Our blood glucose levels, also called “blood sugar levels,” are key to our health.
You may already know that high or low blood sugar can cause minor problems like sweating or feeling angry. But they're also linked to many major health issues like stroke, coma, and even death. All because of glucose.
Monitoring our blood glucose levels helps prevent us from reaching these outcomes before it's too late. But what do normal blood glucose levels look like? What’s the best way to monitor them?
Let’s start by learning more about blood glucose itself.
Glucose (C6H12O6 if you’re ever on Jeopardy!) is a simple sugar, the most basic of all carbohydrates. It's the fuel that provides both plants and animals with the energy needed to survive.
Humans regulate blood sugar through hormones released from the pancreas. The average person has about one teaspoon of sugar in their bloodstream at any given time.
If our blood sugar goes too far above or too far below that one teaspoon, our pancreas releases hormones to keep the balance. The hormone insulin helps reduce blood sugar levels, while hormones like glucagon and cortisol can raise blood sugar.
There is no single magic number for blood sugar. Instead, there are many components of glucose to take into consideration.
The range of safe blood glucose levels differs from person to person. This change depends on external factors such as age, time of day, and our eating habits.
Different medical organizations and healthcare providers follow slightly different guidelines for acceptable blood sugar levels. Measured in milligrams of glucose per deciliter of blood (mg/dL), there are three main categories of acceptable blood sugar levels:
A medical “fast” is when we go more than eight hours without food and drink only water. (Think first thing in the morning after a quality night of shuteye.)
Fasting blood glucose levels are often taken in the morning just before breakfast. The American Diabetes Association (ADA) describes normal fasting blood glucose as anything under 100 mg/dL. The World Health Organization (WHO) provides a similar normal fasting range of 70-100 mg/dL.
This isn’t to say fasting blood glucose levels hovering near 100 mg/dL are great. Medical professionals recommend fasting blood glucose levels remain below 90 mg/dL.
An occasional reading near 100 is fine. But, studies published by the American Journal of Medicine show that those who consistently measure fasting blood glucose between 91-99 mg/dL are two times as likely to develop diabetes.
Additionally, the ADA recommends seeking your healthcare provider as soon as possible should two consecutive fasting blood tests reveal levels above 100 or below 70 mg/dL.
It’s also important to know how your body handles the sugars you eat as part of regular meals. And remember, it’s not just sugar and candy bars here. Glucose is a simple carbohydrate, so the carbs in our diet like bread, beer, and potatoes can spike blood glucose as well.
The scientific term (again, should you find yourself on a TV quiz show) for the post-meal test is a “postprandial glucose test” (PPG). The ADA says that for those without diabetes, a two-hour PPG test should show blood sugar levels between 70-140 mg/dL.
There’s a sweet spot here, as well. Medical data suggests PPGs taken two hours after eating should be under 100 mg/dL. If our post-meal glucose levels match pre-meal glucose levels, all the better. The further from that upper limit of 140 mg/dL, the healthier we will be.
Our blood glucose levels spike immediately after we eat. It makes sense — eating provides the energy our bodies will need for the next five to six hours. Healthy adults who test their blood glucose directly after eating should still return readings well below 200 mg/dL.
For the best health outcomes, the experts recommend our peak glucose levels after eating stay below 140 mg/dL. Keeping our blood sugar below this threshold helps keep us from the “prediabetic” range.
Some with prediabetes can experience common diabetic symptoms like fatigue and constant thirst. Others experience no symptoms at all. Keeping our max blood sugar below 140 mg/dL steers us clear of prediabetes and helps to prevent us from developing diabetes later on.
Regardless of mitigating factors like time of day or eating habits, any two tests taken two hours apart that show blood sugar over 200 mg/dL are cause for concern.
Those with consecutive blood sugar readings above 200 mg/dL should contact a medical professional immediately.
It can be difficult to remember this barrage of numbers. In the simplest terms, know that nondiabetic blood sugar levels between 70 and 140 mg/dL are generally considered normal.
