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Glucose, Serum (Fasting) – Mass Concentration

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 glucose test is critical for detecting diabetes or prediabetes."]

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

Key facts at a glance

LOINC
50208-8
Short code
Glucose sp10 SerPl-mCnc
Synonyms
Glucose sp10 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

Your doctor may order this test to check for conditions like diabetes, high blood sugar, or metabolic disorders. It’s also used to monitor treatment progress for people already diagnosed with blood sugar-related conditions.

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, usually in your arm, by a phlebotomist.

How the Test Works

A small sample of your blood is taken and sent to a lab. The lab uses a specialized method to measure the exact amount of glucose in your serum, providing a precise reading.

What the Results Mean

Results help determine if your blood sugar is within a healthy range or if it’s too high or too low, which can indicate diabetes, insulin resistance, or other health issues.

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.

High fasting glucose levels may signal diabetes or insulin resistance, increasing risks for heart disease, nerve damage, and kidney problems. Low levels can cause fatigue, dizziness, or confusion. Regular monitoring helps manage these risks effectively.

Short name

Fasting Serum 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 time. Your healthcare provider will contact you with the final report.
What if my fasting glucose is higher than expected?
If your results are elevated, your doctor may recommend lifestyle changes (like diet and exercise), medications, or further testing to understand the cause and develop a treatment plan.
Can I eat or drink anything before the test?
No, you must fast for 8 to 12 hours before the test, including no food or liquids (except water) except for water. 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