Blood sugar, or blood glucose, is sugar that the bloodstream carries to all the cells in the body to supply energy. Blood sugar or blood glucose measurements represent the amount of sugar being transported in the blood during one instant.
The sugar comes from the food we eat. The human body regulates blood glucose levels so that they are neither too high nor too low. The blood's internal environment must remain stable for the body to function. This balance is known as homeostasis.
The sugar in the blood is not the same as sucrose, the sugar in the sugar bowl. There are different kinds of sugar. Sugar in the blood is known as glucose.
Blood glucose levels change throughout the day. After eating, levels rise and then settle down after about an hour. They are at their lowest point before the first meal of the day, which is normally breakfast.
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How does sugar get into the body's cells?
The glycemic index shows how much sugar different foods provide.
When we eat carbohydrates, such as sugar, or sucrose, our body digests it into glucose, a simple sugar that can easily convert to energy.
The human digestive system breaks down carbohydrates from food into various sugar molecules.
One of these sugars is glucose, the body's main source of energy.
The glucose goes straight from the digestive system into the bloodstream after food is consumed and digested.
But glucose can only enter cells if there is insulin in the bloodstream too. Without 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 return to normal again.
Excess glucose is stored as glycogen, or stored glucose, in the liver and the muscles. Glycogen plays an important role in homeostasis, because it helps our body function during starvation states.
If a person does not eat for a while, blood glucose concentrations will fall. The pancreas releases another hormone called glucagon. Glucagon triggers the breakdown of glycogen into glucose, and this pushes blood glucose levels back up to normal.
High and low blood sugar levels
In healthy people, fasting blood sugar levels should be below 99 milligrams per deciliter (mg/dL).
In people with diabetes, the levels will fluctuate more, so the aim of managing blood sugar is to keep the levels within a healthy range.
The American Diabetes Association recommend target levels for a person with diabetes between 70 and 130 mg/dL before eating, and less than 180mg/dL 2 hours after eating.
The glycemic index
The glycemic index can help people to choose foods that will not upset their blood sugar levels.
The index gives a value to each food, so that people can know which ones to avoid.
Foods that will cause blood glucose levels to spike dramatically, such as candy, are high in the glycemic index. Those that will minimize fluctuations, because they release energy slowly, include are low. Measured against glucose, which is 100 in the index, Gatorade, for example, has a value of 89, honey is at 61, and chickpeas at 10.
The glycemic load (GL) is based on the GI. It gives an idea of the impact a serving of food will have on energy levels.
What is hyperglycemia
If blood sugar levels are always higher, this is known as hyperglycemia.
Some people need to take insulin because their body does not produce it.
People with poorly controlled diabetes, Cushing's syndrome and some other illnesses often experience hyperglycemia. People taking oral steroids may also experience hyperglycemia while they are on this medication.
Hyperglycemia normally happens when there is not enough insulin in the body, or when the body does not respond properly to the insulin.
Without insulin, glucose cannot get into cells, and so it accumulates in the bloodstream.
Signs and symptoms of hyperglycemia, or high blood sugar levels, are:
- A dry mouth
- Frequent urination
- Increased thirst
Long-term, complications of uncontrolled diabetes affect the small blood vessels that supply the nerves, kidneys, retina, and other organs.
Some serious problems that can develop include:
- Kidney disease leading to kidney failure
- Erectile dysfunction
- Foot ulcers
- Permanent nerve damage, causing numbness and tingling
- Poor wound healing
- Increased risk of heart attack or stroke
Research has also linked high blood glucose levels with cognitive decline.
What is hypoglycemia
Hypoglycemia happens when blood sugar concentrations fall below normal. People with diabetes have a higher risk of both hyperglycemia and hypoglycemia.
Early signs and symptoms of hypoglycemia are:
- Tingling lips
- Trembling in the hands, and other parts of the body
- Pale face
- Palpitations or increased heart rate
- Dizziness or lightheadedness
The human brain needs a constant supply of glucose. Severely low glucose can have the following effects:
- Confusion and disorientation
- Drunken-like behavior
- Difficulty concentrating
- A paranoid or aggressive mentality
- Less commonly, the person may experience seizures or lose consciousness
Among people with diabetes, severe hypoglycemia can be fatal.
The causes of hypoglycemia include:
- Some medications, for example, quinine for the treatment of malaria
- Drinking alcohol without eating, because the liver may not release glycogen
- Some illnesses, notably 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 can lead to hypoglycemia. Some tumors produce insulin-like chemicals, or a tumor may consume so much glucose that there is not enough for the rest of the body.
Gastric bypass surgery patients may experience hypoglycemia.
Nesidioblastosis, a condition involving beta-cell enlargement, often results in an overproduction of insulin. Beta cells are the insulin-producing cells in the pancreas.
Disorders of the endocrine system, such as some pituitary and adrenal gland disorders, may lead to abnormally low production and release of some hormones that play a key role in glucose production.
How can I maintain a healthy blood sugar level?
People with diabetes need to be especially careful to maintain steady blood glucose levels, but those without diabetes should also follow healthy habits to avoid putting themselves at risk.
What is blood glucose monitoring?
Blood glucose monitoring is the regular testing of glycemia, or glucose levels in the blood.
It is an essential part of good diabetes control. Many people with diabetes must check several times each day so that they can plan for activities and meals and know when to take their medications.
A person can test their blood glucose levels with a glucometer, which comes supplied with lancets, or tiny needles, a logbook, and test strips. A glucometer measures blood glucose levels.
How to use a glucose meter
It is fairly easy to use a glucometer.
People who take insulin need to measure their blood glucose levels frequently.
- Set out 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
- With an alcohol prep pad, wipe the place where you plan to prick your finger. Wait for the alcohol to evaporate
- Prick the finger with the lancet and gently squeeze until you have a small drop of blood
- Place the drop of blood on the strip
- 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, as this helps the doctors find the best treatment plan for you. With more modern devices, the reading results are automatically stored
Patients with type 2 diabetes normally test their blood sugar concentrations at least once each day. Those who need to take insulin, which includes everyone with diabetes type 1 and some with type 2, have to test their blood several times a day.
Getting an accurate reading of the blood glucose level can help to achieve good diabetes control.
Lifestyle choices can often help to control blood sugar. Eating a healthy diet with plenty of fruit and vegetables, maintaining a healthy weight, and getting regular exercise can help.
Other tips for controlling blood sugar include:
- Eating at regular times and not skipping meals
- Drinking water instead of juice and soda
- Choosing fruit instead of a candy bar
- Using portion control, so a plate will contain one fourth meat, one fourth starchy foods and one half non-starchy vegetables
Anyone who experiences symptoms of low or high blood sugar should see a doctor, whether or not they have been diagnosed with diabetes.