What Is Normal Blood Sugar?

Lately I’ve been thinking about which carbohydrates might be added to the Ketogenic Mediterranean Diet to make it healthier yet remain diabetic-friendly.  Carbohydrates—some more than others—tend to elevate blood sugars in diabetics.  If I’m going to recommend adding carbs to the KMD, I have to give some idea what an acceptable blood sugar response would be.  An excessive rise in blood sugar level would necessitate eliminating that carbohydrate, reducing the serving size, or changing the diabetic medication regimen (increase a dose or add a new drug?) 

First off, I’ve reviewed what constitutes blood sugar levels in healthy non-diabetics before and after meals.  Those levels might give us some idea what to shoot for in diabetics. 

The following numbers refer to average blood sugar (glucose) levels in venous plasma, as measured in a lab.  Portable home glucose meters measure sugar in capillary whole blood.  Many, but not all, meters in 2010 are calibrated to compare directly to venous plasma levels.

Fasting blood sugar after a night of sleep and before breakfast: 85 mg/dl (4.72 mmol/l)

One hour after a meal: 110 mg/dl (6.11 mmol/l)

Two hours after a meal: 95 mg/dl (5.28 mmol/l)

Five hours after a meal: 85 (4.72 mmol/l)

(The aforementioned meal derives 50–55% of its energy from carbohydrate)

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Ranges of blood sugar for young healthy non-diabetic adults:

Fasting blood sugar: 70–90 mg/dl (3.89–5.00 mmol/l)

One hour after a typical meal: 90–125 mg/dl (5.00–6.94 mmol/l)

Two hours after a typical meal: 90–110 mg/dl (5.00–6.11 mmol/l)

Five hours after a typical meal: 70–90 mg/dl (3.89–5.00 mmol/l)

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Another way to consider normal blood sugar levels is to look at a blood test called hemoglobin A1c, which is an indicator of average blood sugar readings over the prior three months.  The average healthy non-diabetic adult hemoglobin A1c is 5% and translates into an average blood sugar of 100 mg/dl (5.56 mmol/l).  This will vary a bit from lab to lab.  Most healthy non-diabetics would be under 5.7%.

What Level of Blood Sugar Defines Diabetes and Prediabetes?  

According to the 2007 guidelines issued by the American Association of Clinical Endocrinologists:

Prediabetes (or impaired fasting glucose): fasting blood sugar 100–125 mg/dl (5.56–6.94 mmol/l)

Prediabetes (or impaired glucose tolerance): blood sugar 140–199 mg/dl (7.78–11.06 mmol/l) two hours after ingesting 75 grams of glucose

Diabetes: blood sugar 200 mg/dl (11.11 mmol/l) or greater two hours after ingesting 75 grams of glucose

Diabetes: random blood sugar 200 mg/dl (11.11 mmol/l) or greater, plus symptoms of diabetes

For my current thoughts on blood sugar goals for diabetics and prediabetics, please see the bottom half  of my “What is Normal Blood Sugar” page.

Steve Parker, M.D.