Blood Sugar 101

​What Is a Normal Blood Sugar?

 

The term "blood sugar" refers to the concentration of glucose, a simple, sugar, that is found in a set volume of blood. In the U.S. it is measured in milligrams per deciliter, abbreviated as mg/dl. In most of the rest of the world it is measured in millimoles per liter, abbreviated as mmol/L.

 

The concentration of glucose in our blood changes continually throughout the day. It can even vary significantly from minute to minute. When you eat, it can rise dramatically. When you exercise it will often drop.

 

The blood sugar measures that doctors are most interested in is the A1c, discussed below. When you are given a routine blood test doctors usually order a fasting glucose test. The most informative blood sugar reading is the post-meal blood sugar measured one and two hours after eating. Doctors rarely test this important blood sugar measurement as it is time consuming and hence expensive. Rarely doctors will order a Oral Glucose Tolerance Test, which tests your response to a huge dose of pure glucose, which hits your blood stream within minutes and produces results quite different from the blood sugars you will experience after each meal.

 

Normal Fasting Blood Sugar

Fasting blood sugar is usually measured first thing in the morning before you have eaten any food. A truly normal fasting blood sugar (which is also the blood sugar a normal person will see if they have not eaten for a few hours) is:

 

Between 70 mg/dl (3.9 mmol/L) and 92 mg/dl (5.0 mmol/L) .

 

This is the finding of a considerable body of research. People whose blood sugar tests at this level do not develop diabetes over the next decade or longer. Those with supposedly normal blood sugars above 92 mg/dl often do. Nevertheless, most doctors consider any fasting blood sugar below 100 mg/dl (5.6 mmol/L) as completely normal

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Post-Meal Blood Sugar (Postprandial)

Independent of what they eat, the blood sugars of truly normal people are:

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Under 120 mg/dl (6.6 mmol/L) one or two hours after a meal.

 

Most normal people are under 100 mg/dl (5.5 mmol/L) two hours after eating.

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This is demonstrated by the graph at the top of this page, which shows the blood sugars measured during a study where normal people had their blood sugar sampled every few minutes after eating a high carbohydrate meal.

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What is an Abnormally Low Blood Sugar?

 

Blood sugars under 70 mg/dl (3.9 mmol/L) are considered to be hypoglycemic and should be avoided.

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If you are not on insulin or a drug that causes your pancreas to secrete insulin, a blood sugar 5 to 10 mg/dl slightly below this range, while it might be uncomfortable,is not dangerous unless there is evidence that it is continuing to drop. This is because home blood sugar meters often read lower than lab values, so a reading in that very slightly lower range might actually be normal.

 

However, if you are using insulin or a drug that causes your body to secrete insulin you must err on the side of caution and keep your blood sugar well over 70 mg/dl (3.9 mmol/L).

 

This is because home meters may also read higher than your actual blood sugar so your 70 mg/dl reading may actually be 62 mg/dl. Even more importantly, the insulin or oral drug that has lowered your blood sugar to this level may still be working to lower your blood sugar even more. So if you don't treat a reading near 70 mg/dl, it may go on to drop to a dangerously low level.

 

The dangerous levels of low blood sugar--the hypos that may require a visit to the ER--are those around 40 mg/dl (2.2 mmol/L) and lower. At those levels unconsciousness and brain damage can occur.

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Normal Blood Sugars in Pregnancy

Because the blood volume increases greatly during pregnancy, diluting blood sugar, normal blood sugar concentrations for pregnant women are lower than those for everyone else.

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Based on current research, normal pregnant women's blood sugar falls into this range:

 

Fasting:    70.9 ± 7.8 mg/dl

                 3.94 mmol/L ± .43

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One Hour Post Meal:    108.9 ± 12.9 mg/dl

                                        6.05 ± .72 mmol/L

 

Two Hours Post Meal:    99.3 ±10.2 mg/dl 

                                         5.52 ± .57 mmol/L 

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Pregnant women with diabetes should strive for these blood sugars:

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Fasting:                            79 mg/dl

                                         4.4 mmol/L

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One Hour After Meals: 122 mg/dl

                                        6.8 mmol/L

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Two Hours After Meals: 110 mg/dl

                                         6.1 mmol/L

 

You can learn about the studies that established these values HERE

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A1c Test Results

Unlike the previous blood sugar measurements, the A1c test does not actually measure of how much glucose is in your blood. Instead, what it measures is how much glucose has become permanently bonded to your red blood cells. From this it estimates how much glucose those red blood cells have been exposed to over the past several months.

