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Total Serum/Plasma Glucose (Fasting)

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

This test measures the amount of glucose (sugar) in your blood after you’ve fasted for 8–12 hours. It helps assess your blood sugar levels and identify conditions like diabetes or insulin resistance.

Quick summary

["A fasting blood sugar test checks for healthy glucose balance and potential diabetes risk."]

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

Key facts at a glance

LOINC
58000-1
Short code
Maple sugar IgE/IgE total %
Synonyms
Maple sugar IgE/IgE total %
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 like type 1 or type 2 diabetes, prediabetes, or other metabolic disorders. It’s also used to evaluate how your body responds to medications or treatments for blood sugar control.

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 in your arm by a healthcare professional. The process is quick and typically painless.

How the Test Works

A small sample of your blood is taken and sent to a lab. There, glucose levels are measured using an enzymatic method, which detects the sugar’s presence and concentration in your bloodstream.

What the Results Mean

Results are compared to standard reference ranges, but your doctor will interpret them based on your medical history and symptoms. High or low levels may signal underlying health concerns that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Fasting Blood Sugar

Frequently asked questions

What does a normal fasting blood sugar level mean for me?
A normal result doesn’t mean you’re completely healthy—your doctor will consider your overall health, symptoms, and other test results. If your result is outside the typical range, you may need additional testing or follow-up.
How long will I need to wait for my results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will contact you with the final interpretation, so check with them for updates.
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 may 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