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Glucose in Serum (Fasting) – Quantitative Measurement

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 identify conditions like diabetes or insulin resistance.

Quick summary

["A fasting blood sugar test checks if your body processes sugar normally."]

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

Key facts at a glance

LOINC
33110-8
Short code
GA from HC meas.Chitty97
Synonyms
GA from HC meas.Chitty97
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-hc-measured-chitty
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 diagnose or monitor conditions such as type 1 or type 2 diabetes, prediabetes, or to check for complications like high blood sugar over time. It’s also used before surgeries or during pregnancy to ensure safe blood sugar levels.

How the Test Works

A small sample of your blood is taken from a vein, usually in your arm. The sample is sent to a lab where glucose levels are measured using a specialized test method. Results are compared to standard reference ranges to determine your blood sugar status.

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 doctor will provide specific instructions. Avoid smoking or chewing gum during this time to ensure accurate results.

What to Expect During the Test

The test is quick and painless. A healthcare provider will clean the area with an antiseptic, insert a small needle into your vein, and collect a blood sample. You may feel a slight pinch, but the procedure usually takes only a few minutes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

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 doctor will contact you once they are ready to discuss the findings.
What do my results mean?
Your results will be compared to standard reference ranges provided by your lab. If your levels are outside the normal range, your doctor may recommend further testing or lifestyle changes to manage your blood sugar.
Can I eat or drink anything after the test?
Yes, you can resume your normal diet and activities immediately after the test. However, if you were instructed to fast, avoid eating or drinking anything except water until the test time is confirmed.
  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