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The A1c is reported as a percentage. This percentage reports what percent of your red blood cells have glucose bonded to them.

 

A truly normal A1c is between 4.6% and 5.4%

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Doctors like the A1c test because it is fast and because they believe it tells them how your blood sugar has been acting over a period of several months.

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The Calculator that Shows How Estimated Average Glucose is Supposed to Map to A1c

The calculator you will find HERE uses the formula doctors rely on to show you what average blood sugar is supposed to be connected with your A1c.

 

Unfortunately, the A1c test often gives a misleading result. This is prone to occur if you have anemia, abnormally long-lived red blood cells, or certain unusual red blood cell genes. The test assumes you have a normal number of red blood cells, so any condition that changes your concentration of red blood cells can produce a misleading A1c results.

 

An A1c of 5.1% maps to an average blood sugar of 100 mg/dl (5.6 mmol/L) or less when group statistics are analyzed, but normal variations in how our red blood cells work make the A1cs of truly normal individuals fall into a wider range. Some people's A1cs are always a bit higher than their measured blood sugars would predict. Some are always lower.

 

For many years the American Diabetes Association specifically stated that the A1c test should not be used for diagnosing diabetes. They recently changed their recommendations to allow the use of A1c for diagnosis, however the A1c often misses diabetes in people whose red blood cells are not entirely normal.

 

When in doubt about the accuracy of an A1c test result use a blood sugar meter and take a number of fasting and post meal blood sugar tests to determine if you are running blood sugars that are high enough to damage your organs.

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What A1c is Truly Good Enough for a Person with Diabetes?

Doctors have been taught that any A1c below 7.5% is "good control" for people with diabetes. However, this is true only if you define "good control" as meaning "Very likely to get neuropathy, retinal damage, and heart disease." Those of us who have had diabetes for decades have found that when we keep our post-meal blood sugars below 140 mg/dl most of the time we see A1cs that range from the 5.7% level down. This level appears to be good enough to avoid the classic diabetic complications.

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Heart attack risk rises in a straight line fashion as A1c rises from 4.6% but only becomes a significantly raised threat as A1cs go over 6%. You can learn more about the relationship of heart disease and blood sugar test results on this page: A1c and Post-Meal Blood Sugars Predict Heart Attack.

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The 1-Hour Glucose Tolerance Test Not the Fasting Glucose Testing Accurately Identifies Diabetes Risk

Many doctors still use the fasting glucose test to screen for diabetes and pre-diabetes as it is cheap and easy to administer. But research published in 2008 that was based on studying a group of 2,442 subjects who were free of type 2 diabetes at the beginning of the study found that fasting glucose tests were a very poor predictor of who in this group would develop diabetes.

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In contrast, the researchers found that the one hour reading on a glucose tolerance test did a good job of screening for people heading for diabetes. People whose one hour glucose tolerance test results were over 155 mg/dl and who had markers for metabolic syndrome--such as a concentration of fat around the belly and high blood pressure were those who were more accurately predicted to be likely to develop diabetes.

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Fasting Versus Postload Plasma Glucose Concentration and the Risk for Future Type 2 Diabetes Muhammad A. Abdul-Ghani et al. Diabetes Care 32:281-286, 2009 DOI: 10.2337/dc08-1264

 

The fasting glucose test often misses diabetes in the many people whose fasting blood sugars stay normal long after their post-meal blood sugars are rising into the range over 200 mg/dl (11.1 mmol/L) that even the conservative American Diabetes Association has identified as being where retinopathy and other serious diabetic complications begin to develop.

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More about the Study Whose Results Are Graphed Above

This research was conducted using a Continuous Glucose Monitoring System (CGMS) a device that uses a needle inserted into the abdomen to measure blood sugar every few minutes. It was presented at EASD, the major annual European diabetes conference in, September, 2006.  A screen shot from that presentation is found at the top of this page. 

 

It reported on the pattern of blood sugars of a group of normal subject, whose blood sugar was measured while they wore a continuous glucose monitor for an entire day. It was titled, "What is Normal Glucose? Continuous Glucose Monitoring Data from Healthy Subjects." Unfortunately, it doesn't appear to be available online any more. 

