What’s a Normal Blood Sugar Reading for Your Age? See What Your Numbers Really Mean
Plus find out why waking up with high blood sugar may be a warning sign for diabetes
Keeping your blood sugar in check is important for everyone—not just those living with diabetes. Consistently-high glucose can lead to a variety of health issues in both the short- and long-term, so knowing your target numbers and tracking specific patterns is a necessity. But, how do you know your individual parameters, especially if you’ve just started self-monitoring? Here, our experts break down normal blood sugar by age to help you understand what’s considered average versus signs that you may benefit from a visit to your doctor.
What do blood sugar measurements mean?
First, let’s delve into what exactly a glucose reading is telling you. There are different ways to collect data here. The first is a blood glucose test, which measures the concentration of glucose (or sugar) in the blood, explains Rozalina Grubina McCoy, MD, Endocrinologist at University of Maryland Medical Center.
“As you imagine, blood sugar levels go up with eating and down with fasting and exercise or physical activity,” she says.
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A second way to measure is checking your hemoglobin A1C (or just “A1C”), she adds. This measures the percentage of your hemoglobin (a protein within red blood cells) that has glucose attached to it. A1C reflects the average blood sugar over three months or so, and represents cumulative exposure—both fasting and after eating, explains Dr. McCoy.
You can monitor your blood sugar through routine blood tests with your doctor, a glucose meter you use at home or with a wearable continuous glucose monitor (CGM).
What’s considered healthy, low or high blood sugar
“Normally, fasting blood sugars should be between 70 to 100 mg/dL, though lower values can still be normal if they occur naturally without taking a glucose-lowering medication,” says Dr. McCoy. “A fasting blood sugar above 125 mg/dL indicates diabetes, while a blood sugar between 100 to 125 mg/dL indicates prediabetes. Blood sugar is supposed to go up after eating, but should come back down to fasting levels within four hours.”
A healthy A1C level is 5.6 percent or less. A1C between 5.7 and 6.4 percent indicates prediabetes and 6.5 percent or higher is considered diabetic. (You can learn more about normal A1C levels by age here.)
“So, someone who has normal fasting blood sugar but higher A1C likely has a lot of blood sugar elevations after eating, suggesting that their health would improve most with changing their diet, for example,” offers Dr. McCoy.
The problem with high or low blood sugar
Why does this matter? The risk of diabetes complications goes up with higher blood sugar and A1C levels, particularly once A1C is above 8 or 9 percent, she explains.
Additionally, in the short term, blood sugar levels less than 54 mg/dL cause health problems because they’re too low, while blood sugar levels above 180 mg/dL start to cause problems because it is too high. With sugars above 180 mg/dL, people may have symptoms like frequent urination, dehydration, blurred vision, weakness and fatigue.
Normal blood sugar levels chart by age
Standard glucose is actually relatively consistent for adults when based on age alone. The real difference lies in the time of day and whether or not you have diabetes. Here’s a look at some of the important numbers according to a normal blood sugar by age chart from SingleCare. Generally, fasting refers to eight hours without consuming anything with calories (drinking plain water is allowed).
| Fasting | Before meals | 1-2 hours after eating | Bedtime | |
| Adults 20+ without diabetes | Less than 100 mg/dL | Less than 100 mg/dL | Less than 120 to 140 mg/dL | Less than 100 mg/dL |
| Adults 20+ with diabetes | Less than 100 mg/dL | 70 to 130 mg/dL | Less than 180 mg/dL | 100 to 140 mg/dL |
When high morning blood sugar may be a concern
One glucose reading you’ll want to pay special attention to is when you first wake up. There is something called the “dawn phenomenon,” where blood sugar rises naturally in the early morning because that is the time—based on our circadian rhythm—that our body makes stress hormones like cortisol to get us ready for the day, explains Dr. McCoy.
“So if you wear a continuous glucose monitor that tracks blood sugars continuously throughout the day, you would see that,” she says.
In type 2 diabetes, especially, there are two potential types of blood sugar patterns. In one, a person may wake up with higher blood sugar levels because the liver is constantly making sugar even when not eating, and this process can accelerate with type 2 diabetes. Then, levels improve during the day as people eat, the pancreas releases insulin in response to food and that glucose is utilized so that blood sugars go down, says Dr. McCoy.
Alternatively, people can wake up with moderate blood sugars because their liver isn’t overactive. But then they have insulin resistance, and so when they eat, their insulin that is released in response to food doesn’t work as well. That causes blood sugar to go up with eating, but it doesn’t come down to normal as fast as it should, she explains.
What’s a normal morning blood sugar reading?
For adults 50 and up, a normal morning glucose level is still around 70 to 99 mg/dL, 100 to 125 mg/dL is elevated and 126 mg/dL and above may indicate diabetes if confirmed on repeat testing, says Michael Snyder, MD, Obesity Specialist and Medical Advisor for FuturHealth.
“If you’re seeing consistently-high morning numbers, especially above 130 mg/dL, it’s a good idea to speak with your doctor,” he suggests. “A CGM can also help reveal patterns throughout the day and night to better understand what’s going on.” Just remember to share your results with your doctor to talk through the best course of treatment, lifestyle adjustments or medication to suit your specific needs.
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