There's a lot of interest in blood sugar these days, both in people with and without diabetes.
A blood sugar measurement reveals the concentration of sugar (or glucose) within your bloodstream. This sugar is absolutely vital — it is the primary source of energy for the brain, muscles, and other cells — but when there is too much of it, it leads to prediabetes and diabetes. Chronically elevated blood sugar levels can eventually raise the risk of dangerous long-term outcomes such as cardiovascular disease.
Monitoring blood sugar levels has always been a central part of diabetes management. Today, even people without diabetes are measuring their blood sugar as a way to monitor their metabolic health. But what’s considered a desirable blood sugar level can vary from one person to another. Your own blood sugar goals should be determined in consultation with your doctor, who will consider many factors, including your age, diabetes status, and the presence of any additional health conditions.
There’s more than one way to measure blood sugar levels. Different tests and biomarkers will speak to different aspects of your metabolic health.
If you’re testing yourself at home, you’ll generally have a choice between one of two devices for blood sugar measurement:
A glucose meter: This is a handheld device that measures your current blood sugar level. This device requires a drop of blood, which you will draw by pricking yourself with a lancet.
A continuous glucose monitor (CGM): This is a wearable device that monitors blood sugar levels around the clock, updating a smartphone app or dedicated receiver with new measurements as often as every 60 seconds. A CGM also records your blood sugar data and makes it easy to understand your short- and long-term glucose management trends.
In the United States, glucose meters and CGMs both report these glucose measurements in units of mg/dL (milligrams per deciliter). In other countries, mmol/L (millimoles per liter) may be more common.
In recent years, CGMs have become popular among people without diabetes or prediabetes who are hoping to use the technology to optimize their diet and exercise choices. There is little evidence, however, that people with normal blood sugar levels will benefit from monitoring their blood sugar levels so closely. The American Heart Association suggests that people with normal blood sugar levels test their blood sugar about once every three years.
Medical authorities such as the American Diabetes Association define “normal” blood sugar differently for different types of blood sugar measurements:
If you’re trying to interpret your own blood sugar results with home testing, it may be smart to take those results with a grain of salt. Aimée José, RN, CDCES, a diabetes coach based in the San Diego area, says that at-home glucose monitoring technology isn’t as accurate as a traditional blood draw at the lab. If you’re concerned about your own blood sugar results, speak to your healthcare provider.
A single measurement in the diabetic range is not enough to confirm a diagnosis of diabetes, unless it is accompanied by the symptoms of diabetes. Even then, your doctor may wish to run multiple tests to confirm the diagnosis.
Fasting Blood Sugar Levels
A fasting blood sugar measurement helps reveal your baseline blood sugar levels, without the influence of anything you’ve had to eat or drink recently. The easiest way to do a fasting blood sugar test is to take your measurement in the morning, before you’ve eaten anything for breakfast.
For some people with type 2 diabetes, a fasting blood sugar test is the most important measurement to regularly perform at home. The same test can be used to screen for prediabetes, diabetes, and gestational diabetes. People who use insulin will rely on a fasting blood sugar measurement to assess whether they are taking the right dosages of basal insulin.
After Eating/Random Blood Sugar Levels
As soon as you eat food, especially food that contains carbohydrates, your blood sugar concentration shoots up as your body converts the energy into glucose for your cells to use. To some extent, this blood sugar rise is healthy and normal, though people with diabetes generally experience increases that are both larger and longer-lasting.
Checking your blood sugar after a meal or another activity that can affect blood sugar levels (such as exercise) can be a valuable way of learning how your lifestyle choices are affecting your glucose metabolism. However, these blood sugar measurements can be trickier to interpret because they vary so much depending on the timing and composition of the food you’ve eaten recently, among many other factors. A CGM can help bring clarity by offering a much fuller view of the changes in your blood sugar from one minute to another.
At the doctor’s office, your clinician may take a random blood sugar test, or they may ask you to take a controlled version of this test, named a glucose tolerance test, in order to assess how well your body responds to sugar intake.
A1C Testing
An A1C test, also known as a hemoglobin A1C or HbA1C test, estimates your average blood sugar levels over the previous three months. This measurement offers you and your clinician the best overall look at your long-term blood sugar control.
The A1C test is a simple blood test that’s usually given in a doctor’s office. You don’t need to fast before taking this test, and the results are not significantly affected by what you’ve had to eat or drink in the hours before the test. You can also purchase at-home A1C tests, but they may be less accurate than a test given or ordered by your healthcare provider.
A1C measurements are used to help diagnose prediabetes and diabetes, and if you have diabetes already, the test is considered one of the gold standards for assessing how well your diabetes treatment is working. Most people who have diabetes will have their A1C tested at least twice a year. A CGM can also estimate your A1C level, a metric that is sometimes called a “glucose management indicator.”