Even should a nondiabetic’s blood sugar dip below that 70 mg/dL mark, it’s probably not a big deal. Nondiabetics often dip under that 70 mark without any ill effect.
For optimal outcomes, we want to aim for an average glucose of 105 mg/dL or less. And as with any health issue, if you’re uncertain, contact a medical professional.
Diabetes Mellitus (diabetes for short) is the group of disorders related to an abundance of glucose in the blood.
Type 1 diabetes is when the body cannot produce enough insulin. Type 2 diabetes is when the body cannot properly regulate and use blood glucose due to insulin resistance.
Those living with diabetes have slightly different “normal” blood sugar levels compared to nondiabetics. These ranges further change for pregnant women with gestational diabetes.
Additionally, individual factors such as age and medical history can also change what a physician would consider “normal” blood sugar for someone with diabetes.
As with any medical information, it’s critical to ask your doctor or healthcare professional.
Proper management of diabetes requires regular testing. For many diabetics, that means a fasting blood glucose test before breakfast.
The ADA recommends fasting blood sugar levels between 80 and 130 mg/dL for diabetics. Ideally, a diabetic in control of their condition can keep their fasting blood glucose around 110 mg/dL.
The science shows that keeping diabetic fasting blood glucose as close to or below 110 mg/dL improves overall health.
The two-hour PPG test is another benchmark for those managing diabetes. The ADA suggests two-hour PPG stay below 180 mg/dL.
Much like the blood sugar guidelines for nondiabetics, the ADA’s postprandial recommendation of 180 mg/dL should serve as the upper limit. For maintaining a healthy lifestyle, diabetics should aim for two-hour post-meal blood sugar levels at or below 140 mg/dL.
Diabetic or nondiabetic, our glucose levels usually peak around 30-60 minutes after eating.
For diabetics, a good target to aim for is blood sugar levels less than 80 mg/dL higher than a test taken right before the meal. The closer your post-meal and pre-meal blood sugar readings, the better.
Regardless, consider blood sugar readings over 240 mg/dL dangerous.
A1C is a type of hemoglobin, the oxygen-carrying substance in our blood. This reading is directly related to sugars.
Blood sugar levels rise and fall every day depending on many factors. A1C levels, on the other hand, change slowly over time. So, measuring A1C levels gives physicians a bigger-picture view of a diabetic’s overall health.
Most diabetics can expect an A1C test anywhere between twice and six times a year. Diabetics should aim for A1C levels below 7 percent.
A1C test results are sometimes labeled as “estimated average glucose” (eAG) tests. An A1C level of 7 percent correlates to an eAG of 154 mg/dL.
With all the talk of high blood sugar, it’s easy to forget that, for those with diabetes, low blood sugar is also a problem.
Taking too much insulin can result in hypoglycemia. For diabetics, blood sugar levels below 70 mg/dL classify as “hypoglycemic.”
Mild symptoms of hypoglycemia include:
For these mild symptoms, a glucose tablet or 1/2 cup of fruit juice will usually do the trick to return blood sugar levels to a safe range.
Should the problem persist, though, symptoms may get worse and include:
In the worst of cases, diabetic hypoglycemia can result in coma and death.
It’s important for diabetics to carry food that can raise their blood sugar should glucose levels fall below 70 mg/dL or if they notice symptoms of hypoglycemia.
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Okay. We have the data ranges for what we can consider normal blood sugar for diabetics and nondiabetics. Now we need the tools to take the measurements, right?
Past diabetics measured blood sugar levels using urine tests. Results came slowly and were often inaccurate.
Thankfully, advancing medical technology has created simple, accurate glucose meters for use in the privacy of our own homes.
Glucometers, also called blood glucose meters, are the most common method of checking blood sugar. Glucometers are small, simple computers that read glucose-sensitive testing strips.
Users prick a finger, collect a drop of blood onto the test strip, and insert the strip into the machine. Depending on the specific model, glucometers return blood sugar readings in less than a minute, and sometimes in as little as three seconds. They are available in most stores at affordable prices.
