Fasting Glucose by Enzymatic Method (Serum)
This test measures the amount of glucose (sugar) in your blood after you’ve fasted for 8–12 hours. It helps check how well your body uses sugar for energy.
["A fasting blood glucose test helps diagnose diabetes or prediabetes and monitor blood sugar levels."]
Key facts at a glance
- LOINC
- 11924-8
- Short code
- GA from FL.Merz87
- Synonyms
- GA from FL.Merz87
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- us-estimated-from-fl-merz
- 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 Is This Test Done?
Your doctor may order this test if you have symptoms like excessive thirst, frequent urination, unexplained weight changes, or fatigue. It’s also used to screen for diabetes or monitor conditions like prediabetes, gestational diabetes, or diabetes management in people with existing health issues.
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 or lab technician will explain the fasting period and any special instructions. Bring your appointment details and any medications you’re currently taking.
What Happens During the Test
A healthcare provider will draw blood from a vein in your arm using a small needle. You may feel a quick pinch, but it usually doesn’t cause discomfort. The blood sample is sent to a lab for analysis.
What the Results Mean
Results are typically reported in milligrams per deciliter (mg/dL). A high result may indicate diabetes or insulin resistance, while a low result could suggest conditions like hypoglycemia (low blood sugar). Your doctor will interpret the results in the context of your overall health.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
High fasting blood glucose levels are a key diagnostic marker for diabetes. Repeatedly elevated results may require further testing, such as an oral glucose tolerance test, to confirm diabetes. Regular monitoring helps manage blood sugar levels and prevent complications like nerve damage, kidney disease, or heart problems.
Short name
Fasting Blood Glucose
Frequently asked questions
How long does it take to get my results?
Can I eat or drink anything before the test?
What if I take diabetes medication 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