Time in Range Measurements
Time in range, or TIR, is a new measurement reported by CGMs. This statistic shows how much of your day you spend within your target blood sugar range. TIR is mostly of interest to people with diabetes who use insulin, a powerful medicine that can cause hypoglycemia (low blood sugar) as a side effect. For most people with type 1 or type 2 diabetes, a TIR above 70 percent is recommended. That’s about 17 hours out of the 24 hours in a day.
If your blood sugar levels are in the prediabetic range, it can be difficult to know what it means for your long-term health.
“Prediabetes is the warning sign,” says Ben Tzeel, RD, CDCES, founder of Your Diabetes Insider. “It means your body is struggling to produce enough insulin and manage blood glucose levels on its own. It’s your opportunity to jump in and change the path you’re on, if possible.”
Many people with prediabetes go on to develop type 2 diabetes within five years. And even when it does not progress to type 2 diabetes, prediabetes is associated with an increased risk of cardiovascular, kidney, and liver diseases.
With positive lifestyle changes, however, it is possible to reverse the progression of diabetes and to move back into the normal blood sugar range. There are no drugs approved for the treatment of prediabetes, but some doctors prescribe metformin off-label. GLP-1 weight loss medications, which were originally developed to treat high blood sugar and type 2 diabetes, can also help drop the blood sugar levels of people who are overweight or have obesity back into the normal range.
If you have diabetes, your healthcare provider has probably already given you a blood sugar measurement — such as fasting blood sugar, A1C, or time in range — to target. Using diet, exercise, and medication to meet this target will help preserve your long-term health and reduce the risk of complications like cardiovascular disease, neuropathy, vision loss, and kidney disease.
The American Diabetes Association recommends glucose targets for most adults with diabetes who have glucose levels far above normal:
In some special cases, the recommended targets are even higher:
Children with diabetes may have higher glycemic targets, in recognition of how uniquely difficult it can be to manage the blood sugar of youngsters.
Older adults may have higher glycemic targets, due to hypoglycemia unawareness, other health conditions, and shorter life expectancy, among other factors.
It seems natural to wonder if it makes sense to set stricter blood sugar targets, for yourself or for a loved one, to lower the risk of complications as much as possible. Experts say, however, that it’s not usually possible to achieve perfectly normal blood sugar numbers if you have type 1 or 2 diabetes, and health authorities do not consider it realistic for the vast majority of patients.
“It isn’t fair, reasonable, or logical to expect people with diabetes to achieve perfect blood sugar targets every day,” José says. “There are too many variables beyond our control — particularly with type 1 diabetes — that we can only react to.”
In fact, bringing blood sugar levels too low can sometimes backfire. A landmark study of people with type 2 diabetes found that aggressively prescribing drugs such as insulin and sulfonylureas to lower blood sugar levels can actually increase the risk of harm. And in type 1 diabetes, lower blood sugar levels always carry a risk of severe hypoglycemia, an omnipresent and potentially dangerous side effect of insulin use.
Though a normal blood sugar level may be unrealistic or undesirable for many people with diabetes, there are still many healthy ways to lower blood sugar. Tzeel suggests starting with a new diet: “This is your chance to start eating fewer processed foods and choose more whole foods,” he says. A diet with fewer refined carbohydrates but plenty of fiber and protein can help reduce blood sugar spikes after meals.
Other lifestyle changes include increasing your physical activity, reducing stress, getting better sleep, and stopping smoking. If you have type 2 diabetes, weight loss can bring comprehensive metabolic benefits, including lower blood sugar levels. If you have type 1 diabetes and are overweight, weight loss can help fight insulin resistance that makes dosing insulin more challenging.
Some people with type 2 diabetes have been able to achieve diabetes remission by losing weight the old-fashioned way. And though remission is not possible with type 1 diabetes, a small number of people with the condition have achieved normal or near-normal blood sugar levels, without an undue risk of hypoglycemia, by making dramatic lifestyle changes.
These success stories are rare and shouldn’t be the model for most people with diabetes. “There is a big difference between what we hope people with diabetes can strive for in blood sugar management versus what is realistic to expect,” says Tzeel. But by collaborating with your healthcare team, you can settle on glucose management targets that are appropriate for you and will help you reduce the long-term risks of chronic high blood sugar.
There are several different ways to measure blood sugar levels, and doctors will often rely on more than one measurement to assess metabolic health and diagnose diabetes.
Most people without diabetes or prediabetes probably don’t need to monitor their blood sugar levels frequently.
While “normal” blood sugar levels may seem like an obvious goal for people with diabetes, they are not necessarily an appropriate target for everyone.
Healthy lifestyle changes like a more wholesome diet, increased physical activity, and better sleep habits can help lower your blood sugar in a safe and natural way.
