You Ask, We Answer: What Should My Normal Glucose Levels Be?

Shana Spindler PhD
Shana Spindler PhD
July 22, 2021

Have you ever measured your glucose levels and wondered: is this normal? Maybe you’re asking because your numbers spike after certain foods, and you want to know if that’s safe. Or maybe your glucose readings are low at night, and you’re curious if that happens to anyone else.

If you’ve searched the Internet and can’t find a simple explanation of normal glucose levels, you’re not alone. There isn’t an easy answer. In this article, you’ll learn why it’s important to collect personalized glucose data and what we know about nondiabetic glucose numbers.

The importance of knowing your glucose patterns

If you use a continuous glucose monitor (CGM), you’ll see that your glucose levels rise and fall throughout the day. Research is beginning to show that the human body doesn’t have a single normal graph for how glucose numbers will or should change over time. While one person’s glucose levels stay stable from morning to night, another person’s glucose readings swing from high to low, even when both people are exposed to similar foods and environments.

Without a standard graph to show what’s normal for everyone, what we can do is strive for optimal. Some researchers suggest that keeping glucose levels stable throughout the day is as important, if not more important, than lowering your average blood sugar levels. By learning about your own body’s reaction to food, exercise, and lifestyle habits, you can figure out your normal, and adjust your day-to-day choices to reach optimal glucose stability.

Post-meal glucose levels differ widely among people

The differences in blood sugar regulation between individuals is apparent in a 2015 Israeli study of 800 adult participants who used CGM for seven full days. The researchers found that post-meal glucose levels differed widely among study participants, even to the same standardized meal. For example, the researchers reported that a meal of bread (a food that is high in carbohydrates and expected to increase blood sugar levels) increased some participants’ glucose readings only slightly. But for other participants, bread caused a large increase in glucose levels. Their study highlights the large variability in glucose regulation after meals and offers evidence that some people might have opposite responses to the same food.

Why do two healthy, nondiabetic people respond so differently to the same food? The simple answer: we don’t know. It’s likely a complex combination of genetics, gut microbiome, and our environments. The only way to know your personalized glucose patterns is to collect the data—there isn’t a standardized meal plan that will provide stable glucose levels for everyone.

What we know about glucose levels in nondiabetic individuals

Much of the information online about normal blood glucose is targeted to prediabetic and diabetic individuals who must regulate their blood sugar into a standard range considered safe. According to the United States Centers for Disease Control and Prevention, the general recommendation for individuals with diabetes is that blood glucose readings before a meal should be between 80 to 130 mg/dL (4.4 to 7.2 mmol/L)and no higher than 180 mg/dL (10 mmol/L) two hours after starting a meal. But it’s very difficult to find information about the typical, real-life range of glucose levels for non-diabetic people.

With the increasing use of CGM in research using healthy participants, scientists are collecting data on day-to-day glucose levels in non-diabetic individuals. A 2019 study of 153 healthy, non-diabetic participants across the United States sheds some light on typical glucose values under real-life conditions. Keep in mind, while these numbers are from a healthy, non-diabetic population, they represent what is observed under real-life conditions, not necessarily what is optimal.

The researchers report the following real-life glucose readings:  

Average daytime glucose: 100 mg/dL (5.6 mmol/L) (plus or minus 7 mg/dL (0.4 mmol/L))

Average nighttime glucose: 98 mg/dL (5.4 mmol/L) (plus or minus 9 mg/dL (0.5 mmol/L))

Average 24-hour glucose for ages under 60 years old: 98-99 mg/dL (5.4-5.5 mmol/L)

Average 24-hour glucose for ages 60 years and older: 104 mg/dL (5.8 mmol/L)

We can quickly see that daytime glucose values are higher than nighttime glucose values and younger individuals have lower glucose readings than older individuals, on average. If you look at how much time participants spent in the range of 70 mg/dL (3.9 mmol/L) and 140 mg/dL (7.8 mmol/L), the median percent for day and night was 96% and 99% of the time, respectively.

How many people experience a lot of high or low glucose levels?

The authors of the 2019 study also report the frequency of glucose extremes, such as low glucose readings (hypoglycemia) and high glucose readings. In this study, the authors found that nearly 28% of participants experienced at least one hypoglycemic event (glucose levels below 54 mg/dL (3 mmol/L)). Only about a third of people spent much time (more than 30 minutes) with glucose levels less than 70 mg/dL (3.9 mmol/L), and about half of the participants spent 30 minutes or more above 140 mg/dL (7.8 mmol/L). Almost no one spent significant time below 54 mg/dL (3 mmol/L) or above 180 mg/dL (10 mmol/L), which indicates that normal glucose levels are typically kept within this range.

A strength of this study is that the authors excluded those with diabetes or obesity and anyone who was pregnant or taking medication that could affect glucose metabolism. However, 93% of the participants were white. Additional studies are needed to bolster these findings and address if these numbers remain consistent across races.

As you evaluate your glucose levels, remember that what is normal in the general population might not be what is optimal. For optimal health, the key appears to be stable blood sugar levels that aren’t too high. Remember, the only person who can reveal the diet and lifestyle modifications that will optimize your glucose regulation is you.

References

Glycemic Variability: How Do We Measure It and Why Is It Important?

