • Gestational diabetes;
  • Insulin resistance;
  • Changes in the thyroid;
  • Diseases of the pancreas;
  • Hormonal problems.

Glycemia control can also complement the diagnosis of Dumping syndrome, for example, which is a condition in which food passes quickly from the stomach to the intestine, leading to the appearance of hypoglycemia and causing symptoms such as dizziness, nausea and tremors. Learn more about Dumping Syndrome.

Often, this type of analysis is performed as a hospital routine in people who are hospitalized and who receive glucose saline or use drugs in the vein that can cause blood glucose to drop a lot or rise quickly.

What are the reference values

Exams to check capillary blood glucose are diverse and may vary according to the laboratory and tests used, but the results should generally have values ​​according to the table below:


After 2 hours of meals

Any time of day

Normal blood glucose Less than 100 mg/dL Less than 140 mg/dL Less than 100 mg/dL
Blood glucose altered Between 100 mg/dL to 126 mg/dL Between 140 mg/dL to 200 mg/dL Cannot set
Diabetes Greater than 126 mg/dL Greater than 200 mg/dL More than 200 mg/dL with symptoms

After checking the test results, the doctor will analyze a person's symptoms and may recommend other tests to check for possible causes of low or high blood glucose.To better understand your glucose test result, enter your results into the calculator below:

1. Low blood glucose

Low blood glucose, also called hypoglycemia, is a decrease in blood glucose levels, identified by values ​​below 70 mg/dL. Symptoms of this condition can be dizziness, cold sweat, nausea, which can lead to fainting, mental confusion and coma if not reversed in time, and this can be caused by medication use or insulin use in very high doses. See more about what can cause hypoglycemia.

What to do: hypoglycemia should be treated quickly, so if a person has milder symptoms, such as dizziness, you should offer a juice box or something sweet immediately. In the most serious cases, in which mental confusion and fainting occur, it is necessary to call the SAMU ambulance or take the person to an emergency, and offer sugar only if the person is conscious.

2. High blood glucose

High blood glucose, better known as hyperglycemia, occurs when blood sugar levels are too high because of eating too sweet and carbohydrate-based foods, which can lead to diabetes. This change usually does not cause symptoms, however, in cases where blood glucose is very high and for a long time, dry mouth, headache, drowsiness and frequent urge to urinate may appear. Check out why hyperglycemia occurs.

What to do: In in cases where diabetes is already diagnosed, the doctor usually recommends the use of hypoglycemic drugs, such as metformin, and injectable insulin. In addition, in some cases, hyperglycemia can be reversed through dietary changes, reducing the consumption of foods rich in sugar and pasta, and through regular physical activity. See in the video below which exercises are most recommended for those who have diabetes.

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