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Diabetes and Your Brain

Low Blood Glucose Can Cause Sudden Trouble

If you tightly control your diabetes, it can be easier to accidentally slip into low blood sugar. And low blood sugar has more immediate, obvious effects on your brain than high blood sugar.

The symptoms of low blood sugar get worse the lower your blood sugar goes. It can affect your mood and make it difficult for you to think. You might get a headache, feel dizzy, have poor coordination, or have trouble walking or talking. Severely low blood sugar can give you seizures or convulsions, make you pass out, or put you in a coma.

Repeated bouts of low blood sugar can become problematic, says Gail Musen, PhD, assistant professor of psychiatry at Harvard Medical School in Boston.

“Going too low once in a while probably doesn’t have a huge long-term effect on the brain,” she says. But if you have frequent low blood sugar, you can become unaware of it, and it’s dangerous to live like that.”

This condition, called hypoglycemia unawareness, happens when your brain has trouble noticing  low blood sugar levels. When that happens, you won’t get the usual early symptoms of low blood sugar, such as nausea, hunger, shakiness, cold or clammy skin, or a pounding heart.

Usually these symptoms are enough to wake someone with diabetes up from sleep, but if you have hypoglycemia unawareness, you might not wake up, and your blood sugar can continue to drop until it’s an emergency.

Hypoglycemia unawareness can also catch you off-guard while you are driving and lead to an accident, or cause you to fall.

The jury is still out on whether repeated bouts of low blood sugar can cause long-term memory problems or raise the risk of dementia. One large study, called the Diabetes Control and Complications Trial, showed that low blood sugar does not have a long-term impact on memory or the ability to think in people with type 1. But another study suggests a link between a history of severe low blood sugar and a higher risk of dementia in older people who have type 2.

The bottom line is that careful diabetes control is important, Zonszein says. “Low blood glucose might not make you get dementia, but it feels terrible. High blood glucose may not feel terrible, but it might cause problems with dementia.”