Blood sugar is a term often used when discussing metabolic conditions like diabetes. Although there are various ways to test blood sugar, many people are unsure what their ideal readings should be.
Understanding your ideal blood glucose levels can help you identify and manage hyperglycemia (high blood sugar) or hypoglycemia (low blood sugar) and keep you within your target range. It can also help to guide your diabetes treatment.
But what are normal blood sugar ranges?
In this article, you'll learn what blood glucose is, why the hormone insulin is so important for managing blood sugar, how diabetes plays a role, and what your ideal numbers should be.
What Is Blood Glucose?
Each of the macronutrients (fat, protein, and carbohydrates) serves a unique role in your body. In order for them to be used functionally, however, they must be broken down into their smallest units. For carbohydrates, the smallest unit is glucose
Once digested and broken down, glucose travels from your GI tract into your blood and is either picked up by your cells to be used as fuel, or it's stored as energy-in-waiting in fat cells.
Blood glucose, also referred to as blood sugar, is a measurement of the amount of glucose that's in your blood at any given time.
Why does blood sugar fluctuate?
The hormone insulin is responsible for shuttling glucose out of your blood and into cells where it can be used for fuel. Under normal conditions, your blood sugar increases after a meal, signaling insulin, which opens up the doors of your cells to allow glucose in.
This creates a typical post-meal fluctuation in blood sugar as it finds its way through your digestion, into circulation, and ultimately into your cells.
However, if the hormone insulin cannot do its job properly, issues can occur.
How Does Diabetes Affect Blood Glucose?
In diabetes, your insulin becomes unreliable at doing its job. In type 1 diabetes, your pancreas isn't able to make enough insulin, which can lead to disruptions in blood sugar as your cells have no way of picking up the glucose from your blood.
In type 2 diabetes, you may be making enough insulin, but your cells become resistant to its messages. In other words, insulin is knocking on the door to let glucose in, but your cells can't hear the knock.
In either case, glucose isn't able to follow its normal path from your digestive system, into circulation, and then into your cells.
What Should Your Blood Glucose Levels Be?
Even healthy people can have fluctuations in blood sugar throughout the day. Depending on what you ate, how much you ate, and even what time you ate, your blood sugar may spike or drop outside of its normal range.
So what should your blood glucose levels be?
Before we jump into the specifics, it's important to understand that everyone's body is different. For example, research shows that two healthy people can consume the exact same meal and have vastly different glucose responses.
Keep in mind that the way your body handles glucose will start with your digestion (how well you're breaking down carbs), and is impacted every step of the way from absorption into circulation, all the way to the moment your cells pick up (or don't pick up) the glucose in your blood.
With that being said, there are some general guidelines for healthy blood sugar levels. Below are three different measures that are commonly taken to assess blood glucose:
- Fasting blood glucose
- Postprandial blood glucose (post-meal)
- Hemoglobin A1C (HbA1c)
Fasting Blood Glucose
Even between meals, your blood will have some level of glucose in it. Your fasting blood glucose (FBG) measures how much glucose remains in your blood after a fast of at least eight hours. This test is typically taken in the morning after an overnight fast and before breakfast.
When you have high blood glucose levels after a fast, it indicates that your body is unable to clear glucose after ample time. Conversely, if your results show low blood glucose, it could mean that medications you're taking are lowering your blood sugar too much – but this is less common
Your blood sugar levels will indicate one of three categories: normal blood sugar levels, levels within the range of prediabetes, or levels that indicate diabetes. For FBG, the American Diabetes Association (ADA) recommends:
Normal: A fasting blood sugar level less than 100 mg/dL (5.6 mmol/L) is considered normal.
Prediabetes: If your fasting blood sugar level is from 100 to 125 mg/dL (5.6 to 6.9 mmol/L), it indicates that you have prediabetes.
Diabetes: If your fasting blood sugar is 126 mg/dL (7 mmol/L) or higher on two separate tests, it indicates diabetes.
In the prediabetes stage, your cells are becoming less sensitive to insulin, or you may not be producing enough. This is an excellent time to start making lifestyle changes through diet and physical activity.
