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Fasting Plasma Glucose (Serum) by Enzymatic Method

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

This test measures your blood sugar level after you’ve fasted for at least 8 hours. It helps assess your blood sugar control and identify diabetes or prediabetes.

Quick summary

["A fasting blood sugar test checks if your blood sugar is within a healthy range when you haven’t eaten."]

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

Key facts at a glance

LOINC
6764-5
Short code
Glucose p fast Ur Ql Strip
Synonyms
Glucose p fast Ur Ql Strip
Category
glucose
Sample
urine
Container
Sterile urine container
Units
N/A
Ref low
10
Ref high
40
Critical range
50 N/A – 400 N/A
Fasting
true
Population
adult
Sex
all
Age range
18–65 years
Method
test-strip
CPT
84484
SNOMED
302774002
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 doctor may order this test to diagnose diabetes, check how well diabetes treatments are working, or evaluate your risk for developing diabetes. It’s also used to monitor conditions like prediabetes or metabolic disorders.

What to Expect Before the Test

You’ll need to fast (not eat or drink anything except water) for 8 to 12 hours before the test. Your blood will be drawn from a vein, usually in your arm, by a healthcare professional.

How the Test Works

A small amount of blood is taken from a vein and sent to a lab. The lab uses an enzymatic method to measure glucose levels in your plasma or serum.

What the Results Mean

Results help determine if your blood sugar is too high or too low. For example, high levels may indicate diabetes, while consistently low levels could signal hypoglycemia or other health issues.

Reference range

Adult: 10-40 U/LN/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.

◆Associated findings1

Short name

Fasting Blood Sugar

Frequently asked questions

What causes fasting blood sugar to be high?
Factors like diabetes, obesity, poor diet, lack of exercise, stress, or certain medications can raise fasting blood sugar levels. If you suspect these may apply to you, discuss them with your doctor.
What should I do if my fasting blood sugar is high?
If your results are high, follow your doctor’s recommendations, which may include lifestyle changes (like diet and exercise), medication adjustments, or monitoring for other health conditions.
Can I drink water before the test?
Yes, you can drink plain water before the test, but avoid eating or drinking anything else, including juice or coffee, for the required fasting period.
  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