Anything too far outside the normal range of 70 to 120 in a blood glucose test is considered a dangerous blood sugar level.
Also known as hyperglycemia, high blood sugar levels are typically about 240 milligrams/deciliters. Any level above this can become dangerous.
Low blood sugar is known as hypoglycemia and is generally anything less than 70 milligrams/deciliters.
Oftentimes, hyperglycemia has no symptoms, but if they do occur, they are most commonly blurry vision, frequent urination, fatigue, persistent thirst and wounds that are slow to heal.
Most people with low blood sugar experience shaking, nausea and feeling unusually weak and drowsy. With severely low blood sugar, fainting and seizures can occur.
Blood sugar problems can be prevented by maintaining a healthy diet and getting an acceptable level of physical exercise.