1079. Glucose (serum)

Glucose is the main source of energy for the body's cells. It is obtained from food and is partially produced in the body during metabolism. A glucose test helps assess blood sugar levels. High blood glucose levels can be a sign of diabetes, a serious condition that can cause tissue and organ damage if left untreated. Low blood glucose levels are called hypoglycemia. Hypoglycemia is often caused by diabetes medications, but can also result from certain medical conditions unrelated to diabetes or other medications.

Glucose is essential for the normal functioning of all organs and systems of the body. Its level in the blood is constantly controlled by hormones. The main one is insulin, which helps cells absorb sugar. At the same time, there are hormones that increase blood glucose levels. Their balance ensures the maintenance of glucose concentration within physiological limits.

A disruption of this balance sometimes indicates the development of endocrine or metabolic-related diseases. This is why a blood sugar test is one of the basic laboratory tests used for screening, diagnosis, and treatment monitoring, and it helps assess the state of carbohydrate metabolism, detect diabetes and other disorders in a timely manner. Monitoring blood sugar levels is an important part of disease prevention and maintaining health. Timely diagnosis, regular examinations, and monitoring of indicators help prevent complications and maintain good well-being.

Why is glucose needed and what does the test show?

A glucose test allows determining how correctly the body absorbs and uses energy from food. Determining glucose concentration is one of the basic laboratory tests used in the diagnosis of prediabetes, diabetes mellitus, and hypoglycemia (low blood sugar levels). For screening, diagnosis of diabetes mellitus and prediabetes (a condition in which blood glucose levels do not meet the criteria for diabetes but are too high to be considered normal), this test is recommended to be performed together with glycated hemoglobin.

A blood glucose test is often prescribed during preventive medical examinations, as well as when symptoms appear that may indicate increased or decreased blood sugar levels. The test also helps evaluate the effectiveness of treatment in people who already have diabetes.

What is the normal blood sugar level?

A doctor evaluates whether blood sugar levels are normal according to evidence-based medicine protocols.

According to the protocol of the Ministry of Health of Ukraine*, the criteria for prediabetes include:

• fasting blood glucose 5.6–6.9 mmol/L;

or

• blood glucose 2 hours after an oral glucose tolerance test (OGTT) with 75 g of glucose (this test measures the amount of glucose in the blood after an overnight fast and then after drinking a sweet beverage. A glucose tolerance test usually requires more than one blood draw over several hours) 7.8–11.0 mmol/L;
• HbA1C (glycated hemoglobin) 5.7-6.4%.

Diagnostic criteria for diabetes mellitus:

fasting blood glucose ≥7.0 mmol/L (fasting is defined as the absence of calorie intake for at least 8 hours)

or

blood glucose 2 hours after an oral glucose tolerance test (OGTT) with 75 g of glucose ≥11.1 mmol/L

or

HbA1C (glycated hemoglobin) ≥6.5%

or

random blood glucose concentration** ≥11.1 mmol/L in a person with classic symptoms of elevated blood sugar.

The 75 g glucose test measures the amount of glucose in the blood after an overnight fast and then after drinking a sweet beverage. A glucose tolerance test usually requires more than one blood draw over several hours.

For diagnosis, abnormal results from two test measurements from the same sample or from two separate test samples are required. Special measuring devices (glucometers) and test strips should not be used to establish a diagnosis of diabetes mellitus.

**This test measures the amount of glucose in the blood, but it can be performed at any time of the day, regardless of whether the person has recently eaten or not. People diagnosed with diabetes can also check their glucose levels throughout the day at home using a finger-prick blood sample and a glucometer.

High blood glucose level

Causes of increased levels may include:

• diseases of the pancreas (pancreatitis, tumors);
• use of medications (glucocorticoids, some diuretics, oral contraceptives), endocrine diseases (Cushing’s syndrome, acromegaly, hyperthyroidism);
• acute conditions of the body (physical trauma, myocardial infarction, or stroke).

An increased glucose level is called hyperglycemia and requires additional evaluation. Most often, high blood glucose levels are associated with impaired insulin production or decreased sensitivity of cells to insulin. This may indicate prediabetes or diabetes.

Possible symptoms include:

• constant thirst;
• dry mouth;
• frequent urination;
• rapid fatigue;
• drowsiness;
• blurred vision.

Sometimes elevated blood sugar does not cause noticeable symptoms for a long time, therefore regular blood glucose testing is important for prevention and early diagnosis. Monitoring this indicator and maintaining its level within the target range helps reduce the risk of complications affecting the cardiovascular system, kidneys, and organs of vision in people who already have diabetes.

Low blood sugar level

Low glucose levels are called hypoglycemia. This condition occurs when the body does not receive enough glucose to provide cells with energy.

Hypoglycemia is often associated with diabetes treatment. However, other medications and various diseases (many of which are rare) can cause low blood sugar levels in people who do not have diabetes.

Other possible causes include prolonged fasting, excessive physical activity, alcohol intoxication, long intervals between meals, or certain endocrine diseases.

The main symptoms of decreased blood sugar levels include:

• weakness;
• trembling;
• dizziness;
• increased sweating;
• feeling of hunger;
• rapid heartbeat.

Severe hypoglycemia can lead to loss of consciousness and seizures.

Hypoglycemia requires immediate treatment, which involves rapidly restoring blood glucose levels to normal with food or beverages high in sugar or with medications.

In cases of pronounced symptoms or significant deviations in results, a doctor may recommend additional diagnostic tests to determine the causes of the changes. Test results should be evaluated taking into account the person’s overall condition and other laboratory indicators.

Glucose testing is required both for preventive health monitoring and when symptoms of carbohydrate metabolism disorders appear (frequent urination, excessive hunger, tingling or loss of sensation in the hands or feet, blurred vision, unexplained weight loss, constant thirst, dry skin, poor wound healing).

Testing for diabetes and prediabetes is recommended for asymptomatic adults with the following risk factors:*

• Overweight or obesity (BMI ≥ 25 kg/m² or ≥ 23 kg/m² in people of Asian descent) and one or more additional risk factors:
  • having a first-degree relative with diabetes;
  • belonging to ethnic groups with an increased risk of developing diabetes (e.g., African Americans, Hispanics, Asians);
  • presence of cardiovascular disease (CVD);
  • high blood pressure or high cholesterol;
  • women with PMOS (polyendocrine metabolic ovarian syndrome);
• physical inactivity;
• other clinical conditions associated with insulin resistance (e.g., severe obesity, etc.);
• people with prediabetes;
• women diagnosed with gestational diabetes;
• people living with HIV.

For people not in the risk group, testing should begin at age 35.

* UNIFIED CLINICAL PROTOCOL FOR PRIMARY AND SPECIALIZED MEDICAL CARE FOR TYPE 2 DIABETES MELLITUS IN ADULTS. Order of the Ministry of Health of Ukraine dated July 24, 2024, No. 1300

Regular blood sugar testing helps monitor the body's condition, assess the effectiveness of treatment, and promptly identify potential complications.

• Venous blood

In order to exclude factors that may affect the test results, we recommend to follow the preparation rules: