HomeLab TestsInsulin in Blood
Back to Lab Tests
Insulin in Blood
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Insulin in Blood

An insulin in blood test measures how much insulin your pancreas is producing to help diagnose conditions like hypoglycemia, insulin resistance, and diabetes.

Overview

Insulin is a hormone produced by the pancreas that moves blood glucose (sugar) from your bloodstream into your cells for energy. Normally, insulin and glucose levels rise and fall in tandem: glucose rises after eating, triggering the pancreas to release insulin, which then lowers glucose levels back to a normal range.

Problems arise if the pancreas produces the wrong amount of insulin:

  • Too much insulin can lead to hypoglycemia (low blood glucose), which can prevent brain cells from functioning properly.
  • Too little insulin causes glucose to build up in the bloodstream, leading to hyperglycemia (high blood glucose), which can result in type 2 diabetes and complications in the heart, eyes, and other organs.

What is it used for?

This test is used to:

  • Identify the cause of hypoglycemia.
  • Diagnose insulin resistance, where cells do not respond well to insulin, potentially leading to prediabetes or type 2 diabetes.
  • Guide treatment decisions for type 2 diabetes.
  • Monitor the success of pancreatic islet cell transplantation in patients with type 1 diabetes.

Why do I need this test?

You may need this test if you have symptoms of hypoglycemia (sweating, shakiness, arrhythmia, confusion, dizziness, headache, or hunger), have a high risk for insulin resistance (due to PCOS, heart disease, or acanthosis nigricans), or have undergone pancreatic surgery, such as an insulinoma removal or islet cell transplantation.

Test Procedure and Preparation

The test involves a blood draw from a vein in your arm. You will likely need to fast for 8 to 12 hours beforehand. If you take biotin supplements, you must stop taking them for at least one day prior to the test, as they can interfere with results. Always consult your provider before stopping any medication.

Understanding Results

Results are interpreted alongside your medical history and blood glucose levels:

  • High insulin with normal/high glucose: May indicate insulin resistance.
  • High/normal insulin with low glucose: May indicate hypoglycemia caused by an insulinoma, Cushing's syndrome, or excessive insulin medication.
  • Low insulin with high glucose: May indicate the pancreas cannot produce enough insulin, as seen in type 1 diabetes or pancreatitis.

This test is often performed alongside a C-peptide test, which provides a more accurate measurement of how much insulin your pancreas is producing.

Frequently Asked Questions

Elevated fasting insulin with normal glucose suggests the body is producing more insulin to maintain normal glucose levels, a hallmark of insulin resistance. This pattern is often seen in conditions such as polycystic ovary syndrome, obesity, or early type 2 diabetes, and may prompt further testing or lifestyle interventions.
Yes. Weight loss, regular aerobic exercise, and a diet low in refined carbohydrates can improve insulin sensitivity, often lowering fasting insulin concentrations. Consistent monitoring can help gauge the effectiveness of these changes over time.===
Most clinicians ask patients to fast for 8 to 12 hours before the blood draw. During this period, you should avoid eating or drinking anything except water. Take your usual medications unless your doctor specifically tells you otherwise; some drugs (e.g., insulin, sulfonylureas, or certain steroids) can affect the results, so discuss this with your provider beforehand.
In suspected insulinoma, clinicians compare fasting insulin, C‑peptide, and proinsulin levels. A high insulin level with a proportionally high C‑peptide (indicating endogenous production) and a low glucose level points toward insulinoma, whereas low C‑peptide suggests exogenous insulin use or other causes.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

kontakt@hittavard.se

Ⓒ 2024. Alla rättigheter förbehålls av juxt ab

Sök
Om ossVillkor och policyVanliga frågorKontakta oss