What Is Blood Sugar? What Is Blood Glucose?

Date: Aug-24-2012Blood sugar or blood glucose refers to sugar that is transported through the bloodstream to supply energy to all the cells in our bodies. The sugar is made from the food we eat. The human body regulates blood glucose levels so that they are neither too high nor too low - maintaining a condition of stability or equilibrium in the blood's internal environment (homeostasis) is necessary for our bodies to function.

The use of the word "sugar" in "blood sugar" is a colloquial term, a misnomer. Glucose, one type of sugar, is the one in the bloodstream that feeds cells and matters to us.

Sugar is a simple, crystalline, edible carbohydrate and comes in a variety of forms, all of them sweet. Our body digests carbohydrates into glucose, a simple sugar that can easily convert to energy. The chemical formula for glucose is C6H12O6.

The human digestive system breaks down the carbohydrates from food into various sugar molecules - one of them is glucose, the body's principal source of energy. The glucose goes straight from the digestive system into the bloodstream after we have consumed and digested food. Glucose can only enter cells if there is insulin in the bloodstream too. Without any insulin the cells would starve.

After we eat, blood sugar concentrations rise, the pancreas releases insulin automatically so that the glucose enters cells, as more and more cells receive glucose, blood sugar levels come down to normal again. Excess glucose is stored as glycogen (stored glucose) in the liver and muscles.

After a meal blood glucose levels rise, insulin is released from the pancreas into the bloodstream, blood sugar levels fall back

If you have not eaten for a while and blood glucose concentrations keep dropping, the pancreas releases another hormone called glucagon. Glucagon triggers the breakdown of glycogen into glucose, thus pushing blood glucose levels back up to normal.
How do we measure blood glucose levels?
Blood sugar or blood glucose are shortened terms for blood sugar concentration or blood glucose level. Most mammals maintain their blood glucose levels at between 3.6 and 5.8 mM (mmol/l). The average human blood glucose level is approximately 90 mg/dl, which is equivalent to 5mM (mmol/l).

What are mmol/l and mM? - there are two ways of measuring blood sugar concentrations:

By molecular count, which is done in "moles"

- mmol/l stands for "millimoles/liter" (millimoles per liter). "mM" means the same as "mmol/l"
By weight, which is done in "grams"

- mg/dl stands for "milligrams/deciliter" (milligrams per deciliter)

The world standard unit for measuring blood sugar concentrations is mmol/l.
Our blood glucose levels fluctuate throughout the day
After each meal our blood glucose levels rise and then settle down after about an hour. They are at their lowest point before our first meal in the day, which for most people (not shift workers) is breakfast.

What is hyperglycemia

Persistently higher than normal blood sugar concentrations is known as hyperglycemia. People with poorly controlled diabetes, Cushing's syndrome and some other illnesses frequently suffer from hyperglycemia. It normally occurs when there is not enough insulin in the body, or the body is not responding to the insulin properly. Without insulin, glucose cannot get into cells, and just accumulates in the bloodstream.

The signs and symptoms of hyperglycemia are:
A dry mouth
Frequent urination (polyuria)
Increased thirst (polydipsia)
Suppressed appetite initially
Depending on the severity, there may also be fatigue, lightheadedness, blurred vision, headache and weakness

Long-term hyperglycemia may eventually lead to complications that affect the small blood vessels that supply the nerves, kidneys, retina and other organs. There is a risk of becoming blind, developing renal disease, erectile dysfunction, foot ulcers and other illnesses and conditions. It is possible to estimate a person's 10 year risk of retinopathy by measuring their blood glucose levels.

Slight blood glucose increase raises heart disease risk - researchers from Copenhagen University Hospital found that after checking data on 80,000 people, that even slightly elevated blood sugar concentrations can eventually lead to a 69% higher risk of ischemic cardiovascular disease. They added that the risk applies to both diabetics and non-diabetics.

One third of community hospital patients have high blood sugar concentrations - experts from Emory University in Atlanta, Georgia, USA, found that from 32% to 38% of all patients in community hospitals suffer from hyperglycemia. They added that people should have their blood glucose levels checked as soon as they are hospitalized, as this would most likely reduce the numbers of hospital complications in surgery and general medicine patients.

