Q: I have had type 1 diabetes for 40 years. Recently I’ve been noticing low blood sugar feelings (glazed, unable to concentrate) even when my blood sugar levels are normal or high. Sometimes I even have ketones when this happens. Is this what’s causing my symptoms?
A: Symptoms of low blood glucose (hypoglycemia) tend to change over time. Most people who have had diabetes as long as you have lose the early warning signs (shaking, sweating, rapid heartbeat) and only experience cognitive (mental) symptoms, such as the ones you described.
Interestingly, these types of symptoms can occur in different situations. Unusually high blood glucose, particularly when you don’t spend a lot of time in a high range, can temporarily impair mental function and lead to tiredness, confusion and mood changes. It is easy to confuse these with symptoms of hypoglycemia, so it is important to check your blood glucose whenever symptoms occur. You don’t want to start popping glucose tablets when your blood glucose is 300 mg/dl (16.7 mmol/l).
Another situation that can cause hypoglycemic symptoms is a rapid decline in blood glucose, such as falling from 300 (16.7) to 130 (7.2) within an hour. This may happen during intense exercise or when rapid-acting insulin is peaking. The rapid drop fools the brain into thinking that the blood glucose is low simply because it is coming down so fast.
Since you mentioned ketones in your question, it is worth noting that the presence of ketones, with or without elevated glucose levels, can indicate a lack of insulin in the body, a lack of dietary carbohydrates or an infection that is causing intense insulin resistance. Regardless of the cause, ketones reflect a conversion from carbohydrate to fat metabolism, which can also create some of the symptoms you described. The solution, as you can probably guess, is to make sure you’re taking enough insulin (and that the insulin you’re taking hasn’t spoiled), consume reasonable amounts of carbohydrate and see your physician to rule out an infection.
Want to learn more about hypoglycemia? Read “Understanding Hypoglycemia,” “Take a Bite Out of Hypoglycemia,” and “Exorcising the Specter of Overnight Hypoglycemia.”