Glucose in plasma (fasting)
This test measures the amount of glucose (sugar) in your blood after you’ve fasted for a set period. It helps assess your blood sugar levels and overall risk for diabetes or other metabolic conditions.
["A fasting plasma glucose test checks your blood sugar control and diabetes risk."]
Key facts at a glance
- LOINC
- 33405-2
- Short code
- Glucose Pcar-mCnc
- Synonyms
- Glucose Pcar-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 This Test Matters
Your doctor may order this test to diagnose or monitor conditions like type 1 or type 2 diabetes, prediabetes, or to evaluate how well medications are working. It’s also used in screening for metabolic disorders or during pregnancy to check for gestational diabetes.
How the Test Works
A healthcare provider will draw blood from a vein in your arm while you’re fasting (typically 8–12 hours before the test). The blood sample is sent to a lab, where glucose levels are measured using an enzymatic method, which detects sugar presence without relying on specific numeric values.
What to Expect Before the Test
You’ll need to avoid eating or drinking anything except water for the specified fasting period. Wear comfortable clothing and let your provider know if you’re pregnant, have a history of bleeding disorders, or take blood-thinning medications.
What the Results Mean
Results are interpreted by your doctor based on your medical history and symptoms. While exact reference ranges vary by lab, high levels may indicate diabetes or insulin resistance, while low levels could signal hypoglycemia or other metabolic 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.
◆Associated findings1
Short name
Fasting Plasma Glucose
Frequently asked questions
Why was this test ordered?
What does a high or low result mean?
Do I need to prepare differently if I’m pregnant?
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