Insulin: normal range, high and low

In shortThere is no single normal range to compare against: an insulin result means nothing without the glucose measured at the same time. High insulin with normal glucose points to insulin resistance; high or normal insulin with low glucose points to too much insulin; low insulin with high glucose means the pancreas cannot make enough.

Check your value

Enter your result — we will show how it compares with a typical range. Match the units of the selected row.

Approximate comparison with a typical range, not a diagnosis. Reference intervals vary by laboratory and method — check your report; result interpretation is done by a doctor.

What this marker is

An insulin in blood test measures the amount of insulin in a blood sample. Insulin is a hormone made by the pancreas; it moves blood glucose from the bloodstream into the cells, where it is used for energy. Normally insulin and blood glucose rise and fall together: glucose increases after a meal, the pancreas releases more insulin, the insulin lets glucose into the cells, and as glucose returns to its normal range the insulin level decreases too.

Serious problems develop when the pancreas makes the wrong amount of insulin at the wrong time. Too much insulin leaves too little glucose in the blood — hypoglycemia, which in its severe form starves brain cells of glucose and needs immediate medical treatment. Too little insulin traps glucose in the bloodstream — hyperglycemia, which over time can lead to type 2 diabetes and its complications in the eyes, heart, and other parts of the body.

The test has four main uses, always in combination with other tests: finding the cause of hypoglycemia — the main reason for insulin testing; diagnosing insulin resistance, in which cells respond poorly to insulin and the pancreas compensates by making more, until it may wear out and prediabetes or type 2 diabetes follows; guiding treatment decisions in type 2 diabetes, including whether insulin itself needs to be part of treatment; and monitoring how well pancreatic islet cell transplantation is working in type 1 diabetes.

Preparation usually means fasting — no food or drink for 8 to 12 hours before the test. Biotin supplements (vitamin B7) and supplements that include biotin need to be stopped for at least a short time beforehand, on the provider's instructions.

Calculator: HOMA-IR

Enter fasting glucose and fasting insulin from your report — the calculator estimates insulin resistance.

HOMA-IR = glucose (mmol/L) × insulin (µIU/mL) / 22.5. Both values must be fasting. Everything runs in your browser.

When it is high

Insulin resistanceHigh insulin with a normal or slightly above-normal glucose level suggests the cells are not responding well to insulin, and the pancreas is compensating by making more.

Too much insulin for the glucose levelHigh or normal insulin with a low glucose level points to hypoglycemia from too much insulin. Possible causes include a pancreatic tumor (insulinoma), Cushing's syndrome, and taking too much insulin for diabetes.

When it is low

The pancreas cannot keep upLow insulin with a high glucose level may mean the pancreas cannot make enough insulin. Possible causes include type 1 diabetes and pancreatitis.

What can skew the result

These factors can shift the value without any disease — worth considering before a retest:

Food and drink within 8–12 hours before the testBiotin (vitamin B7) supplements and supplements containing biotinThe glucose level at the moment of the draw — insulin is interpreted only together with it

How to prepare

Fasting is usually required: no food or drink for 8 to 12 hours before the test. Biotin supplements (vitamin B7), or supplements that include biotin, are stopped beforehand for at least the period the provider specifies.

When a retest makes sense

Insulin is never interpreted alone — the provider considers the medical history and the results of other tests, including a blood glucose test from the same moment. There are other possible causes of abnormal insulin and glucose combinations, so the pairing of the two results is what directs the next step.

Who usually reviews this result

A result outside the reference range is usually reviewed by: an endocrinologist; your GP or primary care doctor for the first evaluation. Bring your lab report and any previous results to the appointment.

Names used on lab reports

Your report may use any of these names:
Fasting insulinInsulin serumTotal and free insulin

Units

Measured in: µIU/mL

Several markers on your report?

See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.

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Frequently asked questions

Why is there no normal range table on this page?

Because an insulin number is meaningless on its own. The same value can be appropriate or alarming depending on the blood glucose measured at the same time, so laboratories and providers interpret the pair together rather than a standalone range.

What does high insulin with normal glucose mean?

That pattern points to insulin resistance: the cells respond poorly to insulin, and the pancreas makes extra to keep glucose normal. Over time the pancreas may wear out, which can lead to prediabetes and then type 2 diabetes.

Why is biotin a problem for this test?

Biotin (vitamin B7), including supplements that contain it, can distort the insulin measurement, so it is stopped for a period before the blood draw on the provider's instructions.

Sources

Insulin in Blood: MedlinePlus Medical Test — MedlinePlus, National Library of Medicine. Accessed: August 29, 2026.

Insulin