Glucose, Serum (Fasting)
This test measures your blood sugar level after you’ve fasted for 8–12 hours. It helps doctors check for diabetes, prediabetes, or other blood sugar issues.
["Fasting blood glucose helps assess your risk for diabetes and metabolic health."]
Key facts at a glance
- LOINC
- 1492-8
- Short code
- Glucose 1.5h p .5 g/kg Glc IV SerPl-mCnc
- Synonyms
- Glucose 1.5h p .5 g/kg Glc IV SerPl-mCnc
- Category
- glucose
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 70
- Ref high
- 100
- Critical range
- 50 N/A – 400 N/A
- Fasting
- true
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82947
- SNOMED
- 260395008
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why It’s Done
Doctors order this test to diagnose or monitor conditions like diabetes, high blood sugar, or metabolic disorders. It may also be used during pregnancy (e.g., gestational diabetes screening) or if you have symptoms like excessive thirst, fatigue, or frequent urination.
What to Expect
You’ll fast (no food or drink except water) for the required time before the test. A healthcare provider will draw blood from your arm. The sample is sent to a lab for analysis.
How It Works
The lab uses an enzymatic method to measure glucose in your serum. This test detects the amount of sugar circulating in your blood, reflecting how your body uses energy.
What the Results Mean
Results are compared to general reference ranges, but your doctor will interpret them in the context of your health history and symptoms. Abnormally high or low levels may signal underlying issues.
Reference range
Fasting: 70-100 mg/dLN/A
Fasting for 8-12 hours required. Water is permitted. Avoid chewing gum and smoking before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Glucose levels outside normal ranges can indicate diabetes (high levels), hypoglycemia (low levels), or other metabolic disorders. Chronic high glucose is linked to long-term complications like nerve damage or heart disease.
Short name
Fasting Blood Glucose
Frequently asked questions
What causes fasting blood glucose to be different from my usual results?
How often should I get this test?
Can I eat or drink anything before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy