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Glucose, 3-Hour Postprandial (Plasma)

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

This test measures your blood sugar level three hours after eating to assess how your body handles glucose over time.

Quick summary

["Helps diagnose and monitor diabetes and glucose metabolism disorders."]

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

Key facts at a glance

LOINC
42604-9
Short code
Glucose 3h p Lac PO Ur-mCnc
Synonyms
Glucose 3h p Lac PO Ur-mCnc
Category
glucose
Sample
urine
Container
Sterile urine container
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
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test if you have symptoms of diabetes (like frequent urination, extreme thirst, or unexplained weight loss), if you have a family history of diabetes, or if you’re at risk due to other health conditions. It’s also used to check how well diabetes medications or insulin are working.

What to Expect Before the Test

You’ll typically fast overnight (usually 8–12 hours) before this test. On the day of the test, avoid eating or drinking anything except water. Bring your fasting blood sugar results if you’ve had them recently.

During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause significant discomfort. The blood is collected in a plasma specimen for analysis.

After the Test

You can resume eating and drinking normally after the test. Apply gentle pressure to the site to stop bleeding, and check for any signs of infection (redness, swelling, or pus). Report any unusual symptoms to your provider.

Reference range

Fasting: 70-100 mg/dLN/A

Specimen: urine

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.

This test is critical for diagnosing type 2 diabetes, prediabetes, or gestational diabetes. Abnormally high or low levels can indicate poor glucose control, which may require lifestyle changes, medication adjustments, or further testing (like an oral glucose tolerance test).

Short name

3-Hour Blood Sugar (Plasma)

Frequently asked questions

What Does a High or Low Glucose Level Mean?
High glucose levels may suggest diabetes or insulin resistance. Low levels (hypoglycemia) can cause shakiness, dizziness, or confusion. Your provider will discuss results and next steps with you.
Do I Need to Fast for This Test?
Yes, fasting is required. Follow your provider’s instructions about when to stop eating/drinking before the test.
How Long Does It Take to Get Results?
Results are usually available within 1–3 business days, depending on your lab’s processing time.
  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