Personalized Nutrition by Prediction of Glycemic Responses

Centers for Disease Control and Prevention: Manage Blood Sugar

Continuous Glucose Monitoring Profiles in Healthy Nondiabetic Participants: A Multicenter Prospective Study

Have you ever measured your glucose levels and wondered: is this normal? Maybe you’re asking because your numbers spike after certain foods, and you want to know if that’s safe. Or maybe your glucose readings are low at night, and you’re curious if that happens to anyone else.

If you’ve searched the Internet and can’t find a simple explanation of normal glucose levels, you’re not alone. There isn’t an easy answer. In this article, you’ll learn why it’s important to collect personalized glucose data and what we know about nondiabetic glucose numbers.

The importance of knowing your glucose patterns

If you use a continuous glucose monitor (CGM), you’ll see that your glucose levels rise and fall throughout the day. Research is beginning to show that the human body doesn’t have a single normal graph for how glucose numbers will or should change over time. While one person’s glucose levels stay stable from morning to night, another person’s glucose readings swing from high to low, even when both people are exposed to similar foods and environments.

Without a standard graph to show what’s normal for everyone, what we can do is strive for optimal. Some researchers suggest that keeping glucose levels stable throughout the day is as important, if not more important, than lowering your average blood sugar levels. By learning about your own body’s reaction to food, exercise, and lifestyle habits, you can figure out your normal, and adjust your day-to-day choices to reach optimal glucose stability.

Post-meal glucose levels differ widely among people

The differences in blood sugar regulation between individuals is apparent in a 2015 Israeli study of 800 adult participants who used CGM for seven full days. The researchers found that post-meal glucose levels differed widely among study participants, even to the same standardized meal. For example, the researchers reported that a meal of bread (a food that is high in carbohydrates and expected to increase blood sugar levels) increased some participants’ glucose readings only slightly. But for other participants, bread caused a large increase in glucose levels. Their study highlights the large variability in glucose regulation after meals and offers evidence that some people might have opposite responses to the same food.

Why do two healthy, nondiabetic people respond so differently to the same food? The simple answer: we don’t know. It’s likely a complex combination of genetics, gut microbiome, and our environments. The only way to know your personalized glucose patterns is to collect the data—there isn’t a standardized meal plan that will provide stable glucose levels for everyone.

What we know about glucose levels in nondiabetic individuals

Much of the information online about normal blood glucose is targeted to prediabetic and diabetic individuals who must regulate their blood sugar into a standard range considered safe. According to the United States Centers for Disease Control and Prevention, the general recommendation for individuals with diabetes is that blood glucose readings before a meal should be between 80 to 130 mg/dL (4.4 to 7.2 mmol/L)and no higher than 180 mg/dL (10 mmol/L) two hours after starting a meal. But it’s very difficult to find information about the typical, real-life range of glucose levels for non-diabetic people.

With the increasing use of CGM in research using healthy participants, scientists are collecting data on day-to-day glucose levels in non-diabetic individuals. A 2019 study of 153 healthy, non-diabetic participants across the United States sheds some light on typical glucose values under real-life conditions. Keep in mind, while these numbers are from a healthy, non-diabetic population, they represent what is observed under real-life conditions, not necessarily what is optimal.

The researchers report the following real-life glucose readings:  

Average daytime glucose: 100 mg/dL (5.6 mmol/L) (plus or minus 7 mg/dL (0.4 mmol/L))

Average nighttime glucose: 98 mg/dL (5.4 mmol/L) (plus or minus 9 mg/dL (0.5 mmol/L))

Average 24-hour glucose for ages under 60 years old: 98-99 mg/dL (5.4-5.5 mmol/L)

Average 24-hour glucose for ages 60 years and older: 104 mg/dL (5.8 mmol/L)

We can quickly see that daytime glucose values are higher than nighttime glucose values and younger individuals have lower glucose readings than older individuals, on average. If you look at how much time participants spent in the range of 70 mg/dL (3.9 mmol/L) and 140 mg/dL (7.8 mmol/L), the median percent for day and night was 96% and 99% of the time, respectively.

How many people experience a lot of high or low glucose levels?

The authors of the 2019 study also report the frequency of glucose extremes, such as low glucose readings (hypoglycemia) and high glucose readings. In this study, the authors found that nearly 28% of participants experienced at least one hypoglycemic event (glucose levels below 54 mg/dL (3 mmol/L)). Only about a third of people spent much time (more than 30 minutes) with glucose levels less than 70 mg/dL (3.9 mmol/L), and about half of the participants spent 30 minutes or more above 140 mg/dL (7.8 mmol/L). Almost no one spent significant time below 54 mg/dL (3 mmol/L) or above 180 mg/dL (10 mmol/L), which indicates that normal glucose levels are typically kept within this range.

A strength of this study is that the authors excluded those with diabetes or obesity and anyone who was pregnant or taking medication that could affect glucose metabolism. However, 93% of the participants were white. Additional studies are needed to bolster these findings and address if these numbers remain consistent across races.

As you evaluate your glucose levels, remember that what is normal in the general population might not be what is optimal. For optimal health, the key appears to be stable blood sugar levels that aren’t too high. Remember, the only person who can reveal the diet and lifestyle modifications that will optimize your glucose regulation is you.

References

Glycemic Variability: How Do We Measure It and Why Is It Important?

Personalized Nutrition by Prediction of Glycemic Responses

Centers for Disease Control and Prevention: Manage Blood Sugar

Continuous Glucose Monitoring Profiles in Healthy Nondiabetic Participants: A Multicenter Prospective Study