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Glucose in Whole Blood (Fasting or Random)

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

This test measures the amount of glucose (sugar) in your blood, which helps doctors check for diabetes, high or low blood sugar, or other health conditions.

Quick summary

["This test helps monitor blood sugar levels and identify potential diabetes or metabolic issues."]

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

Key facts at a glance

LOINC
58091-0
Short code
G6PD NBS pnl DBS
Synonyms
G6PD NBS pnl DBS
Category
glucose
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
true
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 Is Done

Doctors may order this test to diagnose or manage diabetes, check for hypoglycemia (low blood sugar), evaluate metabolic disorders, or assess how your body processes glucose before surgery or during pregnancy.

What to Expect Before the Test

You may need to fast (not eat or drink anything except water) for 8–12 hours before the test if it’s a fasting glucose check. For random glucose tests, you can eat normally. Bring any medications you’re taking with you.

How the Test Is Performed

A healthcare provider will prick your finger to collect a small blood sample. The sample is sent to a lab where glucose levels are measured using an enzymatic method.

What the Results Mean

Results are typically reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). High results may indicate diabetes or insulin resistance, while very low results could signal hypoglycemia.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test plays a critical role in diagnosing diabetes, assessing blood sugar control in patients with existing conditions, and guiding treatment plans like insulin therapy or lifestyle changes.

Short name

Blood Glucose

Frequently asked questions

How often should I get this test if I have diabetes?
If you have diabetes, your doctor may recommend regular testing—sometimes daily or monthly—to track your blood sugar levels and adjust treatments as needed. Follow your healthcare provider’s specific schedule.
Can I eat or drink anything before a fasting glucose test?
For fasting tests, avoid food and liquids (except water) for 8–12 hours before the test. For random tests, no restrictions apply, but always confirm with your doctor.
What if my blood sugar is too high or too low?
High results may require lifestyle changes (like diet or exercise) or medication. Low results could mean you need a snack or medical attention, especially if symptoms like shakiness or dizziness occur.
  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