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Glucose (Serum or Plasma)

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

This test measures the amount of glucose, a type of sugar, in your blood. It helps doctors monitor blood sugar levels, often used in diabetes management or general health assessments.

Quick summary

["Glucose levels can indicate diabetes risk, metabolic health, or other conditions requiring blood sugar tracking."]

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

Key facts at a glance

LOINC
25677-6
Short code
Glucose 6h p Glc SerPl-sCnc
Synonyms
Glucose 6h p Glc SerPl-sCnc
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 Is This Test Done?

Doctors may order this test to check for diabetes, monitor blood sugar control in people with diabetes, evaluate symptoms like excessive thirst or fatigue, or assess metabolic health. It can also be part of routine check-ups or before certain treatments.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast (not eat) for 8–12 hours before the test if it’s a fasting glucose check. Bring any medications you’re taking and let your healthcare provider know about recent illnesses or medications.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The sample is sent to a lab for analysis. The test is quick but may cause a slight pinch or discomfort at the injection site.

What Are the Results Mean?

Results are typically reported as a concentration (e.g., milligrams per deciliter or millimoles per liter). Your doctor will interpret the results in relation to your health history and symptoms. Abnormal results may trigger further testing or follow-up.

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

None

Frequently asked questions

How often should I get this test?
Frequency depends on your health status. People without diabetes may get this test once every few years as part of routine check-ups. Those with diabetes may need it monthly, quarterly, or more often based on their doctor’s recommendations.
What can affect my glucose test results?
Fasting status (eating or drinking before testing), recent illnesses, stress, medications (like steroids or diabetes drugs), or certain foods (e.g., high-sugar snacks) can influence results. Always follow your doctor’s instructions for accurate results.
Can I eat or drink anything before this test?
For fasting tests, avoid food and liquids (except water) for 8–12 hours before drawing blood. If your test isn’t fasting-based, your doctor will specify any restrictions.
  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