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The level of low blood of blood sugar at which symptoms occur will vary from one diabetic to another, so would be subjective. It is primarily affected by the general level of blood sugar control on a day-to-day basis, so may also change for the same patient over time. In someone whose usual daily blood sugar tends to be poorly controlled and is regularly running high, a sudden decrease of blood sugar into a range that would typically be considered normal may precipitate hypoglycemia symptoms. If the daily medicines of that patient is changed so that there is better daily control of the blood sugar and the body gets accustomed to that new level, then it will typically require a lower level of blood sugar to precipitate hypoglycemia symptoms.
For any given patient, we would prefer to stabilize the blood sugar control sot hat there are no symptomatic episodes of hypoglycemia, and the threshold needs to be adjusted to the level at which symptoms occur for that individual.
Regardless of the threshold at which symptoms occur, there is a concern with significant hypoglycemia. In this context, the threshold applies to all diabetics. Hypoglycemia is considered a blood sugar below 3.9 mmol/L and significant hypoglycemia would be considered a level below 2.8 mmol/L.
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