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Glucose, fasting, measured in serum/plasma at 8 AM

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

This test checks your blood sugar level after you’ve gone without food for at least 8 hours. It helps doctors monitor blood sugar control, especially for conditions like diabetes.

Quick summary

["A fasting blood sugar test helps assess your risk for diabetes or manage existing blood sugar levels."]

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

Key facts at a glance

LOINC
48986-4
Short code
Glucose 8 AM SerPl-mCnc
Synonyms
Glucose 8 AM SerPl-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 Is This Test Done?

Doctors order this test to diagnose diabetes or prediabetes, check how well diabetes treatments are working, or evaluate symptoms like extreme hunger, fatigue, or frequent urination that might suggest high blood sugar.

What to Expect Before the Test

You’ll need to fast (not eat or drink anything except water) for 8 to 12 hours before the test. Your blood will be drawn from a vein in your arm by a healthcare professional.

What Happens During the Test?

A small needle will be inserted to draw a blood sample. You may feel a slight pinch, but it usually takes only a few seconds. The blood is then sent to a lab for analysis.

What Does the Test Result Mean?

Results are used to determine if your blood sugar is consistently high or low, which can indicate diabetes or other metabolic conditions. Your doctor will interpret the results in the context of your overall health.

Reference range

Fasting: 70-100 mg/dLN/A

Specimen: serum

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 Serum/Plasma Glucose

Frequently asked questions

How long does it take to get my results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing schedule. Your doctor will contact you with the final report.
Can I eat or drink anything before this test?
No, you must fast for 8 to 12 hours before the test. Only water is allowed during this period.
What if I feel dizzy or lightheaded after the blood draw?
You may experience a brief moment of discomfort or lightheadedness, but it usually passes quickly. If you feel unwell, rest for a few minutes and inform your doctor if symptoms persist.
  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