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The main findings presented in it were that, in normal people, the fasting blood glucose stays flat in the low 80 mg/dl (4.4 mmol/L) range throughout the night. After a high carb meal, normal people's blood sugar rises to about 125 mg/dl for a brief period, with the peak blood sugar being measured at 45 minutes after eating and then drops back under 100 mg/dl.

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This study also found that the same amount of carbohydrate eaten at a meal other than breakfast does not raise blood sugar anywhere near as high as it does at breakfast.

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A Second CGMS Study that Confirms this Range

A study of CGMS measurements taken in 74 normal people aged between 9 and 65 years old over a period of 3 to 7 days was published in June of 2010. It found the following:

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Sensor glucose concentrations were 71-120 mg/dl for 91% of the day. Sensor values were less than or equal to 60 or >140 mg/dl for only 0.2% and 0.4% of the day, respectively.

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Overall only 5.6% of sensor readings were were over 140 mg/dl. (7.7 mmol/L) and these higher readings were more frequent in people under 25 years old. Only 4.4% of the readings of those over 45 were over 120 mg/dl.

 

Only .4% of all readings were over 140 mg/dl. But most significantly, this group was screened to ensure they had all off the following: A1Cs less than 6.0%, fasting blood glucose 70 to 99 mg/dl, 2-h oral glucose tolerance test (OGTT) levels below 140 mg/dl and no antibodies characteristic of autoimmune diabetes. After all these tests, all 17 people over age 45 who met the screening criteria had NO CGMS readings over 140 mg/dl at all.

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This is probably because by the age of 45 people with the underlying genetic conditions that lead to diabetes, whose blood sugars would have been normal at younger ages, but who would have been getting higher than true normal readings after meals, would have progressed to where they failed the screening test. So it is a good bet that the people in the 45 and older age group in this study are truly, physiologically normal. With that in mind we are safe saying that normal people do not go over 140 mg/dl ever and are only rarely (4.4% of the time in this study) over 120 mg/dl--no matter what they eat.

 

Variation of Interstitial Glucose Measurements Assessed by Continuous Glucose Monitors in Healthy, Nondiabetic Individuals/ Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group. Diabetes Care June 2010 vol. 33 no. 6 1297-1299. doi: 10.2337/dc09-1971

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Why Does the Lab Sheet I Got With My Blood Test Give Much Higher "Normal" Values?

The reason that your doctor or lab might consider much higher numbers as "normal" is because doctors rely on "diagnostic criteria" set by the American Diabetes Association decades ago to define what are normal and abnormal blood sugar levels

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The science used to define these diagnostic levels is outdated and inaccurate. The ADA resists changing these diagnostic criteria for reasons that are almost entirely political. You can read the grim details of how these diagnostic levels were set and why they avoid diagnosing people with diabetes until they have already developed diabetic complications: HERE.

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The research described on the Research Connecting Organ Damage to Blood Sugar Level web page will make it very clear what blood sugar levels are normal and what levels are associated with the development of early diabetic complications.

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If your reason for wanting normal blood sugars is to avoid all diabetic complications and the blood sugar swings that make you hungry and exhausted, shoot for blood sugars that are truly normal. Not the ADA recommended levels that are high enough to damage your organs.

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Why Does My Doctor Think High Blood Sugar Levels are "Good Enough for A Diabetic?"

It takes work and study to bring diabetic and prediabetic blood sugars down to the normal, truly healthy levels. If you rely only on pills and do nothing else, the only blood sugar levels you will be able to get to are the much-too-high "good enough for a diabetic" levels which, as you can see elsewhere on this site, are "good enough" only if you think neuropathy, retinopathy and a heart attack are "good enough."

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Though your doctor may think you are too lazy to do the work needed to get normal blood sugars and may not bother explain to you what it takes to achieve normal numbers, people with diabetes CAN and DO attain these normal blood sugar numbers. You can, too. If you want some inspiration, check out this page: The 5% Club: They Normalized Their Blood Sugars and So Can You.

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Why Did My Doctor Tell Me It Is Dangerous to Lower A1C Below 6.5%?

Several years ago, The ACCORD Study found a slightly larger number of heart attacks among people who attempted to lower blood sugar using a cocktail of oral diabetic drugs. Another study of elderly patients treated at VA hospitals found that patients with longstanding diabetes whose blood sugar was lowered aggressively with outdated methods of dosing insulin did not improve their health outcomes. Influential doctors interpreted these studies to mean that lowering blood sugar to normal levels using any means was dangerous and family doctors have been brainwashed to believe this is true.

