Glucose measured in plasma after a 12-hour fast (plasma glucose)
This test checks your blood sugar level after you’ve gone without food for 12 hours. It helps doctors assess how well your body manages glucose, which is important for preventing complications like diabetes or metabolic disorders.
["A fasting plasma glucose test helps diagnose or monitor conditions related to blood sugar control."]
Key facts at a glance
- LOINC
- 1555-2
- Short code
- Glucose p 12h fast Ur-mCnc
- Synonyms
- Glucose p 12h fast Ur-mCnc
- Category
- glucose
- Sample
- urine
- Container
- Sterile urine container
- 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
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why is this test done?
Your healthcare provider may order this test if you have symptoms of high blood sugar (such as excessive thirst, frequent urination, or unexplained weight loss), a family history of diabetes, or if you’re at risk for metabolic issues. It’s also used during routine check-ups or to monitor existing conditions like diabetes.
How is the test performed?
You’ll need to fast (not eat or drink anything except water) for 12 hours before the test. A small blood sample is taken from a vein in your arm, usually by a phlebotomist. The blood is then sent to a lab for analysis.
What does the test result mean?
Results are interpreted based on clinical guidelines, but they help determine if your blood sugar is within a healthy range or if further action (such as lifestyle changes or medication) is needed. Your doctor will discuss the results with you in detail.
What can affect test results?
Factors like recent food intake, illness, stress, or certain medications can influence blood sugar levels. Skipping the fasting period or consuming food/drinks before the test will give inaccurate results.
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.
Clinical significance: This test is critical for diagnosing prediabetes, diabetes, or hypoglycemia. High levels may indicate insulin resistance or diabetes, while very low levels could signal underlying metabolic disorders or other health issues. Regular monitoring helps manage long-term risks.
Short name
Plasma fasting glucose
Frequently asked questions
How long does it take to get results?
Can I eat or drink anything before the test?
What should I do if I feel dizzy or weak 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