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IGF-1 (Insulin-like Growth Factor 1) Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

IGF-1 (Insulin-like Growth Factor 1) Test

The IGF-1 test measures a hormone in your blood that manages the effects of growth hormone (GH) to promote bone and tissue development.

What is an IGF-1 test?

IGF-1 is a hormone that works with growth hormone (GH) to manage growth and metabolism. Because GH levels fluctuate throughout the day, IGF-1 levels are measured as a more stable indicator of GH activity in the body.

What is it used for?

The test is used to detect and monitor growth hormone disorders, including:

  • GH deficiency: Causes slow growth in children and low bone density or muscle mass in adults.
  • GH insensitivity (Laron syndrome): A rare genetic disorder where the body cannot use the GH it produces.
  • Gigantism: A rare childhood disorder involving excess GH, leading to excessive height and large extremities.
  • Acromegaly: An adult condition involving excess GH, leading to thickened bones and enlarged facial features.

What happens during the test?

A health care professional will take a blood sample from a vein in your arm using a small needle. The procedure typically takes less than five minutes and requires no special preparation.

Understanding Results

  • Lower than normal levels: In children, this may indicate GH deficiency or insensitivity, which may be treated with GH supplementation. In adults, it may be age-related or due to other conditions.
  • Higher than normal levels: May indicate gigantism or acromegaly, often caused by a pituitary gland tumor. Treatment may include surgery, radiation, or medication.

Related Tests

Your provider may also order:

  • GH stimulation test: To diagnose deficiency or insensitivity.
  • GH suppression test: To diagnose excess GH.
  • IGBP-3 test: To help diagnose GH-related disorders by measuring the protein that carries IGF-1.

Frequently Asked Questions

n elevated IGF‑1 that persists on repeat testing warrants a pituitary MRI with contrast to look for adenomas or other sellar lesions. Depending on the MRI findings, a GH suppression test (oral glucose tolerance test) may be performed to confirm autonomous GH secretion.
Generally, fasting is not required for an IGF‑1 draw, and most routine medications can be continued. However, oral estrogen, glucocorticoids, and certain diabetes drugs can affect IGF‑1 levels, so inform your clinician. They may ask you to hold hormone therapy for a few weeks if the result will guide a pituitary work‑up.
Several factors can skew IGF‑1: chronic liver disease, malnutrition, uncontrolled diabetes, severe renal failure, and acute illness can lower IGF‑1. Conversely, pregnancy, high estrogen states (e.g., oral contraceptives), and acute inflammation can raise IGF‑1 modestly. Always interpret the value in the clinical context.
Most endocrinologists monitor IGF‑1 every 3–6 months after initiating therapy, then annually once a stable dose is achieved. The goal is to keep IGF‑1 within the age‑adjusted reference range (typically between the 25th and 75th percentile) to balance efficacy and safety.
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.

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