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Glucose, 30-Minute Postprandial (Serum)

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

This test measures your blood sugar level taken 30 minutes after you’ve eaten a meal. It helps doctors assess how well your body handles glucose after digestion.

Quick summary

Understanding how your body responds to food can help manage blood sugar levels over time.

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

Key facts at a glance

LOINC
39998-0
Short code
Glucose 30M pre chal SerPl-mCnc
Synonyms
Glucose 30M pre chal SerPl-mCnc
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 Is This Test Done?

Your doctor may order this test if they suspect you have diabetes or prediabetes, or if you have symptoms like frequent thirst, fatigue, or unexplained weight changes. It can also help monitor how well diabetes treatments are working.

What to Expect Before the Test

You’ll need to fast for about 8 to 12 hours before the test, but you can drink water. On the day of the test, eat a standard meal (about 500–750 calories) and have the blood drawn 30 minutes later. Bring any medications you’re taking with you.

How the Test Works

A healthcare provider will draw blood from a vein in your arm. The blood sample is sent to a lab where glucose levels are measured using an enzymatic method. The result reflects your blood sugar level at that specific time after eating.

What the Results Mean

Results are typically reported in milligrams per deciliter (mg/dL). While exact ranges vary by lab, higher than expected levels may indicate poor glucose control, while lower levels could suggest issues like hypoglycemia or medication side effects.

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.

Clinical Significance: Glucose Monitoring in Diabetes and Metabolism

Short name

Glucose (30 min after eating)

Frequently asked questions

How soon after eating should I expect the blood draw?
The blood draw will occur exactly 30 minutes after you finish your meal. Your doctor or lab technician will guide you on timing to ensure accurate results.
Can I take my diabetes medication before the test?
If you take insulin or certain oral diabetes medications, you may need to adjust your dose or skip it on the day of the test. Always follow your doctor’s specific instructions to avoid affecting the results.
What if I feel dizzy or lightheaded before the blood draw?
It’s normal to feel a bit shaky before a blood draw, especially if you haven’t eaten recently. Drink water, take a deep breath, and let your healthcare provider know if symptoms persist. They may help you sit or lie down until you feel better.
  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