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Diabetes-Related High and Low Blood Sugar Levels - Topic Overview

People who lose weight or develop kidney problems may not need as much insulin or other medicines as they did before they lost the weight or developed kidney problems. Their blood sugar may drop too low. Be sure to check your blood sugar often when your body goes through changes.

When your blood sugar level drops below 70 milligrams per deciliter (mg/dL), you will usually have symptoms of low blood sugar. This can develop quickly, in 10 to 15 minutes.

  • If your blood sugar level drops just slightly below your target range (mild low blood sugar), you may feel tired, anxious, weak, shaky, or sweaty, and you may have a rapid heart rate. If you eat something that contains sugar, these symptoms may last only a short time. If you have diabetes, you may not always notice symptoms of mild low blood sugar. This is called hypoglycemia unawareness. If your blood sugar is well controlled and does not change much during the day, you may have an increased risk for hypoglycemic unawareness.
  • If your blood sugar level continues to drop (usually below 40 mg/dL), your behavior may change, and you may feel more irritable. You may become too weak or confused to eat something with sugar to raise your blood sugar level. Anytime your blood sugar drops below 50 mg/dL, you should act whether you have symptoms or not.
  • If your blood sugar level drops very low (usually below 20 mg/dL), you may lose consciousness or have a seizure. If you have symptoms of severe low blood sugar, you need medical care immediately.

You may have symptoms of low blood sugar if your blood sugar drops from a high level to a lower level. For example, if your blood sugar level has been higher than 300 mg/dL for a week or so and the level drops suddenly to 100 mg/dL, you may have symptoms of low blood sugar even though your blood sugar is in the normal range. But if you have had diabetes for many years, you may not have symptoms of low blood sugar until your blood sugar level is very low.

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