Blood glucose is a sugar that the bloodstream carries to all cells in the body to supply energy. A person needs to keep blood sugar levels within a safe range to reduce the risk of diabetes and heart disease.
Blood glucose monitoring measures the amount of sugar that the blood is transporting during a single instant.
People obtain this sugar from the diet. The human body regulates blood glucose levels so that they remain moderate: Enough glucose to fuel the cells, but not enough to overload the bloodstream.
The blood's internal environment must remain stable to support vital bodily functions.
Blood glucose levels change throughout the day. After eating, levels rise and then settle after about an hour. They are at their lowest point before the first meal of the day.
In this article, we look at the ideal target levels for blood glucose, as well as providing an overview of glucose itself and how to keep blood sugar readings within healthy range.
Health authorities consider a normal fasting blood sugar level to be below 99 milligrams per deciliter (mg/dL).
In people with diabetes, the levels will change more. Instead of targeting a specific level, the aim of managing blood sugar is to keep the levels within a healthy range.
The American Diabetes Association recommend target levels of 70–130 mg/dL before eating for a person with diabetes. Within 2 hours of eating a meal, blood glucose levels should be less than 180mg/dL.
Glucose is a sugar that circulates the blood, serving as the body's main source of energy.
When a person takes in carbohydrates through the diet, the digestive system processes them into sugar molecules of different complexities. Complex carbohydrates, such as the lactose common in dairy products, are harder for the body to break down. They contain different types of sugar molecule.
Glucose is another product of carbohydrate breakdown. It is a simple sugar that cells in the body can easily convert to energy.
The sugar goes straight from the digestive system into the bloodstream after an individual consumes and digests food.
However, glucose can only enter cells if enough insulin is also circulating in the bloodstream. Insulin is a protein that makes cells ready to receive glucose. The cells would starve without enough insulin, or if they become too resistant to its effects.
After people eat, blood sugar concentrations increase. The pancreas releases insulin automatically to move glucose from the blood to the cells.
As more and more cells receive glucose, blood sugar levels return to normal.
The liver and muscles store excess glucose as glycogen. Glycogen plays an important role in achieving homeostasis, a balanced state in the body. It helps the body function during states of starvation.
If a person does not eat for a short period, blood glucose concentrations will fall. The pancreas releases another hormone called glucagon. Glucagon triggers the breakdown of glycogen into glucose, which pushes levels in the blood back up to normal.
Consistently high blood sugar levels are part of a condition called hyperglycemia.
People with poorly controlled diabetes, Cushing's syndrome, and some other illnesses often experience hyperglycemia. People taking oral steroids may also experience hyperglycemia while taking this medication.
Hyperglycemia normally develops when there is not enough insulin in the body, or when the cells become less sensitive to insulin.
Without insulin, glucose cannot enter cells, and it builds up in the bloodstream.
Common symptoms of hyperglycemia include:
- a dry mouth
- frequent urination
- increased thirst
A person might also experience:
Persistent hyperglycemia might also lead to insulin resistance, which reduces sensitivity to insulin and the amount of glucose that the cells absorb. This might eventually develop into type 2 diabetes.
The 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 from persistent hyperglycemia include:
- vision loss
- 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 extremely high or low blood glucose levels to cognitive decline.
Using neuron imaging, researchers showed that people who have diabetes and cognitive dysfunction also have reduced blood flow to the brain and a range of other anomalies that affect thought processes.
Hypoglycemia develops 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
- 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.
Some causes of hypoglycemia include:
- some medications, for example, quinine for the treatment of malaria
- taking too much insulin
- drinking alcohol without eating, as the liver may not release glycogen
- some illnesses, notably severe hepatitis and disorders of the kidney
If the kidneys and liver do not work correctly, breaking down and excreting medication from the body becomes harder.
Excessive insulin production or supplementation can lead to hypoglycemia. Some tumors can cause low blood sugar, as they produce chemicals similar to insulin. A tumor may also consume so much glucose that it does not leave enough for the rest of the body.
People who undergo gastric bypass surgery might also experience hypoglycemia, as they will be able to take in less food than they were able to before surgery.
Nesidioblastosis, a rare condition involving the enlargement of beta cells, often results in an overproduction of insulin. Beta cells produce insulin in the pancreas.
People with diabetes need to be especially careful to maintain steady blood glucose levels, but those without diabetes should also follow healthy lifestyle habits to avoid increasing the risk of developing the condition.
The glycemic index
The glycemic index can help people choose foods that will not disrupt their blood sugar levels.
The index gives a value to each food. Foods that will cause blood glucose levels to spike dramatically, such as candy, cakes, and junk food, are high in the glycemic index.
Those that will minimize fluctuations through a slow release of energy have a low score.
Measured against glucose, which is 100 in the index, Watermelon, for example, has a mean value of 76, honey is at 61, and chickpeas rank at 28.
The glycemic load (GL) is based on the GI. It provides a picture of the total impact a serving of food will have on energy levels.
What is blood glucose monitoring?
People use blood glucose monitoring to regularly test glucose levels in the blood.
It is an essential part of effective diabetes control. Many people with diabetes must check several times each day to plan for activities and meals, as well as scheduling doses of medication or insulin.
A person can test their blood glucose levels with a glucometer. They usually come with lancets, or tiny needles, a logbook to record results, and test strips.
How to use a glucose meter
Glucometers are easy to use. Take the following steps to successfully test blood glucose:
- 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 when the device is ready.
- With an alcohol prep pad, wipe the planned site of injection. Wait for the alcohol to evaporate.
- Prick the finger with the lancet, and gently squeeze the finger until a small drop of blood develops.
- Place the drop of blood on the strip.
- Wait for the glucose meter to process the data.
- Read the result on the screen of glucose meter.
- Follow your doctor's instructions in line with whichever reading shows on the screen.
- Keep a log of each glucose reading, as this helps the doctors find the best treatment plan. More modern devices allow automatic storage of data.
People with type 2 diabetes normally need to test blood sugar concentrations at least once each day.
Those who need to take insulin, which includes all people with type 1 diabetes and some with type 2, have to test their blood several times a day.
An accurate reading of the blood glucose level can help 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 at least 150 minutes of moderate-to-intense exercise each week 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 that a typical plate will be one-fourth meat, one-fourth starchy foods, and one-half non-starchy vegetables
Any person who experiences symptoms of low or high blood sugar should see a doctor, whether or not they have a diagnosis of diabetes.
People should aim for blood glucose levels that are below 99 mg/dL. Irregular or extreme blood sugar levels can lead to diabetes and other harmful complications.
Monitoring blood sugar at home is the best way to make sure levels stay within a healthy range.
Both hyperglycemia and hypoglycemia can lead to the more severe complications of diabetes, so eating mainly low-GI foods and exercising regularly can help keep blood glucose balanced.
Is low-sugar chocolate really better for my blood glucose?
Low-sugar chocolate may be two different things. One is chocolate sweetened with a sugar alternative, such as sugar alcohols. Examples include mannitol, xylitol, or isomalt.
While they are usually lower in sugar, they still have carbohydrates and can affect blood glucose. Also, they have a slight laxative effect. Chocolate sweetened with stevia may be a better choice for a low glycemic treat. Dark chocolate is better than milk chocolate, especially dark chocolate with a cocoa content of at least 70 percent.
Typically, dark chocolate has a reasonably low glycemic index of 42 and a glycemic load of 9. As with all dietary matters, moderation is key, so keep an eye on portion size and read nutrition labels.Deborah Weatherspoon, PhD, RN, CRNA Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.