Allan ‘coach’ Bolton
A few months ago after hearing comments from a couple of high level diabetes experts my curiosity was aroused regarding a definitive blood glucose level that indicates clinical hypoglycaemia. So I went searching…
According to recent report the most accepted treatment alert value for hypoglycaemia is a blood glucose reading of 3.9mmol/L or less, if you’re in the US that’s 70 mg/dl or less (Seaquist et al., 2013). This is consistent with the Australian National evidence‐based clinical care guidelines for type 1 diabetes in children, adolescents and adults (Craig et al., 2011).
“If you’ve had type 1 for some time you might be thinking these numbers are higher than you agree with personally. For example, I’ve spoken to many people who have said things like, ‘I can function fine at BGLs below 3 mmol/L (50 mg/dl)’, I’ve probably said the same sometime in the past.
Respectfully, I’m afraid this is one of those cases where we tend to reinforce what we want to hear rather than what we need to hear.”
The task force report published by the American Diabetes Association and Endocrine Society found that a single BGL threshold value that defines hypoglycaemia in diabetes cannot be assigned because there are many blood glucose level thresholds that produce symptoms of hypoglycaemia.
For example, (among other responses) the onset of hypo symptoms can be blunted after antecedent, same day hypoglycaemia or exercise. This means, say a BGL of 3.9 mmol/L in the morning might produce hypo symptoms, yet later in the day after being hypoglycaemic in the morning it might take a BGL of 3.3 mmol/L or less to produce symptoms.
On the flip side, the opposite can occur where BGLs of say 5mmol/L can produce hypo symptoms in poorly controlled diabetes and where hypoglycemia is very infrequent.
Although 3.9 mmol/L is higher than the BGL threshold for hypo symptoms in both nondiabetic individuals and those with well controlled diabetes, it generally allows time to prevent clinical hypoglycemia previously defined as 3.5 mmol/L or less.
The hypo alert value of 3.9 mmol/L also provides some margin for the limited accuracy of monitoring devices at low-glucose levels. Yes, you heard me right, like any field assessment any blood glucose reading taken on any portable device is only ever an estimation. All devices have a margin of error. Given diabetes management is primarily driven by blood glucose levels the first thing I look for in the small print is the accuracy of the strips and meter combination I use, especially accuracy at lower blood glucose levels. Click here to view a summary table from a recent review (Freckmann et al., 2012) of blood glucose monitoring systems.
Basically, a BGL of 3.9 mmol/L tells you that clinical hypoglycaemia is likely coming your way and provides a opportunity for prevention rather than having to recover from hypoglycaemia.
Of course any treatment for a blood glucose reading of 3.9 mmol/L (70 mg/dl) needs to be considered in context relevant to preceding diabetes management, for example, insulin dose, timing of insulin, exercise and blood glucose trend - has it been rising or falling?
Although this alert value of 3.9 mmol/L (70 mg/dl) has been debated by many experts, the consensus is it can be used as a practical cut-off value in the classification of hypoglycaemia.
Craig ME, Twigg SM, Donaghue KC, Cheung NW, Cameron FJ, Conn J, Jenkins AJ, Silink M, for the Australian Type 1 Diabetes Guidelines Expert Advisory Group. National evidence‐based clinical care guidelines for type 1 diabetes in children, adolescents and adults, Australian Government Department of Health and Ageing, Canberra 2011.
Download PDF (3mb)
Freckmann, G., Schmid, C., Baumstark, A., Pleus, S., Link, M., & Haug, C. (2012). System accuracy evaluation of 43 blood glucose monitoring systems for self-monitoring of blood glucose according to DIN EN ISO 15197. Journal of diabetes science and technology, 6(5), 1060–1075.
Seaquist, E. R., Anderson, J., Childs, B., Cryer, P., Dagogo-Jack, S., Fish, L., Heller, S., Rodriquez, H., Rosenzweig, J. and Vigersky, R. (2013). Hypoglycemia and Diabetes: A Report of a Workgroup of the American Diabetes Association and The Endocrine Society. Diabetes Care.