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Glucose, Serum or Plasma (Concentration)

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

This test measures the amount of glucose (sugar) in your blood, drawn from either serum or plasma. Glucose is the primary energy source for your body’s cells.

Quick summary

["Check your blood sugar levels to manage energy, metabolism, and overall health."]

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

Key facts at a glance

LOINC
30263-8
Short code
Glucose 20M p Glc SerPl-sCnc
Synonyms
Glucose 20M 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 This Test Is Done

Doctors order glucose tests to monitor blood sugar levels for conditions like diabetes, prediabetes, or to assess how your body responds to medications or treatments. It may also be used during pregnancy, before surgeries, or to diagnose metabolic disorders.

What to Expect Before the Test

You may be asked to fast (not eat or drink except water) for several hours before the test, depending on the reason. If fasting is required, your provider will let you know. Bring any medications you’re currently taking.

How the Test Is Performed

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a quick pinch, but it usually doesn’t cause discomfort afterward. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results help determine if your blood sugar is too high or too low, which can indicate diabetes, insulin resistance, or other health issues. Your doctor will discuss these results with you and may recommend follow-up actions.

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

Glucose Level

Frequently asked questions

How often should I get this test?
Your doctor will determine the frequency based on your health condition, symptoms, and treatment plan. Regular monitoring is essential for managing chronic conditions like diabetes.
Can I eat or drink before this test?
If fasting is required, follow your doctor’s instructions carefully. If not, avoid sugary foods or drinks that could affect results. Always confirm with your provider.
What if my glucose level is unusually high or low?
Unusually high or low levels may signal an underlying health issue. Your doctor will review your results and may recommend lifestyle changes, medication adjustments, or further testing to address the concern.
  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