Low blood sugar (hypoglycemia) means that the level of sugar (glucose) in your blood has dropped below what your body needs to function normally. When your blood sugar level drops below 70 milligrams per deciliter (mg/dL), you will usually have symptoms of low blood sugar, which can develop quickly.

• If your blood sugar level drops just slightly below your target level (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 had diabetes for many years, 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 be at risk for hypoglycemia 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 to raise your blood sugar level.
• 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.

Check your blood sugar level often after you have taken steps to raise it to make sure your level returns to and remains normal. A low blood sugar level may soon recur, even though it has been treated. For example, the long-acting insulin can continue to reduce blood sugar levels for up to 36 hours after an episode of low blood sugar. Home blood sugar testing will help you identify a low blood sugar level.

If your episodes of low blood sugar levels are occurring more frequently, a visit to your doctor is needed.