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Glucose, Serum (Fasting, 10 AM)

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

This test measures your blood sugar level after you’ve fasted for 8–12 hours. It helps your doctor assess how well your body uses glucose for energy.

Quick summary

["A fasting blood sugar test checks if your glucose levels are within a healthy range after resting from food."]

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

Key facts at a glance

LOINC
16165-3
Short code
Glucose 10 AM SerPl-mCnc
Synonyms
Glucose 10 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 This Test Matters

Fasting glucose testing is critical for diagnosing conditions like diabetes or prediabetes. It helps prevent long-term complications by identifying whether your body struggles to regulate blood sugar properly.

What to Expect Before the Test

You’ll need to fast (no food or drink except water) for 8–12 hours before your blood draw. Your doctor or lab will provide specific instructions based on your medical needs.

How the Test Works

A healthcare provider will draw blood from a vein in your arm. The sample is sent to a lab where glucose levels are measured using an enzymatic method to detect sugar in your serum.

What the Results Mean

Results help determine if your glucose levels are too high or too low, which can signal diabetes, insulin resistance, or other metabolic issues. Your doctor will interpret the results in relation to your symptoms and medical history.

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 Glucose

Frequently asked questions

Why is fasting required for this test?
Fasting ensures your blood sugar reflects your body’s natural glucose levels without recent food intake, giving a more accurate picture of how your body processes sugar.
What if I accidentally eat or drink something before the test?
You must follow your doctor’s fasting instructions strictly. If you miss fasting, the results may be unreliable, and your doctor may need to reschedule the test.
How long will I need to fast before the test?
Typically, you should fast for 8–12 hours, meaning no food or liquids (except water) since midnight or the time your doctor specifies.
  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