Fasting Insulin levels: what's normal, high and low
How much insulin your pancreas is releasing at rest. High values often indicate insulin resistance.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Fasting Insulin is measured with a standard blood draw after an 8–12 hour fast. A typical reference range is 2.00 – 20.0 uIU/mL. At TestWell it's $22.99 all-in as Insulin, Fasting, results in 2–4 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- uIU/mL / µIU/mL
- Sample
- Blood draw
- Fasting
- 8–12 hours
- Results
- 2–4 business days
- Price
- $22.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Fasting Insulin Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+, fasting | 2.00 – 20.0 uIU/mL |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
Have a result in hand? analyze it with your AI assistant using these reviewed ranges, or run it through our explainer. Tools: look up another marker's range · convert lab units
What your Fasting Insulin result may mean
Often reflects insulin resistance, prediabetes, or PCOS.
What a high Fasting Insulin means: causes, symptoms, next steps ↓Educational only — not a diagnosis. Many factors can influence a single result. Discuss anything that concerns you with a healthcare provider.
What does a high Fasting Insulin mean?
High fasting insulin means the pancreas is working harder to keep glucose normal — the hallmark of insulin resistance, which precedes prediabetes and type 2 diabetes by years. Excess weight (especially abdominal), inactivity, poor sleep, PCOS, fatty liver and some medications drive it. A non-fasting sample raises insulin dramatically, so the fast has to be real.
Common causes of a high Fasting Insulin
- Not fasting
- Insulin resistance from excess weight, inactivity, poor sleep
- PCOS
- Non-alcoholic fatty liver disease
- Medications: glucocorticoids, some antipsychotics
- Rare: insulinoma (with low glucose)
Ordered from most to least common.
Symptoms that can go with it
- Often none
- Weight gain around the middle, hunger soon after eating, afternoon energy crashes
- Skin tags, darkened skin folds (acanthosis nigricans)
What clinicians usually check next
- Fasting glucose and A1c (HOMA-IR can be calculated from glucose and insulin)
- Lipid panel and liver enzymes
- Repeat fasting if timing was uncertain
Follow-up tests at TestWell: Lipid Panel ($24.99), Glucose ($14.99).
What fasting insulin level is high?
Reference ranges go up to about 25 µIU/mL, but many clinicians consider values above 10–15 a sign of insulin resistance, especially with a HOMA-IR above about 2.5.
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
What does a low Fasting Insulin mean?
Low fasting insulin is normal in lean, insulin-sensitive people and after prolonged fasting. In someone with high glucose, a low insulin suggests the pancreas isn't producing enough — type 1 diabetes, late-stage type 2, pancreatic disease — and C-peptide helps confirm. On its own, with a normal glucose, it's reassuring rather than concerning.
Common causes of a low Fasting Insulin
- Normal insulin sensitivity
- Prolonged fasting
- Type 1 diabetes or advanced type 2 (with high glucose)
- Pancreatic disease
- Insulin degradation in a delayed sample
Ordered from most to least common.
Is a fasting insulin of 3 too low?
With a normal glucose, no — it indicates good insulin sensitivity. With a high glucose, it raises the question of insulin deficiency.
Educational only — not a diagnosis. A single result outside the range is a prompt to look closer with a clinician.
How do you get a Fasting Insulin test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Fasting Insulin is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Insulin, Fasting | This marker only | $22.99 |
| Diabetes Screening Panel | 3 tests | $59.99 |
| Pre-Diabetes Panel | 5 tests | $89.99 |
| Metabolism & Weight Loss Panel | 8 tests | $119.99 |
| GLP-1 Monitoring & Weight Management | 10 tests | $169.99 |
Quest vs. Labcorp for Fasting Insulin: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $22.99 |
| Labcorp | Yes | $23.99 |
| BioReference (NY & NJ) | Yes | $23.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Related Diabetes & Blood Sugar biomarkers
Markers commonly tested alongside Fasting Insulin.
Frequently asked
What does a high Fasting Insulin mean?
High fasting insulin means the pancreas is working harder to keep glucose normal — the hallmark of insulin resistance, which precedes prediabetes and type 2 diabetes by years. Excess weight (especially abdominal), inactivity, poor sleep, PCOS, fatty liver and some medications drive it. A non-fasting sample raises insulin dramatically, so the fast has to be real.
What fasting insulin level is high?
Reference ranges go up to about 25 µIU/mL, but many clinicians consider values above 10–15 a sign of insulin resistance, especially with a HOMA-IR above about 2.5.
What does a low Fasting Insulin mean?
Low fasting insulin is normal in lean, insulin-sensitive people and after prolonged fasting. In someone with high glucose, a low insulin suggests the pancreas isn't producing enough — type 1 diabetes, late-stage type 2, pancreatic disease — and C-peptide helps confirm. On its own, with a normal glucose, it's reassuring rather than concerning.
Is a fasting insulin of 3 too low?
With a normal glucose, no — it indicates good insulin sensitivity. With a high glucose, it raises the question of insulin deficiency.
Do I need a doctor's order to test my fasting insulin?
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
How long does it take to get Fasting Insulin results?
Most Fasting Insulin results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal.
How much does a Fasting Insulin test cost?
Our Insulin, Fasting starts at $22.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted.
Do I need to fast before my Fasting Insulin test?
Yes — for the most accurate result, fast for 8–12 hours before your blood draw. Water is fine; coffee, food, and supplements are not. Your prep instructions will be included with your order.
Which lab will process my Fasting Insulin test?
Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations.
What can throw off a Fasting Insulin result?
Eating before the draw, sleep deprivation and keto and high-protein diets can change a Fasting Insulin result without anything being wrong. Eating before the draw can raise Fasting Insulin — fast 8–12 hours; water only. Sleep deprivation can raise Fasting Insulin — avoid glucose and insulin testing after an all-nighter. Keto and high-protein diets can lower Fasting Insulin — none needed — expected improvement. Each is explained on our physician-reviewed "Before your test" pages; when one applies, remove it and retest.
Ready to test your fasting insulin?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $22.99.