 

In fact, subsequent analyses of this data has revealed that in ACCORD the patients in the group that strove to lower blood sugar who experienced slightly more heart attacks were those in the "lowering" study group who failed to meet the lowered blood sugar targets. Those who succeeded in lowering their A1c did better than those who did not.

 

Further analysis linked the increase in heart attacks to the use of the now-discredited drug, Avandia, which raises the risk of heart attack independent of blood sugar level. Avandia was also given to all the participants in the veterans' study.

 

You can read more about these studies and see the published follow up studies that debunk the idea that lowering blood sugar increases heart attack risk HERE

 

There is not an iota of evidence that lowering blood sugar by cutting carbohydrates, using metformin, or by using a modern basal/bolus insulin regimen that does not cause severe hypos is dangerous. In fact, the data suggests that lowering blood sugar below 6.5% using safe methods reduces the incidence of all the classic diabetic complications.

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If your doctor tells you otherwise, he is showing that his "diabetes education" comes only from reading superficial one paragraph newsletter summaries of studies--which are notorious for ignoring the follow-ups to these studies which correct or point out their flaws.

 

Learn More About Normal--and Abnormal--Blood Sugars

If your blood sugar is anything but rock solid normal, it's time to learn a bit about the way that your body regulates blood sugar. Without an understanding of how normal blood sugar works, it is hard to understand what is going on in your body as control breaks down and even harder to fix it. This is discussed here: How Blood Sugar Control Works and How It Stops Working.

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If you want to understand your true risk of developing diabetes and what science has learned about process people go through as they develop diabetes, read: The Patterns in Which Diabetes Develops.

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What It Takes to Get Normal Blood Sugars

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Education

If you want to avoid diabetic complications, following doctors' orders is not enough. You must put in some time educating yourself about how your body works and what is in the food you eat. There is no pill or medication that will give you normal blood sugars without this effort.

 

Learn What Foods Your Body Can Handle

The simple technique you'll find here: How to Lower Your Blood Sugar has helped thousands of people regain their health, and it will work for you, too. Try this technique for a week and you'll end up with a much better idea of what foods make up an ideal "Diabetes Diet" for your own unique metabolism. You can print out a handy one-page flyer summarizing this technique and put it on your fridge to help motivate yourself.

 

Eliminate the Toxic Myths

It's time to stop blaming yourself for causing your diabetes. No matter what you read in the media or what your doctor tells you, diabetes is not caused by obesity. Believing that you caused your diabetes thanks to gluttony and sloth leads to self-hatred. Self-hatred leads to denial. Denial leads to amputation, blindness, and heart attack death. Free yourself of this Toxic myth by reading You Did Not Eat Your Way to Diabetes and learn what scientists have found are the real causes of Type 2 Diabetes.

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If you are feeling hopeless because you have failed at every other diet you've ever tried, the good news is that an effective diabetes diet is a lot easier and more forgiving than a weight loss diet. Learn why here: A Diabetes Diet is Different from and Easier than a Weight Loss Diet.

 

Exercise

Some people find exercise helps greatly with blood sugar control. Others find it has no impact. It has a lot to do with what has made you diabetic. If your problem is mostly insulin resistance, exercise is usually very helpful. If it is insulin insufficiency, exercise is beneficial but won't necessarily normalize blood sugars on its own.

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Meds

If you can't get to normal blood sugar levels by modifying what you eat and adding exercise, it's time to check out drugs that lower insulin resistance, most notably metformin.

The safest oral drugs for people with Type 2 are metformin and repaglinide and gliclazide (not available in the U.S.)

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Insulin

If oral drugs don't get the job done, its time for insulin. Today's ultra thin insulin needles don't hurt. Really. So if fear of needles has been keeping you from taking the next step, read this page: Insulin for Type 2 Diabetes and get up your courage. Unlike every other drug prescribed for diabetes, when used properly, insulin always works.

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Many doctors don't have the time to educate their patients about how to get insulin doses set at the levels that give the best control. So if you are on insulin and still getting poor control, it's time to hit the books. You'll find several helpful books in our resource page that can show you how to get insulin working properly. You will find them at The Best Books and Nutritional Software.

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That's it in a nutshell.

 

Now get out there and get NORMAL!