Who orders IGF-1 tests and what they are looking for

IGF-1 (in plain English: insulin-like growth factor 1) is a blood marker that tells a clinician how active your growth hormone system is. It is a targeted test, not a routine one — so knowing who orders it, and why, helps you tell a useful panel apart from an unnecessary one.

Who orders IGF-1 tests

Endocrinologists, primary care physicians, and longevity-focused clinicians are the main people who order IGF-1 tests. They reach for it when they suspect too much or too little growth hormone (the pituitary gland's main growth signal), or when someone reports fatigue, muscle loss, or body-composition changes that basic labs do not explain.

The Endocrine Society's 2014 acromegaly guideline names IGF-1 the preferred first-line blood test for suspected growth hormone excess. That endorsement is why the test shows up in specialist workups rather than standard checkups. A clinician may also order it to set a baseline before growth-hormone-axis therapy. In that setting the point is comparison: one reading before, and follow-up readings later, so any change is measured against your own starting number rather than a population average.

What does an IGF-1 test measure

An IGF-1 test measures the amount of insulin-like growth factor 1 circulating in your blood. Your liver makes this hormone in response to growth hormone, so IGF-1 acts as a steady stand-in for a signal that is otherwise hard to catch.

Think of growth hormone as rain that falls in sudden bursts, and IGF-1 as the water level in a reservoir. The reservoir smooths out the bursts into one readable number. That is why a single IGF-1 draw is more informative than a single growth hormone reading. The test itself is straightforward: a routine blood draw, with no fasting required for most people. Results are always read against an age-adjusted reference range, because normal values shift with each decade. A number that looks high in isolation may be perfectly normal once your age is factored in.

When should you get an IGF-1 test

You should get an IGF-1 test when there is a specific question to answer, not as a default annual screen. Reasonable triggers include symptoms of a growth hormone disorder, a thorough midlife biomarker panel, or a pre-treatment evaluation.

Age matters when reading the result. Reference-interval data published in JCEM (2014) show the healthy upper limit for a young adult is far higher than for someone in their sixties. Pairing IGF-1 with related markers such as testosterone gives a clinician more context than any single number alone.

This article is educational and is not medical advice. Results vary based on individual factors. Halftime Health is launching soon — join the waitlist to get updates.