Fasting Serum Glucose (Mass Concentration)
This test measures the amount of glucose (sugar) in your blood after you’ve fasted for at least 8 hours. It helps your doctor assess your blood sugar levels and check for conditions like diabetes or metabolic issues.
["A fasting blood sugar test helps diagnose or monitor blood sugar control."]
Key facts at a glance
- LOINC
- 35184-1
- Short code
- Glucose p fast SerPl-msCnc
- Synonyms
- Glucose p fast SerPl-msCnc
- Category
- glucose
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- 50 N/A – 400 N/A
- Fasting
- true
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84484
- SNOMED
- 302774002
- 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
Your doctor may order this test if you have symptoms of high blood sugar, such as excessive thirst, frequent urination, unexplained weight loss, or fatigue. It’s also used during routine check-ups for people at higher risk of diabetes or during pregnancy (gestational diabetes).
How It’s Done
You’ll need to fast (not eat or drink anything except water) for 8 to 12 hours before the test. A healthcare provider will draw blood from a vein in your arm. The blood sample is sent to a lab for analysis.
What to Expect
The blood draw usually takes a few minutes and may cause a slight pinch or discomfort. You can resume eating and drinking normally right after. If you have a phobia of needles, let your doctor know so they can provide additional support or alternatives.
Fasting Guidelines
Follow your doctor’s instructions carefully. Avoid caffeine, alcohol, or smoking before the test. If you’re pregnant, breastfeeding, or have a medical condition, discuss any special fasting rules with your provider.
Reference range
Adult: 10-40 U/LN/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.
High fasting blood sugar levels (above normal ranges) may indicate type 1 or type 2 diabetes, prediabetes, or other metabolic disorders. Low levels can signal hypoglycemia (low blood sugar), which may require medical attention. Regular monitoring helps manage chronic conditions and prevents complications like nerve damage or heart disease.
Short name
Fasting Blood Sugar
Frequently asked questions
How long does it take to get results?
What does a normal result mean?
Can I eat or drink anything before the 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