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Glucose in Serum (Fasting or Random) – Differential Measurement

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

This test measures glucose levels in your blood serum, often used to assess blood sugar control, especially in diagnosing or monitoring diabetes or other metabolic conditions.

Quick summary

["Glucose levels help track how your body processes sugar, critical for managing diabetes or detecting potential metabolic issues."]

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

Key facts at a glance

LOINC
72651-3
Short code
Glucose ser - plr fld-SCDiff
Synonyms
Glucose ser - plr fld-SCDiff
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 This Test Is Done

Your healthcare provider may order this test to check for diabetes, monitor blood sugar levels over time, or evaluate conditions like hypoglycemia (low blood sugar), liver disease, or kidney problems. It may also be used in screening or during pregnancy to assess glucose metabolism.

How the Test Works

A blood sample is drawn from a vein, usually in your arm. The serum portion (liquid part after clotting) is analyzed to measure glucose concentration using a sensitive laboratory method, often an enzymatic assay. Results may be reported as a single value or compared to prior measurements.

What to Expect Before the Test

For fasting glucose tests, you’ll typically fast (no food or drink except water) for 8–12 hours before the test. For random glucose tests, no fasting is required. Always follow your provider’s specific instructions to ensure accurate results.

What to Expect During the Test

You’ll lie down or sit comfortably while a healthcare provider inserts a small needle into a vein in your arm. A small amount of blood is collected into a tube. The process usually takes a few minutes and may cause mild discomfort or bruising.

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.

◆Associated findings1

Frequently asked questions

What does a high or low glucose level mean?
A high glucose level may suggest diabetes, poor blood sugar management, or conditions like pancreatitis or Cushing’s syndrome. A low glucose level could indicate hypoglycemia, insulin overuse, or certain endocrine disorders. Your results will be interpreted by your healthcare provider in the context of your overall health.
How often should I get this test?
Frequency depends on your health status. People without diabetes may get a baseline test occasionally, while those with diabetes or prediabetes often have tests every 3–6 months. Your provider will determine the best schedule for you based on your medical history and needs.
Can lifestyle changes affect this test result?
Yes, diet, exercise, and stress can impact blood sugar levels. For fasting tests, avoid eating or drinking (except water) before the appointment. If you’re unsure about recent activities, discuss them with your provider to ensure 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