Final answer:
Prediabetes is diagnosed when a person has a fasting blood glucose level between 100 and 125 mg/dL, indicating that their blood glucose is higher than normal but not yet in the diabetes range.
Step-by-step explanation:
Prediabetes is diagnosed when a person has a fasting blood glucose level that falls between 100 and 125 mg/dL. This means that if a person's fasting blood glucose level is below 100 mg/dL, it is considered normal. If it falls between 100 and 125 mg/dL, it is categorized as prediabetes. However, if the fasting blood glucose level is higher than 125 mg/dL, it indicates a diagnosis of diabetes.