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Diabetes Health Center

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When Low Blood Sugar Has No Symptoms

WebMD Feature

No one with diabetes welcomes signs of low blood sugar, also known as hypoglycemia. Sweating and feeling shaky, dizzy, moody, and anxious are signs that your blood sugar is dropping. You know you must treat it quickly.

But what if your body stops giving you these warning signs? Not being able to feel low blood sugar is known as hypoglycemic unawareness. If you have it, you could pass out without ever knowing that your blood sugar has dropped.

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Read on to learn what makes it more likely and how to avoid it.

Who Gets Hypoglycemic Unawareness?

If you have diabetes, you can have low blood sugar -- whether you take insulin or other drugs to control it. It's most likely if you have type 1 diabetes. Once you have low blood sugar, it's harder for your body to respond to it in the future.

If you have type 1 diabetes, you're also more likely to stop feeling low blood sugar. But it can happen if you have type 2 diabetes, too. The longer you’ve had diabetes, the more common it is. The symptoms can start to fade after you've had diabetes for as little as 5 years. After 20 years, they may be too faint for you to notice. Or you may only have them after your blood sugar drops very low.

You're also more likely to have hypoglycemic unawareness if:

  • You have neuropathy, or damage to the parts of the nervous system that trigger your body’s response to low blood sugars.
  • You have strict blood sugar control and you are on an intensive insulin regimen (3 or more insulin shots a day), have a history of severe low blood sugar that requires aid from another person, or had recent low blood sugar.
  • You take drugs for your heart or high blood pressure that can mask your body's response to low blood sugar.

What Causes Hypoglycemic Unawareness?

When your blood sugar starts to drop too low, your body normally stops releasing insulin and starts releasing other hormones. These include glucagon and epinephrine. These hormones help keep your blood sugar stable.

Epinephrine is the same hormone that helps us during our “flight or fight” response. It causes the symptoms that people with diabetes usually feel when sugars start to drop. But if you keep having low blood sugars, your reaction to them will be blunted. If you don't feel the symptoms that signal low blood sugar, you may not know that your glucose levels are dropping. If your blood sugar levels get too low, you may pass out or have seizures and need emergency treatment.

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