Blood sugar levels are a key indicator of overall health—and it’s important to know the ideal range for your age group. While appropriate targets vary between individuals based on age, health conditions and lifestyle factors, understanding the typical ranges provides helpful insight into how your body is functioning.
Nonetheless, it’s crucial to note that the following information is provided only as a guideline. If you have any concerns about your blood sugar, it’s essential to speak with your medical provider for a comprehensive assessment. There’s no one “normal” blood sugar level—your target number depends on many personal health and lifestyle factors.
Below, learn more about blood sugar, including how it connects to your overall health, the range of normal levels and signs of abnormal blood sugar.
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What Is Blood Sugar?
Blood sugar, or glucose, is the primary type of sugar in the body. It comes from carbohydrates found in foods. Glucose is essential for providing energy to cells throughout the body, including brain cells.
Your blood sugar level fluctuates throughout the day as you eat, exercise and sleep. Stress and hormones also play a role. People with diabetes should monitor blood sugar levels closely to ensure they remain within the appropriate target range—often determined by a medical provider.
A blood sugar level outside the target range can have profound health implications. “When blood sugar levels are too high or too low, it can have serious health consequences, such as nerve damage, kidney damage and heart disease,” says Brenda Peralta, registered dietitian and certified diabetes educator at FeastGood.com.
High blood sugar (hyperglycemia) can lead to conditions like diabetes, cardiovascular disease and stroke, she explains. Low blood sugar (hypoglycemia) can cause confusion, anxiety, weakness, sweating and vision problems. Extremely low levels of blood sugar can result in seizures and fainting.
Why Does Blood Sugar Matter With Diabetes?
Diabetes is a condition that makes it difficult or impossible for the body to regulate glucose levels on its own. When someone is living with diabetes, their body is either unable to produce enough insulin—or make enough insulin available for use. Insulin is a hormone that helps the body use glucose for energy. When insulin levels are too low, glucose accumulates in the bloodstream and can damage organs and other tissues.
“Diabetes occurs when a person’s body cannot adequately manage sugar that’s ingested normally in our everyday diet,” says Jennifer Meller, M.D., chief medical officer at Sweetch—a digital health care innovation company based in Tel Aviv, Israel. “Chronically elevated sugar levels can lead to changes in both large and small blood vessels.”
Over time, changes to large vessels can lead to an increased risk of heart attack and stroke, while damage to small vessels can cause nerve damage, vision loss and kidney failure, explains Dr. Meller.
For people living with diabetes, maintaining healthy blood sugar levels is essential to preventing serious health complications in the future. This requires understanding target glucose levels for different age groups and making lifestyle changes accordingly, as blood sugar can go up or or down based on what you eat and when, among other factors.
What Is an A1c Number?
An A1c test, also called glycosylated hemoglobin, is a standard diagnostic tool used to measure a person’s average blood sugar levels over the past three months (90 days). It reflects how well your blood sugar is controlled during that time period.
“It’s an essential measure of blood sugar control in diabetes because it provides a long-term view of blood sugar levels and can help predict the risk of complications from diabetes,” explains Peralta.
The test uses a small blood sample to analyze the amount of hemoglobin—a protein found in red blood cells that carries oxygen and binds to glucose molecules. The higher the glucose level in your bloodstream, the more hemoglobin will bind to it and be detected by the A1C test. This test is often done with a finger prick in the doctor’s office..
An A1c number is expressed as a percentage, with higher percentages indicating higher levels of glucose in the bloodstream. A healthy A1c reading for someone without diabetes is between 4% and 5.7%. A value between 5.7% and 6.4% is considered prediabetic, while 6.5% and higher are consistent with diabetes.
One important note to consider about one’s A1c number is that it may be affected by other medical conditions such as anemia, which could result in an inaccurate reading. This is why looking at additional numbers, such as one’s fasting glucose, in conjunction with an A1c number, is usually recommended.
How Is Blood Sugar Tested?
Blood sugar is often tested with a glucometer, which measures the amount of glucose in a sample of blood. A small drop of blood from the fingertip or arm is placed on a test strip and inserted into the glucometer. The results display on the glucometer’s LCD screen within a few seconds.
Another way to test blood sugar is via continuous glucose monitoring (CGM), which typically involves placing a disposable, water-resistant sensor on the back of the arm or stomach. These sensors can be scanned with a reader, and can be used for three to 14 days, depending on the brand. Many CGM sensors are used along with a smartphone, allowing the individual and others (such as caregivers) the ability to see glucose trends over the last eight hours.
Those living with diabetes usually check their blood sugar levels several times a day, including before meals and snacks and two hours after eating.
In certain cases, a doctor may also order other tests, such as a fasting glucose test or an oral glucose tolerance test. These tests measure the glucose levels in the blood at specific times (fasting or after eating).