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Insulin, Serum/Plasma

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

A blood test that measures insulin levels to help evaluate blood sugar regulation, insulin resistance, and diabetes.

Quick summary

["Insulin levels are most useful when interpreted together with blood glucose and other diabetes tests."]

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

Key facts at a glance

LOINC
27875-4
Short code
Insulin sp6 p chal SerPl-aCnc
Synonyms
Insulin sp6 p chal SerPl-aCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
2.6
Ref high
24.9
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
83525
SNOMED
413618004
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

What is this test?

This test measures the amount of insulin in blood. Insulin is a hormone made by the pancreas that helps glucose enter cells for energy.

Why might I need this test?

A clinician may order it when evaluating diabetes, insulin resistance, metabolic syndrome, symptoms of low blood sugar, or the body's response to glucose.

How is the test performed?

A blood sample is collected, usually by a venipuncture, and the insulin level is measured in a laboratory. The sample may be tested while fasting or at another specified time.

How do I prepare for the test?

Follow the preparation instructions provided by your clinician, which may include fasting for several hours. Do not stop or change insulin or other medicines unless your healthcare professional tells you to do so.

Reference range

Fasting: 2.6-24.9 μIU/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Higher insulin levels may occur with insulin resistance, excess body weight, metabolic syndrome, or early type 2 diabetes. Lower levels may occur when the pancreas produces too little insulin or after certain diabetes treatments. Results should be interpreted with blood glucose, symptoms, medications, and other relevant tests.

Short name

Insulin

Frequently asked questions

Is a fasting insulin test usually required?
It depends on the reason for testing. A fasting sample provides a baseline value, while a stimulated insulin test may be used to assess how the pancreas responds to glucose.
Can insulin levels diagnose diabetes by themselves?
No. Insulin is usually interpreted with fasting glucose, A1C, or glucose-tolerance test results rather than used alone to diagnose diabetes.
Do I need to stop taking insulin before the test?
Usually not. Do not change insulin or other diabetes medicines without medical guidance, because this could affect both your health and the interpretation of the 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