Blood Glucose (Sugar)

Also known as: Blood Sugar, Fasting Blood Sugar, FBS, Fasting Blood Glucose, FBG, Fasting Plasma Glucose, FPG, Glucose, GLU, Oral Glucose Tolerance Test, OGTT, GTT

What is Glucose?

Glucose is a vital source of energy for the cells of the body. It is formed as a result of the digestion of carbohydrates (rice, pasta, bread, potatoes, etc.). The digestive system of the body with the help of bile and enzymes converts carbohydrates into glucose (blood sugar). Then glucose is absorbed through the small intestine into the blood and then spreads throughout the body, providing the body with the energy necessary for all types of life activities: from performing simple movements to brain function.

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It is extremely important to maintain the level of glucose (sugar) in the blood within the normal range. To do this, there are two hormones, insulin, and glucagon, which directly regulate the level of glucose in the blood. The human body is adapted to maintain an ideal sugar level, retaining an excess amount of glucose in the liver and muscles in the form of glycogen. When the glucose level in the body drops, glycogen is converted by glucagon into glucose. Glucose is released into the bloodstream and other cells can use it for energy.

Blood Glucose (Sugar)

Insulin is a hormone secreted by the pancreas. When the blood glucose levels rise, the pancreas begins to produce insulin. Insulin then signals cells throughout the body to absorb glucose from the bloodstream and the blood sugar levels go down.

In addition to insulin and glucagon, other hormones also play an important role in glucose metabolism. Corticosteroids, thyroxine, adrenaline increase glucose and are called contrainsular hormones.

Normal Blood Sugar Levels

Low level of blood glucose is usually determined in the morning before a meal (fasting glucose level) and after intense physical activity. The glucose level rises within an hour or two after meals and then decreases again. If at some stage the sugar level goes beyond the normal range, this may indicate health problems. Elevated blood sugar is called hyperglycemia, and low blood sugar is called hypoglycemia.

Blood glucose levels can be measured in mmol/L (millimoles per liter) and in mg/dL (milligrams per deciliter).

According to American Diabetes Association (ADA), normal fasting plasma glucose (FPG) should be less than 100 mg/dL (5.6 mmol/L). If your blood glucose levels are ≥ 100 mg/dL (5.6 mmol/L) but < 126 mg/dL (7.0 mmol/L), you may be diagnosed with prediabetes. Fasting blood sugar ≥ 126 mg/dL (7 mmol/L) indicates the presence of diabetes.

If the test results are close to the margins of the diagnostic threshold, it is advisable to repeat the test in 3-6 months.

Blood Sugar Level in Pregnancy

Normal fasting plasma glucose levels during pregnancy should be below 92 mg/dL (5.1 mmol/L). If a pregnant woman has blood sugar level greater than or equal to 92 mg/dL (5.1 mmol/L) but less than 126 mg/dL (7.0 mmol/L) gestational diabetes (GDM) may be diagnosed. Fasting blood sugar >= 126 mg/dL (7 mmol/L) indicates the presence of diabetes.

How to Check Blood Sugar Levels

There are several ways to check your blood sugar level:

  • Fasting Plasma Glucose (FPG) test, also known as Fasting Blood Sugar. A blood sample is taken after fasting for at least eight hours.
  • Oral Glucose Tolerance Test (OGTT, GTT) measures the blood sugar level after taking a specific amount of glucose.
  • Random Glucose test (Random Blood Sugar). The blood sugar level is measured regardless of when you last ate.

High Blood Sugar

Sometimes the process of regulating blood glucose does not work properly. If the pancreas doesn't produce enough insulin or the cells don't respond to the effects of insulin the glucose levels in the blood stay elevated (hyperglycemia), which may cause complications. The most common disease that causes blood sugar problems is diabetes.

  • Type 1 diabetes. The body lacks insulin. Type 1 diabetes is considered an autoimmune disease, as a result of which the immune system attacks and destroys pancreatic insulin-producing cells. Glucose cannot enter the cells without insulin, and the level of sugar in the blood does not decrease. In this disease, you must take insulin every day.
  • Type 2 diabetes. The body produces insulin, but the cells do not respond to it properly. Thus, glucose is less able to enter the cells and supply them with energy. This is called insulin resistance. The pancreas still detects high blood sugar levels, and it has to produce more and more insulin to move glucose into the cells. Over time, the pancreas is damaged and cannot produce enough insulin to maintain proper blood sugar levels.
  • Gestational diabetes develops in some women during pregnancy. This disease is characterized by an elevated blood sugar level, which was first detected during pregnancy, but the sugar level is not high enough to make a diagnosis of diabetes. Hormones associated with pregnancy can affect insulin. This condition usually disappears after childbirth. However, if you had gestational diabetes, you have an increased risk of developing type 2 diabetes.
  • Impaired fasting glucose (IFG) or impaired fasting hyperglycemia. Fasting blood glucose is above normal, but not yet high enough to diagnose diabetes.
  • Impaired glucose tolerance (IGT). The level of glucose in the blood is increased 2 hours after an oral glucose tolerance test, but not high enough to make a diagnosis of diabetes.

Impaired fasting glucose and impaired glucose tolerance are also called prediabetes. Without a lifestyle change, prediabetes is likely to develop type 2 diabetes. But with prediabetes, the damage your blood vessels, heart, and kidneys may already be starting.

It is important to be able to recognize and treat hyperglycemia (high blood sugar) because if untreated, it can lead to serious health problems. Elevated blood sugar over time can lead to vascular damage, and also increases the risk of developing:

  • heart disease, heart attack, stroke
  • kidney disease
  • nerve damage
  • diabetic retinopathy or diabetic eye disease (damage to the back of the eye (retina)).

The presence of diabetes doubles the risk of developing a wide range of vascular diseases, regardless of other common risk factors. In people without diabetes, fasting blood glucose is moderately and nonlinearly associated with the risk of vascular disease [1].

Low Blood Sugar

Low blood sugar is called hypoglycemia. Low blood sugar is often seen in people with diabetes, especially if they take insulin, and is rare in healthy people.

Possible causes of hypoglycemia are:

  • taking too much diabetes medication, especially too much insulin
  • malnutrition or fasting
  • alcohol abuse
  • some medications (for example, quinine) can lower blood sugar levels
  • kidney disease, hepatitis
  • endocrine disorders, such as adrenal gland deficiency.

Comprehensive Metabolic Panel (CMP) Interpretation