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Glucose (Plasma or Serum) by Enzymatic Method

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

This test measures the amount of glucose, a type of sugar, in your blood plasma or serum. It helps assess your blood sugar levels.

Quick summary

["Glucose levels can indicate how well your body is managing energy and diabetes control."]

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

Key facts at a glance

LOINC
40217-2
Short code
Glucose 28h p chal SerPl-sCnc
Synonyms
Glucose 28h p chal SerPl-sCnc
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

Doctors order glucose tests to monitor blood sugar levels for conditions like diabetes, detect prediabetes, or evaluate symptoms such as excessive thirst, frequent urination, or unexplained weight changes. It may also be used during pregnancy to check for gestational diabetes or before certain surgeries.

What to Expect Before the Test

For fasting tests, you’ll typically fast for 8–12 hours before the blood draw. If not fasting, your doctor may instruct you to eat a standard meal beforehand. Avoid smoking or caffeine 30 minutes before the test. Bring any medications you’re taking to discuss with your healthcare provider.

How the Test Is Performed

A healthcare professional will insert a small needle into a vein in your arm or hand to collect a blood sample. The blood is then sent to a lab for analysis using an enzymatic method, which measures glucose activity in the sample.

What the Results Mean

Results are compared to standard reference ranges, but your specific values will be interpreted by your doctor based on your overall health and medical history. High or low glucose levels may signal diabetes, metabolic issues, or other health concerns.

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

Short name

Glucose

Frequently asked questions

What could cause abnormal results?
Abnormally high glucose levels may indicate diabetes, poor insulin function, or stress-related spikes. Low levels can result from insulin overdose, severe illness, or inadequate food intake. Other factors like medications, infections, or recent physical activity can also affect results.
How often should I get this test?
Your doctor will determine the frequency based on your health needs. For diabetes management, tests may be done monthly or more often during unstable periods. Follow-up schedules vary by condition and individual health status.
Can I eat or drink before the test?
For fasting tests, avoid food or liquids (except water) for the specified duration. If your test isn’t fasting-based, follow your doctor’s instructions. Never consume alcohol or smoke before the test.
  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