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Glucose in Serum or Plasma (24-hour average)

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

This test measures the average level of glucose (sugar) in your blood over a 24-hour period, using a sample of your serum or plasma.

Quick summary

["Understanding your long-term blood sugar helps manage diabetes and prevent complications."]

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

Key facts at a glance

LOINC
33858-2
Short code
GH SerPl-aCnc
Synonyms
GH SerPl-aCnc
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 for Diabetes Management

Unlike a single blood sugar check, this test provides insight into how consistently your blood sugar stays within healthy ranges over time. It’s especially useful for people with diabetes to track trends and adjust treatment plans.

How the Test Works

Your healthcare provider will collect a blood sample (serum or plasma) and analyze it using a specialized method to estimate your average blood sugar over 24 hours. The result reflects your body’s glucose metabolism over time.

What the Results Mean

Results are typically reported as a numerical value representing your average blood sugar concentration. While exact reference ranges vary by lab, higher values may indicate poor blood sugar control, while lower values could suggest hypoglycemia or other metabolic issues.

Common Causes of Abnormal Results

Elevated results may be linked to diabetes, poor diet, stress, or certain medications. Lower results could stem from overmedication, fasting, or underlying conditions like hypoglycemia. Always discuss results with your doctor.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

24-Hour Average Blood Sugar

Frequently asked questions

How often do I need this test?
Your doctor will determine how frequently this test is needed based on your health status, diabetes management plan, and other factors like medication adjustments or symptoms. Regular follow-ups help monitor long-term blood sugar trends.
What do I do if my results are out of range?
If your results are high, work with your healthcare team to adjust diet, exercise, or medication. If low, avoid eating or drinking until levels stabilize, and seek medical advice immediately if symptoms like dizziness or confusion occur.
Can I fast before this test?
Typically, fasting is not required for this test, as it measures average blood sugar over 24 hours. However, always confirm with your lab or doctor, as some facilities may have specific instructions.
  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