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Glucose (Serum or Plasma) by Enzymatic Method

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

This test measures the amount of glucose, a type of sugar, in your blood. It helps doctors check how well your body is using sugar for energy and monitor conditions like diabetes.

Quick summary

["A glucose test helps track blood sugar levels and support diabetes management or other health conditions."]

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

Key facts at a glance

LOINC
14757-9
Short code
Glucose 2h p 100 g Glc PO SerPl-sCnc
Synonyms
Glucose 2h p 100 g Glc PO 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

Your healthcare provider may order this test to diagnose or monitor conditions such as diabetes, hypoglycemia (low blood sugar), or to check for metabolic issues. It can also be used during pregnancy, before surgeries, or to evaluate symptoms like excessive thirst, frequent urination, or unexplained weight changes.

How the Test Is Performed

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where an enzymatic method is used to measure glucose concentration. The result is reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).

What the Results Mean

Results can vary based on your health status, diet, activity level, and time since last meal. For example, normal glucose levels may differ slightly between adults and children, and fasting vs. non-fasting samples can affect readings.

Common Conditions Monitored

High glucose levels may indicate diabetes or prediabetes, while low levels can signal hypoglycemia. Chronic high levels can damage blood vessels and nerves over time, increasing risks for heart disease, kidney problems, or nerve damage.

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 Level

Frequently asked questions

Will fasting be required before this test?
Yes, fasting is often recommended for glucose tests to get an accurate reading. If you have diabetes or are unsure, ask your healthcare provider about whether you should fast or take your usual medications before the test.
Can I eat or drink anything before the test?
Typically, you should avoid food for at least 8–12 hours before the test, but you may drink water unless instructed otherwise. Some tests may allow a small amount of clear liquids if specified by your provider.
What are the typical reference ranges for this test?
Reference ranges can vary by lab and individual factors. For adults, fasting glucose levels are often considered normal at below 100 mg/dL, while non-fasting levels may range up to 140 mg/dL. Always check with your healthcare provider for your specific 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