Glucose

The blood sugar concentration or blood glucose level is the amount of glucose (sugar) present in the blood of a human. The body naturally tightly regulates blood glucose levels as a part of metabolic homeostasis. Most of the cells in the body use glucose along with amino acids and fats for energy. It's the main source of energy for the brain ensuring its proper work [1].

Glucose mainly comes from foods rich in carbohydrates, like bread, potatoes, and fruits. During food digestion in the stomach (acids and enzymes break it down into tiny pieces), glucose is released. After that, it's absorbed in the intestines. Glucose is transported from the intestines (in other cases from the liver [Note 1]) to other tissues in the body via the bloodstream by insulin.

Insulin is a hormone produced in the pancreas that moves glucose from the blood into the cells for energy and storage. Beta cells in the pancreas monitor blood sugar level every few seconds. When the blood glucose rises after eating, the beta cells release insulin into the bloodstream.

Note 1: After a body has used the energy required, the leftover glucose is stored in the form of glycogen in the liver and muscles (approximately day supply).

After few hours of fasting, blood glucose level drops. The pancreas stops churning out insulin. Alpha cells in the pancreas begin to produce a different hormone called glucagon. It signals the liver to break down stored glycogen and turn it back into glucose. The liver can also make its own glucose using a combination of waste products, amino acids, and fats [1,2].

Abnormalities. Disorders or diseases caused or related.

Glucose levels are usually lowest in the morning, before the first meal of the day (termed "the fasting level"), and rise after meals for an hour or two by a few millimolar. If glucose results are not normal, it doesn't necessarily mean a person has a medical condition needing treatment. High stress and certain medicines can affect glucose levels.

People with higher-than-normal levels of glucose in their blood either don't have enough insulin to move it through or their cells don't respond to insulin as well as they should.

A persistently high level of glucose is referred to as hyperglycaemia [3].

If blood sugar levels remain too high the body suppresses appetite over the short term. Long-term hyperglycaemia causes many of the long-term health problems including heart disease, eye, kidney, and nerve damage.

Besides diabetes, high glucose levels may also be a sign of:

·        Kidney disease

·        Hyperthyroidism

·        Pancreatitis

·        Pancreatic cancer

Symptoms of high blood glucose levels include:

·        Increased thirst

·        More frequent urination

·        Blurred vision

·        Fatigue

·        Wounds that are slow to heal

A persistently low levels of glucose are referred to as hypoglycaemia [4].

In healthy individuals, blood glucose-regulating mechanisms are generally quite effective, and symptomatic hypoglycaemia is generally found only in diabetics using insulin or other pharmacological treatment. Hypoglycaemia is most often caused by drugs taken to control diabetes. Much fewer common causes of hypoglycaemia include other drugs, critical illness or organ failure (e.g., hypothyroidism, liver disease, etc.), a reaction to carbohydrates (in susceptible people), an insulin-producing tumour in the pancreas, and some types of bariatric (weight loss) surgery.

Symptoms of extreme hypoglycaemia (below 40 mg/dl or 2.2 mmol/l) may include impaired mental functioning, irritability, shaking, twitching, weakness in arm and leg muscles, pale complexion, sweating and confusion. Extremely serious consequences of insufficient glucose (below 15 mg/dl or 0.8 mmol/l) are loss of consciousness and seizures, up to coma [4]

1.       Wasserman DH (January 2009). "Four grams of glucose". American Journal of Physiology. Endocrinology and Metabolism. 296 (1): E11–21. doi:10.1152/ajpendo.90563.2008. PMC 2636990. PMID 18840763.

2.       University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Glucose (Blood) [cited 2017 Jul 21]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=glucose_bloodLab Tests Online [Internet]. American Association for Clinical Chemistry; c2001–2017. Glucose Tests: The Test [updated 2017 Jan 16; cited 2017 Jul 21]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/glucose/tab/test/

3.       Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2017. Diabetes Mellitus (DM) [cited 2017 Jul 21]; [about 2 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/diabetes-mellitus-dm-and-disorders-of-blood-sugar-metabolism/diabetes-mellitus-dm

4.       Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2017. Hypoglycemia (Low Blood Sugar) [cited 2017 Jul 21]; [about 2 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/diabetes-mellitus-dm-and-disorders-of-blood-sugar-metabolism/hypoglycemia