Note: The normal range blood sugar levels are given below, highlighted in green, and are based mainly on those published by the American Diabetes Association. It should be noted that other health authorities and countries other than the United States may issue slightly different values but not sufficiently different in most cases to be of concern.
But first, the many factors involving blood tests and blood sugar levels are explained in more detail below.
A brief explanation about blood sugars
Human beings, and all other animals and other life forms, obtain sugar from the foods they eat. Sugar is an essential source of energy needed to support the metabolic activities performed by the body’s cells that keep us alive.
There are many types of sugar found in the foods we eat each day and all the sugars are carbohydrates, organic compounds comprised of molecules of carbon, hydrogen, and oxygen. You have probably heard of some of them, sugars such as sucrose, fructose, lactose, and so on. Those are among the more common sugars in the foods that, after being eating and passing through the process of digestion in the stomach, are converted to the simple form of sugar called glucose that is then delivered into the bloodstream.
So, when speaking of normal range blood sugars we really mean, more specifically, blood glucose. A normal range for blood glucose refers to the levels that normally occur in healthy human beings – as opposed to those individuals whose blood sugar levels are affected by sickness and poor health, especially the disease called diabetes. Diabetes is a serious disease in which the body’s normal process of regulating blood sugar levels to within a given safe range has become impaired.
Measuring blood sugars
Blood sugar levels can be measured by a self-administered test or by a clinical test that can be requisitioned by a physician.
Self administered with a Glucose Meter
Blood sugars can be measured with the aid of a simple glucose meter, a portable hand held device typically used by people with diabetes who must monitor their blood glucose levels fairly often. Although not measuring glucose in quite the same way as is done through a clinical blood test, glucose meters usually provide a sufficiently accurate measure of the blood glucose at the time the test is made.
Clinical blood test
The clinical blood test and analysis is more comprehensive, providing information on much more than current blood sugar levels and as such is an important diagnostic tool for doctors. Clinical blood tests are performed at the request of a physician. The blood test is a simple and painless procedure in which a trained technician draws a small sample of blood from a vein in the arm that is then sent for laboratory analysis. The same blood sample can also be used to measure many other factors in addition to blood glucose levels which is why it is a very useful tool for medical diagnosis. A clinical blood test is not normally taken very often, perhaps once per year or so, unless a doctor has reason to reconfirm a test or to more carefully check some particular health condition.
Units of measure
In the United States, blood sugar levels are measured using units of milligrams per decilitre (mg/dL) whereas in most other countries the units used are millimoles per liter (mmol/L)
An easy way to convert values to the U.S. system of mg/dL from the non-U.S. system of mmol/L is to multiply the mmol values by a factor of 18. For example 8.5 mmol/L would be equivalent to 153 mg/dL. (8.5 x 18). To convert the other way round, from mg/dL to mmol/L would be to divide the mg/dL values by 18, for example, 108 mg/dL equals 6 mmol/L (108 divided by 18)
Actually, sugar levels in the bloodstream fluctuate during the day, especially affected by the time since food has been consumed, the amount of energy expended in the course of the day’s activities, and by periods of rest and sleep.
The normal range blood sugar levels
For practical purposes of comparison, the blood sugar levels of an individual are usually determined by a blood test that is taken after either a period of 8 hours of not having eaten food, such as in the morning after a night’s sleep, called a fasting blood test, or at a time of 2 hours after eating a meal, called a post-prandial blood test. Not everyone rises at the same time in the morning or eats meals at the same time during the day of course.
For that reason, for practical purposes of comparison, it is customary to define the levels that would normally occur at times of the day related to the individual’s personal activities rather than at specific hourly times.
The first time of the day to test would be soon after not having eaten any food for a period of about 8 hours, referred to as a fasting level that would typically be in the morning after a night’s sleep.
A normal range blood glucose level is 70 to 99 mg/dL (3.9 to 5.5 mmol/L)
Post Prandial, 2 hours after a meal
Another important time to test to determine whether blood sugars are in the normal range is 2 hours after eating a regular meal.
A normal glucose level 2 hours after a meal is less than 140 mg/dL (<7.8 mmol/L)
The healthy body efficiently manages blood sugar levels and a test made “at random” more than 2 hours after a meal would normally provide a blood glucose range in the low to mid 100s, depending somewhat on the type of food eaten during a recent time period. For comparison, a person with diabetes might well have a blood-glucose content of 200 mg/dl or higher.
A normal range blood glucose level is about 70 to 125 mg/dL (4 to 7.0 mmol/L)
There are several other clinical tests that can be made, especially when diabetes or prediabetes is suspected.
The A1c (glycosylated hemoglobin) test
One of the most important of these is known as the Hemoglobin A1c, or A1c for short. And the test is sometimes referred to as the Glycosylated hemoglobin blood test. In simple terms, the A1c test provides a measurement, in terms of a percentage, of the number of hemoglobin molecules in the blood that have glucose attached to them.
A1c, glycosylated hemoglobin normal levels are less than 6% of total red blood cells
The A1c test is important because it determines the average blood sugar levels that have existed over a period of several weeks prior to the blood being taken. This is made possible because the millions of red blood cells produced by the body every second have an individual lifespan of approximately several weeks.
Abnormal blood sugar levels can occur
Temporary health conditions can cause temporarily abnormal levels of glucose in the blood. For that reason, if a blood test shows higher than normal glucose levels, a doctor would probably wish to have tests performed on more than one occasion in order to determine the real situation.
For more information on the diseases caused by blood sugars above the normal range, see Type-2 Diabetes and Prediabetes.