The Numbers Game: Understanding Your Blood Sugar Levels

So your blood sugar runs high- but what is considered ‘high’? Are they slightly elevated, or are they far above your target range? Are they improving with time or do they keep climbing? The first step to blood sugar control for people with diabetes is understanding your numbers, which can help you identify personal patterns and track your progress over time.  There are three main blood sugar measures to take into account: Fasting blood sugar, Post-prandial blood sugar, and Hemoglobin A1c.

Fasting blood sugar refers to the glucose level measured after several hours without food, like when you test first thing in the morning. At this point, your body has already utilized whatever carbohydrates you consumed the night before and is now running off of stored carbohydrates which means it is trying to be very efficient; you should have enough glucose in your blood to help your cells run but not much more than that. Any elevated levels are a sign that something is off and your body is not able to move glucose into your cells optimally. Whether this is due to a lack of insulin (generally type I diabetes or progressed type II) or because your cells are not as sensitive to the insulin as they should be (generally type II), a high fasting glucose at a physical exam is often a first warning sign of diabetes for patients.  A normal range is 70-100 mg/dL, with levels under 70 considered abnormally low and requiring intervention to bring them back up. Levels between 100 and 125 mg/dL fall within the prediabetic range, meaning you are at risk for diabetes and have some impairment of your glucose utilization, and levels over 125 mg/dL qualify as one sign of possible diabetes.

Post-prandial blood sugar simply translates to levels ‘after eating.’ This test is usually taken two hours after your last meal, and the numbers will generally be higher because you have just introduced a large volume of glucose into your system. Some degree of a blood sugar spike is normal after eating; your body digests whatever carbohydrate you consumed, breaks it down into small glucose molecules that enter your bloodstream, and insulin helps to move that glucose into the cells where it’s needed. Two hours after eating, a normal blood sugar level would return to under 140 mg/dL. For people with diabetes, that number is often over 180 mg/dL, which shows that your body is having a difficult time transporting the glucose from your blood stream into your cells. Your doctor may formally test this with an Oral Glucose Tolerance Test where you consume a controlled amount of glucose followed by blood testing two hours later, and levels over 200 mg/dL are considered within the diabetic range.

Hemoglobin A1c (often shortened to ‘A1c’) is a bit different than the other two tests because it reflects your average blood sugar over the last 90 days rather than at a set period of time. Your result is given as a percentage that shows how much residual glucose is stuck to your red blood cells, and a higher percentage means higher overall circulating levels of glucose. A normal A1c is under 5.7%, with the prediabetes range falling from 5.7% to 6.4%.  An A1c of 6.5% or higher is a major sign of possible diabetes as it shows that your blood sugar tends to run much higher than the desired range.

Once a person is diagnosed with diabetes, there are similar goals that indicate good control: Fasting blood glucose should be under 130 mg/dL; 2-hour postprandial levels should be under 180 mg/dL, and Hemoglobin A1c should be under 7%.

For your reference, here’s how all of these numbers compare to each other:

Fasting Glucose (mg/dL)

Postprandial Glucose (mg/dL)

Hemoglobin A1c

Normal levels

70 to under 100

Under 140

Under 5.7%

Prediabetes

100 to 125

140 to under 180

5.8% to 6.4%

Diabetes

126 or higher

180 or higher

6.5% or higher

Goal for people
with diabetes
(after diagnosis)

70-130*

Under 180

Under 7%

*Some doctors may prefer fasting blood sugars of 80 or over to minimize risk of hypoglycemia, which is often the case for elderly patients. All of these numbers can also be impacted by other medical factors including medications, chronic diseases, and inflammation, so the results alone may not constitute a diagnosis – always speak with your physician if you are concerned.

These ranges are also slightly different for pregnant women as they have a larger volume of blood and therefore will have automatically lower concentrations of glucose. Imagine diluting 4 ounces of iced tea with 4 ounces of water – it may taste be less sweet as it is less concentrated, but the entire glass will still have the same amount of sugar as the 4 ounces of iced tea alone, so the low concentration is somewhat deceitful. Instead, physicians generally test for gestational diabetes (the onset of new diabetes symptoms during pregnancy) with an Oral Glucose Tolerance Test where they test their blood sugar response to a concentrated high-glucose drink.

Nutrition is a major influencer of blood sugar control. The carbohydrates you consume correlate directly to your increase in blood sugar, though the magnitude of change is different for each individual. I’m familiar with the tendency of many patients to start medication and believe it negates any need for dietary intervention, but combining a carbohydrate-consistent diet with medications will optimize your results. There is solid research that diet modification can help to decrease your A1c while also helping you better understand how your food choices impact your blood sugars, and many endocrinologists routinely refer patients to dietitians for medical nutrition therapy.

For more information on understanding your numbers, check out these trustworthy websites:

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