If your blood sugar is getting too high or low, it can cause problems in different parts of your body. Too high blood sugar can lead to diabetes, a condition in which the level of sugar (glucose) in your blood is too high. High blood sugar can also damage nerve cells and other cells in the body. Low blood sugar can cause problems like dizziness, fatigue, and trouble concentrating. Monitoring your blood sugar helps you stay aware of how your diabetes is affecting your health.