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Glucose in Serum (or Plasma)

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

This test measures the amount of glucose, a type of sugar, in your blood. Glucose levels help doctors assess how well your body is using food for energy.

Quick summary

["This test helps monitor blood sugar control, especially important for managing diabetes or other conditions affecting metabolism."]

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

Key facts at a glance

LOINC
87970-0
Short code
Gie Stn Amn
Synonyms
Gie Stn Amn
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
giemsa-stain
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your healthcare provider may order this test to check for diabetes, monitor blood sugar levels over time, or evaluate how well medications are working to control glucose. It’s also used before surgeries or during pregnancy to ensure stable blood sugar.

What to Expect Before the Test

You may be asked to fast (not eat or drink except water) for 8–12 hours before the test, depending on your doctor’s instructions. Bring any medications you’re taking to your appointment.

How the Test Is Performed

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

What the Results Mean

Results are typically reported in milligrams per deciliter (mg/dL). High or low glucose levels can signal diabetes, insulin issues, or other health concerns that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum/Plasma Glucose

Frequently asked questions

What causes glucose levels to be too high?
High glucose levels can result from diabetes, poor diet, stress, illness, or certain medications. If you suspect this, discuss your symptoms with your doctor to explore possible causes.
What if my glucose test is abnormal?
If your results are outside normal ranges, your doctor may recommend follow-up tests, lifestyle changes, or adjustments to your treatment plan. They’ll work with you to address any concerns.
Can I eat or drink before this test?
Check with your doctor or lab about fasting requirements. Some tests require fasting, while others allow water or specific foods. Always follow their instructions to get accurate 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