A significant portion of the daily food intake consists of carbohydrates. Glycogen and starch make up the majority of carbohydrates. Digestion begins with salivary amylase in the mouth. It continues in the stomach and small intestines. When digestion is finished, glucose, galactose and fructose are released from the carbohydrates we take.
Glucose passes into the blood and transports it to the target organs. In target organs, it passes into the cells through the proteins called GLUT in the cell membranes. Energy and other useful molecules are released by breaking down glucose again in the cell. The breakdown of glucose is called glycolysis. The energy that emerges after the breakdown of glucose is used to maintain the functions of cells and organs. The method of breaking down glucose changes according to the oxygen capacity of the cell where the glucose is present, and the amount of energy produced also changes. Other molecules produced by the breakdown of glucose are mostly lactate and pyruvate.
Excess glucose in the body is converted into glycogen and stored for storage. It is usually stored in the liver and muscles. While the muscles use the glycogen they store themselves, the glycogen stored in the liver will be used by sending it back to the cells that the body needs.
When there is not enough glucose in the blood or cells, some other non-carbohydrate molecules in the body are processed and glucose is produced. In this way, the glucose needs of the cells are met. This process is also called gluconeogenesis. Gluconeogenesis takes place mostly in the liver and kidneys. For example, in the fasting state, the body produces glucose, which is necessary for the brain and erythrocytes, by this mechanism. Most of this process is done in the liver. If the fasting period is prolonged and the liver is not enough, the kidneys come into play. Various enzymes take part in many different stages of these mechanisms. Glucose is produced from many different molecules. The deficiencies of these enzymes also cause various diseases.
The balance of glucose in our body is controlled by essential enzymes and hormones such as insulin, glucagon, acetyl coenzyme A and alanine. Disruptions in these factors also cause many diseases.
The body’s inability to take glucose from the mouth, to use the glucose it receives, or to be unable to produce from the inside causes vital organs to fail. In severe disorders, it can cause coma and even death.
Blood glucose level is tried to be kept at certain levels thanks to many integrated mechanisms. Especially the liver and pancreas are the main organs in maintaining this balance. Hormones, especially insulin, glucagon, epinephrine, cortisol, and growth hormone, also regulate blood glucose.
If the blood glucose is within the reference range, it is called normoglycemia , if it is above the reference range, it is called hyperglycemia , and if it is below the reference range, it is called hypoglycemia .
How is blood sugar (glucose) measured?
Blood glucose assessment can be measured by checking the fasting blood glucose level and the postprandial blood glucose level. In both cases, it is done by taking a blood sample.
Fasting blood glucose: It is the blood glucose level measured after 8-14 hours of fasting. Its normal limits are 74-100 mg/dL. In some centers, the upper limit may vary up to 115mg/dL.
Postprandial blood glucose: It is the blood glucose level measured 2 hours after a meal. It should be below 140 mg/dL in a healthy adult.
In some cases, it may be necessary to check blood glucose at any time of the day. Random blood glucose detection can be used for patient follow-up or for the evaluation of immediate symptoms.
Sometimes, the body’s response to glucose can be evaluated as part of further investigations and diagnosis. Two hours after the patient is given a certain amount of glucose, blood glucose is measured. This is also called an oral glucose tolerance test.
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Why is a blood glucose test done?
Blood glucose tests are performed in all cases where the body’s blood sugar mechanism is suspected. This may also be for the purpose of examining any symptoms or monitoring the progress of a disease. As the blood glucose level can deteriorate in basic diseases such as diabetes, it can also become abnormal as a symptom of many diseases or conditions other than diabetes. In the normal rhythm of the body, blood glucose levels may be low or high at certain times. Every low or high may not indicate a disease. The result obtained in a single measurement may not be sufficient to make a decision. Sometimes repeated measurements and evaluations in conjunction with other tests are needed. All these situations may need to be interpreted and evaluated separately by your physician.
The most common causes of high blood glucose (hyperglycemia):
- Diabetes disease
- Improper diet
- Hepatocellular diseases
- Chronic diseases
- Prolonged physical inactivity
- Nutritional disorders
- Kidney diseases
- Alcoholism
- Primary hyperaldosteronism
- Celebral hemorrhage
- Myocardial infarction
- Surgical stress
- Stress due to febrile illness
- Acromegaly
- Cushing’s syndrome
- Adrenocortical hyperfunction
- Long-term steroid therapy
- Islet cell tumors
- Uremia
- After gastric surgery
- Medicines
The most common causes of low blood glucose (hypoglycemia):
- Reactive hypoglycemia
- Emotional disorders
- Diabetes mellitus
- Alimentary hypoglycemia (after gastric surgery)
- Hereditary fructose intolerance
- Fasting hypoglycemia
- Pancreatic islet cell disease
- Glucagon deficiency
- Extrapancreatic tumors
- Mesothelioma
- Fibroma
- Fibrosarcoma
- Leiomyosarcoma
- Liver diseases
- Glycogen storage disease
- Galactosemia
- Fulminant hepatitis
- Toxic hepatic necrosis
- Cholangitis
- Cirrhosis
- Leucine sensitivity
- Alcohol-induced hypoglycemia
- Malnutrition and Kwashiorkor
- Endocrine disorders
- Addison’s disease
- Hypopituitarism
- Drug-induced hypoglycemia
- Salicylate intake
- Monoaminooxidase inhibitors
- Barbutirates
- Insulin
- Sulfonylurea
- Some other drugs