Fasting Blood Glucose: What It Is and What Your Results Mean
Bottom line: Fasting glucose measures blood sugar after 8+ hours without eating. Normal is 70-99 mg/dL. It screens for prediabetes and diabetes.
What Is Fasting Blood Glucose?
Fasting blood glucose measures the amount of sugar (glucose) in your blood after you have not eaten for at least 8 hours. It is one of the most common blood tests used to screen for diabetes and prediabetes.
Glucose is your body's primary source of energy, derived from the carbohydrates you eat. Insulin, a hormone produced by the pancreas, helps move glucose from your blood into cells. When this system does not work properly, glucose accumulates in the bloodstream, leading to elevated fasting glucose levels.
This test is particularly important because prediabetes and early type 2 diabetes often have no symptoms. Catching elevated glucose early gives you the best chance of reversing it through lifestyle changes before it progresses to diabetes.
Fasting Blood Glucose Reference Ranges
| Classification | Range (mg/dL) |
|---|---|
| Severely Low (Hypoglycemia) | Below 55 |
| Low | 55 - 69 |
| Normal | 70 - 99 |
| Prediabetes | 100 - 125 |
| Diabetes Range | 126 - 400 |
What Affects Your Fasting Blood Glucose Levels?
- Diet, especially refined carbohydrates and sugar intake
- Physical activity level and exercise habits
- Body weight, particularly visceral fat around the abdomen
- Sleep quality and duration
- Stress levels and cortisol production
- Medications such as corticosteroids and some blood pressure drugs
When to Get Tested
The American Diabetes Association recommends fasting glucose screening starting at age 35, or earlier if you have risk factors such as being overweight, having a family history of diabetes, or a history of gestational diabetes. If results are normal, retest every 3 years. If in the prediabetes range, retest every 6-12 months.
Look Up Your Fasting Blood Glucose Result
Select your value below to see a detailed breakdown of what it means:
Severely Low (Hypoglycemia)
Low
Normal
Prediabetes
Diabetes Range
Read the Full Blood Sugar Guide
Frequently Asked Questions
A normal fasting glucose is 70-99 mg/dL according to the American Diabetes Association. Levels of 100-125 mg/dL indicate prediabetes, and 126 mg/dL or higher on two separate tests indicates diabetes.
Yes. The NIH Diabetes Prevention Program study showed that 150 minutes of weekly exercise combined with 5-7% body weight loss reduced diabetes risk by 58%. Diet changes like reducing refined carbs and increasing fiber also help significantly.
Black coffee may slightly raise blood sugar in some people, so it is best to drink only water during the fasting period before your blood test for the most accurate result.