One study found that higher blood glucose levels can lead to cognitive decline.

What is hypoglycemia

This is when blood sugar concentrations fall below normal. Most people with hypoglycemia can tell by the symptoms associated with the condition (a significant minority cannot). Individuals with diabetes are not only susceptible to hyperglycemia, but hypoglycemia too.
The early signs and symptoms of hypoglycemia are:
Tingling lips
The hands, and other parts of the body start to tremble
The face goes pale (pallor)
Sweating
Pounding heart (palpitations)
Anxiety
Accelerated heart rate

The human brain is a voracious consumer of glucose, it neither manufactures nor stores glucose - the brain depends completely on glucose coming from the bloodstream.

Below are some symptoms linked to severe hypoglycemia:
Confusion and disorientation.
Drunken-like behavior
Concentration difficulties
A paranoid or aggressive mentality
Less commonly - seizures
Less commonly - the person loses consciousness
In severe cases there is a risk of death, almost exclusively among diabetes patients

Hypoglycemia may have several different causes, including:
Diabetes - when the patient takes too much insulin

Some medications - for example, quinine for the treatment of malaria.

Too much alcohol - if you drink too much without having eaten, your liver may not release glycogen.

Some illnesses - especially critical ones, such as severe hepatitis and disorders of the kidney. If the kidneys and liver do not work properly, it is harder for the body to break down and excrete medications. Anorexia commonly has hypoglycemia as one of its symptoms.

Excessive insulin production - certain illnesses may have insulinoma as one of its symptoms, for example, some tumors produce insulin-like chemicals; in some cases the tumor itself consumes so much glucose that there is not enough for the rest of the body. Gastric bypass surgery patients are more likely to suffer from hypoglycemia. Nesidioblastosis (beta cell enlargement) often results in the overproduction of insulin. Beta cells are the insulin-producing cells in the pancreas.

Disorders of the endocrine system - some pituitary and adrenal gland disorders may lead to abnormally low production and release of some hormones which play a key role in the production of glucose.

What is blood glucose monitoring?
Blood glucose monitoring refers to the regular testing of glycemia. Glycemia means how much glucose there is in the blood.

Blood glucose monitoring is an essential part of good diabetes control. Many have to check several times each day so that they can plan for activities, meals, and when to take their medications.

Typically, the diabetes patient tests blood glucose levels with a glucose meter - which comes with lancets (tiny needles), a logbook and test strips. There are several meter manufacturers which make a wide range of different devices - however, they all do the same, measure the patients' blood-glucose levels.

A Glucose Meter, test strips, lancet drum and lancing device (black)

How to use the glucose meter:
Set out the following in front of you - the glucose meter, a test strip, the lancet device, and an alcohol prep pad
Wash your hands with warm soapy water
Switch on the glucose meter and insert a test strip into it when the device is ready.
Wipe where you plan to prick your finger with an alcohol prep pad. Wait for the alcohol to evaporate
Prick your finger with the lancet and gently squeeze until you have a small drop of blood
Place the drop of blood on the strip (sometimes at the side)
Wait for the glucose meter to process the data
Read the result on the glucose meter screen. Depending on what the reading is, follow your doctor's instructions.
Keep a log of each glucose reading; this helps the doctors find the best treatment plan for you. With more modern devices, the reading results are automatically stored.

Regulatory authorities need to keep a close check on the accuracy of medical devices used for testing blood glucose levels. In 2009, the US FDA (Food and Drug Administration informed that blood glucose meters that used GDH-PQQ test strips could be giving false readings - and that that some patients might have been using too much insulin as a result.
In general, patients with diabetes type 2 test their blood sugar concentrations at least once each day. Those needing to take insulin, which includes everyone with diabetes type 1 and some with type 2, have to test their blood several times a day.

If you test your blood according to your doctor's instructions, you are more likely to achieve good diabetes control.

Written by Christian Nordqvist

View drug information on Glucagon.

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