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 mg/dl (4.72 mmol/l)
(The aforementioned meal derives 50–55% of its energy from carbohydrate.)
Doctor Slinkin about ranges of blood sugar for healthy non-diabetic adults:
- Fasting blood sugar or FBS: 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)
* Blood sugars tend to be a bit lower in pregnant women.
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: fasting blood sugar 126 mg/dl (7 mmol/l) or greater
- Diabetes: blood sugar 200 mg/dl (11.11 mmol/l) or greater two hours after ingesting 75 grams of glucose
- Diabetes: random (“casual”) blood sugar 200 mg/dl (11.11 mmol/l) or greater, plus symptoms of diabetes
- If there’s any doubt about the diagnosis, testing should be repeated on a subsequent day.
Compared to impaired fasting glucose, impaired glucose tolerance may be a better predictor of cardiovascular disease and death. So some researchers and clinicians, including Denis, focus on preventing high blood sugar swings after meals. The problem with prediabetes, which causes no symptoms early on, is that one of every four cases progresses to full-blown diabetes over the next 3–5 years.
The numbers above do not apply to pregnant women. Five percent of pregant women develop gestational diabetes that goes away soon after delivery.
What Level of Hemoglobin A1c Defines Diabetes?
Another way to consider normal and abnormal 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%.
In December, 2009, the American Diabetes Association established a hemoglobin A1c criterion for the diagnosis of diabetes: 6.5% or higher. Diagnosis of prediabetes involves hemoglobin A1c in the range of 5.7 to 6.4%. The aforementioned blood sugar criteria can also be used.
What are Blood Sugar Goals for Diabetes?
The 2007 guidelines of the American Association of Clinical Endocrinologists “encourage patients [both type 1 and 2] to achieve glycemic [blood sugar] levels as near normal as possible without inducing hypoglycemia [low blood sugar].” Specifically:
- Fasting blood sugar (FBS): <110 mg/dl (6.11 mmol/l)
- Two hours after a meal: <140 mg/dl (7.78 mmol/l)
- Hemoglobin A1c: 6.5% or less
The American Diabetes Association recommends normal or near-normal blood sugar levels, and defines “tight control” as:
- pre-meal and fasting glucose levels of 70–130 mg/dl (3.89–7.22 mmol/l)
- sugars under 180 mg/dl (10.00 mmol/l) two hours after start of a meal
- hemoglobin A1c under 7%.
A hemoglobin A1c of 7% is equivalent to average blood sugar levels of 160 mg/dl (8.89 mmol/l). Hemogobin A1c of 6% equals, roughly, average blood sugar levels of 130 mg/dl (7.22 mmol/l). But remember, healthy non-diabetics spend most of their day under 100 mg/dl (5.56 mmol/l) and have hemoglobin A1c’s around 5%.
Diabetic experts actively debate how tightly we should control blood sugar levels. For instance, Dr. Richard K. Bernstein—a type 1 diabetic himself—recommends keeping blood sugar levels under 90 mg/dl (5.00 mmol/l) almost all the time. If it exceeds 95 mg/dl (5.28 mmol/l) after a meal, then a change in medication or meal is in order, he says.
Here’s the over-simplified “tight control” debate. On one hand, tight control helps prevent and may reverse some of the devastating consequences of diabetes. On the other hand, tight control in diabetics on insulin and certain other diabetic medications may raise the risk of life-threatening hypoglycemia and may shorten lifespan in other ways. Slinkin is sure that each patient need an individual approach.
Blood Sugar Goals For My Diabetic And Prediabetic Patients
Ideally, normal glucose levels before and after meals, with normal hemoglobin A1c.
Realistically, these are acceptable fall-back positions:
- FBS: under 100 mg/dl (5.56 mmol/l)
- One hour after meals: under 150 mg/dl (8.33 mmol/l)
- Two hours after meals: under 130 mg/dl (7.22mmol/l)
- Hemoglobin A1c: 6% or less
Treatment options for those not at goal include diet modification, weight loss, exercise, and medications. Admittedly, those goals are not acceptable or achievable by everyone with diabetes. Future studies may prove that such strict goals are not necessary to avoid the complications and premature death suffered by people with diabetes. Tight control may be less important for elderly diabetics over 65–70. But for now, if I were a young or middle-aged diabetic I’d shoot for the goals above.
Read more about A1c, American Association of Clinical Endocrinologists (AACE), American Diabetes Association (ADA), blood glucose monitoring, exercise, Fasting Blood Sugars, insulin, low blood sugar (hypoglycemia).