Insulin, Pre-12-Hour Fast, Serum/Plasma — Concentration
Measures the amount of insulin in a blood sample taken after an overnight fast to help evaluate how the body regulates blood glucose.
["Fasting insulin helps assess insulin production and how effectively the body responds to insulin."]
Key facts at a glance
- LOINC
- 30363-6
- Short code
- Insulin p 12h fast SerPl-aCnc
- Synonyms
- Insulin p 12h fast SerPl-aCnc
- Category
- hormone
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84484
- SNOMED
- 302774002
- 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 insulin, a hormone made by the pancreas that helps move glucose from the bloodstream into cells for energy. The sample is generally collected at the end of an overnight fast and is often interpreted alongside a simultaneous glucose test.
Why might I need this test?
A clinician may order fasting insulin to help evaluate insulin resistance, unexplained changes in blood glucose, diabetes risk, or how the body is responding to treatment. It may also be used when symptoms suggest too much or too little insulin.
How is the test performed?
A healthcare professional draws a small amount of blood from a vein into a serum or plasma tube. The laboratory then measures the concentration of insulin in the sample.
How do I prepare for the test?
Fast for the period specified by your clinician, commonly 8 to 12 hours, and have the blood drawn in the morning. Water is usually allowed, but follow the laboratory's instructions. If you have diabetes or take medicines that affect blood glucose, ask your clinician how to adjust them; do not stop prescribed treatment unless advised.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A higher-than-expected fasting insulin level may indicate that the body is producing more insulin because cells are responding poorly to it, which can occur with insulin resistance, obesity, or metabolic syndrome. A lower level may occur with prolonged fasting, certain medicines, or reduced insulin production. Results should be interpreted with fasting glucose, medical history, medications, and the laboratory's reference range.
Short name
Fasting insulin
Frequently asked questions
Is fasting insulin the same as an insulin tolerance test?
Why is my insulin result measured with fasting glucose?
Can medicines or illness affect fasting insulin?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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 17, 2026. · Read our editorial policy