Glucose in Serum (Fasting)
This test measures the amount of glucose (sugar) in your blood after you’ve fasted for 8–12 hours. It helps assess how well your body uses sugar for energy and can indicate risk for diabetes or other metabolic conditions.
["A fasting blood sugar test helps check your blood sugar levels and identify potential diabetes or insulin resistance early."]
Key facts at a glance
- LOINC
- 107372-5
- Short code
- GPIbM Act/Nor PPP
- Synonyms
- GPIbM Act/Nor PPP
- Category
- glucose
- Sample
- plasma
- Container
- Lavender-top (EDTA) or Green-top (Heparin)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- turbidimetry
- 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 This Test Matters
Your doctor may order this test if you have symptoms like excessive thirst, frequent urination, unexplained weight changes, fatigue, or if you have a family history of diabetes. It’s also used during pregnancy (gestational diabetes screening) or before certain treatments.
What to Expect Before the Test
You’ll need to fast (not eat or drink anything except water) for 8–12 hours before the test. Your doctor will provide specific instructions. Bring any medications you’re currently taking, as some may affect results.
How the Test Works
A healthcare provider will draw blood from a vein in your arm. The sample is sent to a lab where glucose levels are measured using an enzymatic method. Results are compared to standard reference ranges to determine your blood sugar status.
What the Results Mean
Results are typically reported as a numerical value (e.g., mg/dL or mmol/L). Low or high values may signal conditions like hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar), respectively. Your doctor will interpret results in the context of your overall health.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Fasting Blood Sugar
Frequently asked questions
What does a high fasting blood sugar mean?
Can diet or lifestyle changes affect this test?
What if I have questions about my results?
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