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Glucose (Fasting) – Serum or Plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of glucose (sugar) in your blood after you’ve fasted for at least 8 hours. It helps assess your blood sugar levels and overall metabolic health.

Quick summary

["A fasting blood glucose test checks if your body processes sugar normally and helps detect diabetes or prediabetes early."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
59813-6
Short code
Glucose 7 AM BldC Glucomtr-sCnc
Synonyms
Glucose 7 AM BldC Glucomtr-sCnc
Category
glucose
Sample
whole-blood
Container
Lavender-top (EDTA)
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
Method
glucometer
CPT
82947
SNOMED
260395008
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Matters

Your doctor may order this test to check for diabetes, monitor blood sugar control in people with diabetes, or evaluate symptoms like excessive thirst, fatigue, or unexplained weight changes. It’s also used during pregnancy to screen for gestational diabetes.

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 blood will be drawn from a vein, usually in your arm. The process is quick and typically painless.

What the Results Mean

Results are interpreted by your healthcare provider based on your medical history and symptoms. Abnormal results may prompt further testing, such as an oral glucose tolerance test or hemoglobin A1c.

Common Reasons for Testing

This test is commonly done if you have symptoms of high or low blood sugar, a family history of diabetes, or if you’re at higher risk due to age, obesity, or certain health conditions.

Reference range

Fasting: 70-100 mg/dLN/A

Specimen: whole-blood

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

Short name

Fasting Blood Glucose

Frequently asked questions

How often should I get this test?
The frequency depends on your health status. People without diabetes may get this test every 1–3 years as a routine check. Those with diabetes typically check it more often (e.g., every 3–6 months) to manage their condition.
What if my fasting blood glucose is high?
If your result is above the normal range, your doctor may recommend lifestyle changes (like diet and exercise), medications, or further testing to confirm diabetes or other conditions.
Can I eat or drink anything before the test?
No, you must fast for 8–12 hours before the test. Only water is allowed. Skipping this step can affect the accuracy of your results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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