Symptoms of low blood sugar can start quickly. It may take just 10 to 15 minutes. If you have had diabetes for many years, you may not realize that your blood sugar is low until it drops very low.
If your blood sugar level drops below 70 (mild low blood sugar), you may feel tired, anxious, dizzy, weak, shaky, or sweaty. You may have a fast heartbeat or blurry vision.
If your blood sugar level continues to drop (usually below 40), your behavior may change. You may feel more irritable. You may find it hard to concentrate or talk. And you may feel unsteady when you stand or walk. You may become too weak or confused to eat something with sugar to raise your blood sugar level.