Know Your Blood Parameter: FBS
- Summarised by TGHC Editorial Team
- May 25, 2025
- 3 min read
Updated: Dec 5, 2025
Parameter Name
Fasting Blood Glucose (FBS)
This parameter is a critical measure of the glucose level in the blood after an overnight fast, typically defined as not consuming any caloric food or drink for at least 8 hours prior to the test.
Test Type
Blood
The FBS test is performed on a blood sample, which can be drawn from a vein or via a fingerstick. This test is commonly used in both clinical and home settings to monitor glucose levels.
Normal Range
Normal: 70–99 mg/dL
Prediabetes: 100–125 mg/dL
Diabetes: ≥ 126 mg/dL
The normal range indicates healthy glucose metabolism, while values outside this range can suggest varying degrees of glucose intolerance or diabetes. Regular monitoring can help in early detection and management of these conditions.
High Levels Indicate
Prediabetes or diabetes. May also be temporarily elevated due to stress, illness, or medication.
High fasting blood glucose levels can reflect the body’s inability to properly utilize insulin, leading to elevated sugar levels in the bloodstream. This condition can be exacerbated by factors such as acute illness, hormonal changes, or certain medications that affect glucose metabolism.
Low Levels Indicate
Hypoglycemia, can occur due to excess insulin, fasting, or certain health conditions.
Low fasting blood glucose levels, or hypoglycemia, can result from various factors including prolonged fasting, excessive physical activity, or insulin overproduction. Symptoms of hypoglycemia can be acute and require immediate attention to restore normal glucose levels.
Why It's Tested
To screen for diabetes or hypoglycemia and monitor glucose control.
The FBS test is a fundamental tool in the diagnosis and management of diabetes, allowing healthcare providers to assess how well the body is regulating blood sugar levels over time. It is often used in conjunction with other tests to provide a comprehensive view of a patient's metabolic health.
Associated Symptoms (if abnormal)
High: Fatigue, thirst, frequent urination Low: Sweating, dizziness, confusion
Patients with abnormal fasting blood glucose levels may experience a range of symptoms. High levels can lead to excessive thirst, frequent urination, and fatigue, while low levels might cause symptoms such as sweating, dizziness, and confusion, which can be alarming and require prompt intervention.
What To Do If Abnormal
Recheck levels, consider HbA1c or OGTT. Modify diet, physical activity, and medications if needed.
In cases of abnormal fasting blood glucose results, it is essential to conduct further testing, such as the HbA1c test or an Oral Glucose Tolerance Test (OGTT), to confirm the diagnosis. Additionally, lifestyle modifications, including dietary changes and increased physical activity, may be recommended to help manage blood sugar levels effectively.
Common Conditions Related
Type 2 diabetes, insulin resistance, hypoglycemia
Fasting blood glucose levels are closely associated with several health conditions, most notably Type 2 diabetes and insulin resistance, which can lead to long-term complications if not managed properly. Hypoglycemia is another condition linked to abnormal glucose levels, requiring careful monitoring and management.
Nutrition or Lifestyle Connection
Balanced meals, fiber-rich diet, avoid skipping meals, manage stress and sleep.
Maintaining a balanced diet that includes fiber-rich foods, regular meals, and proper hydration is crucial for stabilizing blood glucose levels. Additionally, managing stress and ensuring adequate sleep are important lifestyle factors that can significantly impact overall metabolic health and glucose regulation.
References (APA Format)
Mayo Clinic. (2022). Fasting blood sugar test.
MedlinePlus. (2023). Blood glucose test.
American Diabetes Association. (2024). Diabetes guidelines.