Postprandial glucose, also known as your post-meal glucose levels, measures the amount of glucose in your blood following a meal. While it's normal for blood sugar to rise after you eat, measuring your post-meal glucose can give you an idea of how well your body is handling the glycemic load. If your post-meal glucose is high, it indicates that your cells aren't picking up glucose at a normal rate.
You can measure your postprandial glucose at home using a glucose meter.
Generally speaking, postprandial measurements should be taken one to two hours after your first bite of a meal. For example, if you sit down for lunch at 1:15 pm, take your glucose measurement somewhere between 2:15 and 3:15 pm.
With that being said, studies show that blood glucose peaks are typically observed no less than 90 minutes after your meal, with the ideal window for postprandial testing at one hour and 15 minutes after your first bite. Using the example above, that would mean checking your blood glucose at 2:30 pm.
Just like fasting blood sugar, postprandial glucose can also vary greatly depending on the individual. However, this measurement is particularly helpful for assessing complications of diabetes or risk factors that are associated with high blood sugar.
When your postprandial blood glucose is chronically high, it can cause a range of health problems, and not all of them are directly related to diabetes complications. For example, high post-meal blood sugar increases the risk of:
- Blood vessel damage
- Heart disease
- Immune dysfunction
- Issues with cognitive health
While other influences often accompany these health conditions, it does raise a red flag where blood sugar is concerned.
Normal postprandial blood glucose is 140 mg/dl when taken one to two hours after your last meal. If your blood sugar reads 200 mg/dl or higher, it indicates that you may have diabetes.
For people that currently have diabetes and are working to manage it, the normal postprandial level increases to 180 mg/dl.
Hemoglobin A1C (HbA1c)
While the fasting blood glucose and postprandial tests take moment-in-time measurements, the A1C test gives you information about your average blood sugar levels over the last three months.
Hemoglobin is a protein that's present in your red blood cells. When sugar enters your circulation, it attaches to hemoglobin, which is a normal and natural process. For people with high blood sugar levels, however, the amount of hemoglobin that has sugar attached will be much higher. Therefore, measuring your hemoglobin is one of the most accurate ways to get a big-picture view of what your blood sugar has been doing for the last few months.
This can be helpful in both diagnosing diabetes and prediabetes, as well as assessing how well your current diabetes care treatment plan is going.
HbA1c levels are broken down as follows:
Normal: A reading of 5.7% or below is a normal range
Prediabetes: Readings between 5.7% and 6.4% indicate prediabetes
Diabetes: A reading of 6.5 or above indicates diabetes
As mentioned, your personal blood sugar levels may vary from the "normal" ranges presented here, but this is a good guide to get you started. If you already have prediabetes or diabetes, then your healthcare provider can give you more information on your specific goals.
If you're concerned about your blood glucose, you can also request a blood sugar test like the HbA1c from your doctor or dietitian to see what's been happening over the last several months.
Generally speaking, healthy blood sugar levels will look like:
- Fasting blood sugar less than 100 mg/dL (5.6 mmol/L)
- Postprandial blood sugar 140 mg/dl when taken one to two hours after your last meal
- HbA1c at 5.7% or below
To learn more about healthy blood sugar, as well as how to monitor your blood sugar levels, reach out to BioCoach for expert guidance on your health journey.
- Zeevi, David, et al. "Personalized nutrition by prediction of glycemic responses." Cell 163.5 (2015): 1079-1094.
- Daenen, S., et al. "Peak-time determination of post-meal glucose excursions in insulin-treated diabetic patients." Diabetes & metabolism 36.2 (2010): 165-169.
- Collier, Bryan, et al. "Glucose control and the inflammatory response." Nutrition in Clinical Practice 23.1 (2008): 3-15.
- Blaak, E. E., et al. "Impact of postprandial glycaemia on health and prevention of disease." Obesity reviews 13.10 (2012): 923-984.
- Node, Koichi, and Teruo Inoue. "Postprandial hyperglycemia as an etiological factor in vascular failure." Cardiovascular Diabetology 8.1 (2009): 1-10.
- Sasso, Ferdinando C., et al. "Glucose metabolism and coronary heart disease in patients with normal glucose tolerance." Jama 291.15 (2004): 1857-1863.
- Astley, Christina M., et al. "Genetic evidence that carbohydrate-stimulated insulin secretion leads to obesity." Clinical chemistry 64.1 (2018): 192-200.