The causes of increase and decrease in glucose

With a number of conditions, the glucose level in the blood rises (hyperglycemia) or decreases (hypoglycemia).

Most often, hyperglycemia develops in patients with diabetes mellitus. The diagnosis of diabetes mellitus can be established with a positive result of one of the following tests:

• clinical symptoms of diabetes mellitus (polyuria, polydipsia and unexplained weight loss) and a random increase in plasma glucose ≥11.1 mmol / l (≥200 mg%), or:
• the fasting plasma glucose concentration (no intake of any food for at least 8 hours) ≥ 7.1 mmol / l (≥126 mg%), or:
• plasma glucose concentration after 2 hours after oral glucose loading (75 g glucose) ≥11.1 mmol / l (≥200 mg%).

Diagnostic criteria for diabetes mellitus and other categories of hyperglycemia, recommended by WHO (Report of WHO Consultation, 1999), are given in Table. 4-16. For epidemiological or screening purposes, one result of determining the fasting glucose concentration or 2 hours after oral glucose loading is sufficient. For clinical purposes, the diagnosis of diabetes mellitus should always be confirmed by repeated testing on the following day, except for cases of undoubted hyperglycemia with acute metabolic decompensation or obvious symptoms.

In accordance with the new recommendations, the following concentrations of glucose in plasma of fasting venous blood have diagnostic value (WHO recommends only using plasma venous blood test results for the diagnosis):

• the normal concentration of glucose in blood plasma on an empty stomach is up to 6.1 mmol / l (<110 mg%);
• the fasting plasma glucose concentration from 6.1 mmol / l (≥110 mg%) to 7 (<128 mg%) is defined as impaired fasting glycemia;
• the fasting plasma glucose concentration above 7 mmol / l (> 128 mg%) is regarded as a preliminary diagnosis of diabetes mellitus, which must be confirmed by the above criteria.

Diagnostic criteria for diabetes mellitus and other categories of hyperglycemia

Category	Glucose concentration, mmol / l
	Whole Blood		Blood plasma
	Venous	Capillary	Venous	Capillary
Diabetes:
On an empty stomach	> 6.1	> 6.1	> 7.0	> 7.0
120 minutes after taking glucose	> 10.0	> 11.1	> 11.1	> 12.2
Impairment of glucose tolerance:
On an empty stomach	<6.1	<6.1	<7.0	<7.0
120 minutes after taking glucose	> 6.7 and <10.0	> 7.8 and <11.1	> 7.8 and <11.1	> 8.9 and <12.2
Impaired fasting glycemia:
On an empty stomach	> 5.6 and <6.1	> 5.6 and <6.1	> 6.1 and <7.0	> 6.1 and <7.0
120 minutes after taking glucose	<6.7	<7.8	<7.8	<8.9

In addition to diabetes, hyperglycemia is possible in the following conditions and diseases: CNS damage, increased hormonal activity of the thyroid gland, cortex and adrenal medulla, pituitary gland; trauma and brain tumors, epilepsy, carbon monoxide poisoning, strong emotional and mental arousals.

Hypoglycemia can be caused by the following reasons.

• Prolonged fasting.
• Violation of absorption of carbohydrates (diseases of the stomach and intestines, dumping syndrome).
• Chronic liver diseases due to impaired synthesis of glycogen and reduction of the hepatic depot of carbohydrates.
• Diseases associated with the violation of secretion of the contrinsular hormones (hypopituitarism, chronic insufficiency of the adrenal cortex, hypothyroidism).
• Overdose or unjustified administration of insulin and oral hypoglycemic drugs. In patients with diabetes mellitus receiving insulin, the most severe hypoglycemic conditions, up to hypoglycemic coma, usually develop when eating disorders - skipping meals, as well as vomiting after eating.
• Light hypoglycemic conditions can occur in diseases that occur with the so-called "functional" hyperinsulinemia: obesity, type 2 diabetes mild. The latter is characterized by the alternation of episodes of moderate hyperglycemia and slight hypoglycemia 3-4 hours after ingestion, when the maximum effect of insulin secreted in response to alimentary load develops.
• Sometimes hypoglycemic conditions are observed in people with CNS diseases: widespread vascular disorders, acute pyogenic meningitis, tuberculosis meningitis, cryptococcal meningitis, encephalitis in epidemic parotitis, primary or metastatic soft-vein tumor, non-bacterial meningoencephalitis, primary amoebic meningoencephalitis.
• The most severe hypoglycemia (with the exception of cases of an overdose of insulin) is observed in organic hyperinsulinism due to insulinoma or hyperplasia of beta cells of pancreatic islets. In some cases, the glucose in the blood of patients with hyperinsulinism is less than 1 mmol / l.
• Spontaneous hypoglycemia in sarcoidosis.