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September 18, 2002


Question from Toronto, Canada:

My two year old son has diabetes, and I have frequently asked his diabetes team about the long term effects of low blood sugars. I have also seen many such questions asked here, and the answer is almost always that frequent severe lows may cause some impairment of cognitive skills later in life. How do you define a severe low? Is it defined by how one reacts or a blood glucose reading? What is the range of a blood glucose reading for a severe low? If possible, I would also like a similar definition for a moderate low. When it comes to frequency, how often is frequent?


There are different types of hypoglycemia such as:

Asymptomatic hypoglycemia: low blood sugar (frequently defined as less than 3mmol/L [55mg/dl] with no symptoms)
Moderate hypoglycemia: The body reacts with warning symptoms of hypoglycemia (autonomic symptoms).
Hypoglycemia unawareness: people experience symptoms from the brain (neuroglycopenic symptoms) without having had any autonomic warning symptoms beforehand. People observing can clearly see that there are symptoms.
Severe hypoglycemia: severe symptoms of hypoglycemia disable people temporarily, requiring the assistance of another person to give food or use a Glucagon Emergency Kit. Severe hypoglycemia may proceed to unconsciousness and convulsions.

As you can see there is no definite range of sugar values for lows other than the3mmol/L [55mg/dl] cutoff. By definition, hypoglycemia is any sugar level below this.

The most important thing is that the blood sugar levels there are symptoms functions similar to a thermostat (the glucostat) generally starting its symptomatology firing at 4 mmol/L [72 mg/dl]. Unfortunately, this glucostat is adjusted up or down much too easily. When the blood sugar level has been high for a couple of days there will be symptoms at a higher blood sugar level (pseudohypoglycemia), and when it has been low for several days, there will be symptoms at a lower sugar levels — less than 2.5 mmol/L [45 mg/dl].

Currently, intensified insulin regimens, insulin pumps included, which are aimed at the best metabolic control, have been found to be frequently associated with hypoglycemia unawareness, although an adequate education of people and their families and a little bit higher hemoglobin A1c target value have been able to sharply reduce this side effect of intensified therapies.