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Glucose in Serum or Plasma (24-hour profile)

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

This test measures your blood glucose levels over a 24-hour period, taken from either your blood serum or plasma, to help assess how your body manages sugar (glucose) throughout the day.

Quick summary

["Understanding your natural blood sugar patterns helps doctors diagnose diabetes, insulin resistance, or other metabolic conditions."]

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

Key facts at a glance

LOINC
50589-1
Short code
GTT 6h Pnl SerPl
Synonyms
GTT 6h Pnl SerPl
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

Your doctor may recommend this test if they suspect you have diabetes, prediabetes, or another condition affecting how your body processes glucose. It’s also useful for monitoring long-term blood sugar control in people with diabetes.

How the Test Works

Blood samples are collected at regular intervals (often every 2–4 hours) over 24 hours. The glucose levels in each sample are measured using an immunoassay or enzymatic method to detect the sugar content.

What to Expect Before the Test

You’ll need to fast overnight before the first sample is taken, but after that, you can eat and drink normally. Some labs may require you to stay at the facility for the full 24 hours, while others may send you home with instructions to collect samples at home.

What the Results Mean

The results show your glucose levels at different times of day, helping identify patterns like spikes after meals or low levels during certain hours. Abnormal patterns may indicate insulin issues, stress responses, or other health concerns.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

24-Hour Glucose Profile

Frequently asked questions

What questions might you have about this test?
This test is primarily used to diagnose or monitor conditions like diabetes, hypoglycemia, or reactive hypoglycemia. It helps doctors see how your body naturally regulates blood sugar, which can guide treatment plans.
Will I need to fast before the test?
Yes, you’ll typically need to fast for 8–12 hours before the first sample is taken. After that, you can eat and drink normally, but avoid sugary foods or drinks that could affect results.
How often will I have blood drawn?
Blood is drawn at set intervals (e.g., every 2–4 hours) over 24 hours. Some labs may use a catheter for continuous monitoring, while others require multiple separate draws.
  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