Glucose (Fasting)
A fasting glucose test measures blood sugar levels after an 8-12 hour fast, primarily used to screen for diabetes and prediabetes.
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Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
A fasting glucose test measures the concentration of glucose (blood sugar) after an individual has abstained from food and all beverages except water for at least 8 to 12 hours. Glucose is the body's primary fuel source, derived from the carbohydrates in foods like bread, fruit, pasta, and rice, which are broken down into glucose during digestion. The hormone insulin, produced by the pancreas, enables cells to take up glucose from the bloodstream and use it for energy.
By measuring glucose in a fasted state, the test captures the body's baseline ability to regulate blood sugar without the influence of a recent meal. This makes it a practical first-line tool for screening for diabetes and prediabetes, evaluating hypoglycemia (abnormally low blood sugar), and monitoring metabolic health over time. Abnormal fasting glucose levels may indicate that insulin production or insulin sensitivity is not functioning as expected, prompting further investigation with tests like A1c or fasting insulin.
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals over age 35 who want routine diabetes screening as part of preventive healthcare
- Those with family history of diabetes or prediabetes who may have increased genetic risk
- People experiencing symptoms such as excessive thirst, frequent urination, fatigue, blurred vision, or unexplained weight loss
- Individuals with risk factors including overweight or obesity, sedentary lifestyle, or high blood pressure
- Those with previous glucose test results that were borderline or elevated
- People with conditions that may affect blood sugar, such as metabolic syndrome or insulin resistance
What to expect
Preparation
Individuals should not eat or drink anything except water for 8 to 12 hours before the test. Many doctors prefer to have this fasting glucose test done in the morning before breakfast. It's important to maintain normal activities and medication schedules unless specifically instructed otherwise by a healthcare provider. Individuals should inform their provider about any medications they're taking, as some medications can affect glucose levels.
Sample Type
A small blood sample is collected through a routine blood draw from a vein, typically in the arm.
Collection
Blood is drawn from a vein, usually from the inside of the elbow or back of the hand, using a needle inserted into the vein, and blood is collected in an air-tight vial. Some people may feel moderate pain when the needle is inserted, while others feel only a prick or stinging sensation, with possible mild throbbing or bruising afterward. The collection process typically takes just a few minutes and no doctor visit is required.
Turnaround
Laboratory fasting blood sugar test results are usually available within hours or days. Most patients receive their results within 1-2 business days through their online patient portal or by phone.
Understanding your results
Normal fasting glucose levels fall between 70 and 99 mg/dL. Results above this range may indicate impaired fasting glucose (prediabetes) or diabetes, while levels below 70 mg/dL may suggest hypoglycemia. Laboratory blood draws from a vein are considered more accurate than fingerstick glucose meters or continuous glucose monitors. Healthcare providers interpret fasting glucose alongside symptoms, medical history, and complementary tests (such as A1c and insulin) to build a complete picture of metabolic function.
| Population | Reference Range | Notes |
|---|---|---|
| Adults (General) | 70-99 mg/dL | Normal fasting glucose levels for healthy adults without diabetes |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
A fasting blood sugar of less than 70 mg/dL is considered low blood sugar for someone with diabetes, but may be normal for someone without diabetes. Decreased glucose levels may result from endogenous or exogenous insulin excess, prolonged starvation, or liver disease. For some people, mainly those who are thin and young, a fasting blood sugar level below 70 mg/dL may be normal. Low glucose levels may cause symptoms like shakiness, and healthcare providers may recommend additional testing to determine if this represents a pattern.
What does a “High” result mean?
Fasting blood sugar levels of 100 to 125 mg/dL typically indicate prediabetes, meaning blood sugar levels are higher than normal but not high enough to be classified as diabetes. Levels of 126 mg/dL or above on more than one testing occasion usually indicate diabetes. Elevated glucose levels may also occur with pancreatic neoplasms, hyperthyroidism, and adrenocortical dysfunction. High glucose levels require medical evaluation to determine the underlying cause and appropriate treatment approach.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. At LevelPanel, protecting patient privacy is a fundamental commitment that extends far beyond basic compliance requirements. When individuals choose to order a glucose test through our platform, they can be confident that their results remain completely confidential and are <u>not reported to their personal doctor</u> unless they specifically choose to share them. Unlike tests ordered through traditional healthcare settings, these results are <u>not added to medical records</u> maintained by healthcare providers or insurance companies, giving patients complete control over their health information. The confidential nature of direct-to-consumer testing means that glucose results will <u>not appear on insurance explanation of benefits statements</u>, protecting individuals from potential concerns about insurance implications or unwanted questions from family members who may see insurance documents. Results are never shared with employers, government agencies, or third-party organizations without explicit patient consent. This privacy protection is particularly valuable for individuals who want to monitor their glucose levels proactively, check their diabetes risk, or verify results from other testing without creating a permanent record in their official medical file. The secure online portal ensures that only the patient can access their results using personalized login credentials.
Frequently asked questions
Related tests
Hemoglobin A1C
Provides a 2-3 month average of blood glucose levels, complementing the single-point-in-time measurement from fasting glucose
View TestComprehensive Metabolic Panel
Includes glucose measurement along with other metabolic markers like kidney function and electrolytes for broader health assessment
View TestInsulin Test
Measures insulin levels to help evaluate insulin production and effectiveness, particularly useful when glucose levels are abnormal
View TestRelated conditions
Related articles
Should I Get Tested for Diabetes? A Simple Decision Guide
Read ArticleYour A1C Is 5.7. What Does Prediabetes Actually Mean?
Read ArticleBlood Sugar Optimization: Going Beyond Normal
Read ArticleHow Fasting Affects Your Blood Test Results
Read ArticleLast reviewed: April 2026
CPT Code: 82947
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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