This isn’t to say glucometers are perfect. The most obvious drawback is the need to prick one’s fingers for every test. Many users find the finger pricks uncomfortable. That fear of pain is a big hurdle that scares many away from gathering blood glucose data.
In addition, those who rely on glucometers must constantly resupply their testing strips. Much like buying razors versus buying razor blades, test strips can get pricey.
While some glucometers come equipped with onboard memory, most do not. This forces users to keep blood sugar journals, writing down the time of each test and the corresponding blood sugar level.
Continuous Glucose Monitors (CGMs), on the other hand, are small wearable devices that can keep near-constant tabs on a person’s blood sugar.
Just like the glucometer offered a step up from old-style urine tests, CGMs, such as those offered by Nutrisense, offer the next level of glucose monitoring. A CGM adheres to the user’s skin. A small probe placed just under the skin takes readings as often as every five minutes.
In addition to their usefulness as a tool in lowering blood sugar, CGMs can offer many advantages over a traditional blood glucose meter:
Instead of pricking a finger for each and every reading, a CGM does not require any finger pricks except for an optional calibration.
Because a CGM can register a reading every five minutes, they can gather blood sugar data a glucometer can’t, like while a user is sleeping. Should blood sugar dip to dangerous levels while the user is sleeping, the wearer will know as soon as they wake up.
Continuous monitoring also gives more granular data about how diet and exercise affect blood sugar. And of course, more data = better data.
Older-styled glucometers have limited technology, but new CGMs come with real brains. A transmitter embedded in the device sends blood sugar data right to your smartphone.
That means instead of having to finger prick, insert a test strip and wait, CGM users simply open an app on their phones for their latest blood sugar readings. No more having to keep a blood sugar journal!
One difference to note between these technologies is the price. Where simple glucometers can cost anywhere from $9 to $60 on initial purchase depending on quality, getting set up with a new CGM can be $100 or more.
However, this standard glucometer price doesn't factor in the permanent cost of buying testing strips. Nor does it account for the cost of time and comfort paid to blood sugar journaling and finger pricks. Over the life of each device, it's easy to see how these prices more than even out in the long run.
Glucometers and CGMs don’t cover all the bases, though. While having personal data is key in the day-to-day management of diabetes complications, some tests still require a visit to the doctor.
The A1C hemoglobin test is a physician-ordered blood test. Because A1C levels aren’t as dependent on immediate external factors such as recent diet and exercise, these tests provide a bigger-picture look at how your body handles the maintenance of blood sugar. A1C tests are useful in seeing how dietary and lifestyle changes have affected blood glucose levels. Like all tests, A1C tests do have their pros and cons.
Fructosamine is a compound produced in the body when glucose combines with protein. Like A1C hemoglobin, measuring fructosamine levels provides another stable benchmark.
The difference is fructosamine tends to be a faster biomarker than A1C hemoglobin. For diagnosed diabetics, Fructosamine tests can show how diet and lifestyle changes affect blood sugar in as little as two weeks. A1C tests, on the other hand, measure changes over months.
And because fructosamine testing does not rely on hemoglobin, it can provide more accurate results for those with atypical blood cells. The only way to get these tests is by visiting your doctor.
The oral glucose tolerance test is a doctor-prescribed test that gauges how your body reacts to an influx of glucose. Any mother is probably groaning as they read this — oral glucose tolerance tests (aka “drinking the syrup”) are a standard test during pregnancy to check for gestational diabetes.
Pregnant or no, the test begins with a blood draw to determine a baseline blood sugar level. Then, the patient drinks eight ounces of liquid glucose, usually for a total of 75 grams of carbohydrates.
After a few hours, the test requires another blood draw to see how your body handles the influx of glucose. Results depending, the doctor may give a diagnosis or order more tests.
For the health-conscious or those worried about prediabetic symptoms, the idea of checking our blood sugar can seem daunting. It doesn’t need to be!
Blood sugar monitoring is, in all honesty, a relatively simple test that yields immediate, clear results. If only all our data came in such useful packets.