Fasting Blood Sugar (FBS)
Fasting blood sugar (FBS) refers to a blood glucose test that is performed after an overnight fast, typically for 8 to 12 hours. It is used to evaluate several aspects of glucose metabolism and is commonly employed for various purposes:
- Screening for diabetes: Fasting blood sugar is often used as a screening tool to assess for diabetes or prediabetes. Elevated blood sugar levels in the fasting state may indicate impaired glucose metabolism, which can be indicative of diabetes if persistent.
- Diagnosis of diabetes: According to the American Diabetes Association (ADA), a fasting blood sugar level of 126 milligrams per deciliter (mg/dL) (7.0 millimoles per liter [mmol/L]) or higher on two separate occasions is diagnostic of diabetes. However, a confirmatory test, such as an oral glucose tolerance test (OGTT) or glycated hemoglobin (HbA1c) test, is usually recommended for confirmation.
- Monitoring diabetes management: For individuals already diagnosed with diabetes, fasting blood sugar is commonly used to monitor blood sugar levels and assess the effectiveness of diabetes management strategies, including diet, exercise, medication, and insulin therapy. Consistently elevated fasting blood sugar levels may indicate inadequate diabetes control and may prompt adjustments to treatment regimens.
- Assessment of dawn phenomenon: Fasting blood sugar levels may help identify the presence of the dawn phenomenon, a natural rise in blood sugar levels that occurs in the early morning hours, typically between 2 a.m. and 8 a.m. in individuals with diabetes. Monitoring fasting blood sugar levels over consecutive days can help distinguish between dawn phenomenon and other causes of elevated fasting blood sugar.
- Assessment of fasting insulin resistance: Elevated fasting blood sugar levels may indicate insulin resistance, a condition in which cells fail to respond adequately to insulin, resulting in impaired glucose uptake. Insulin resistance is a key factor in the development of type 2 diabetes and metabolic syndrome.
- Risk assessment for cardiovascular disease: Elevated fasting blood sugar levels, even within the normal range, may be associated with an increased risk of cardiovascular disease. Fasting blood sugar testing can help identify individuals who may benefit from lifestyle modifications to reduce their risk.