IGF-1 test: what it measures, who needs one and how to order

An IGF-1 test measures insulin-like growth factor 1 in your blood. It is a growth hormone marker, not a testosterone test. If your question is whether your testosterone is low, this is not the test to start with.

This page is for buying and preparing. If you only want the definition, read what IGF-1 is.

IGF-1

A single IGF-1 test, for when IGF-1 is the one marker you or your clinician want checked and a full panel is more than you need.

$129

See this test at HealthLabs

Price checked October 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.

What the test measures

IGF-1 is a hormone that manages the effects of growth hormone in the body. GH levels in the blood swing through the day. IGF-1 levels are steadier, so measuring IGF-1 is a more reliable way to track GH than measuring GH itself (MedlinePlus). The test is also called somatomedin C.

Who might consider it

MedlinePlus describes two main groups. Children with signs of a GH disorder, such as slowed growth, are the usual case. In adults, the test is uncommon because other conditions are much more likely to cause the same symptoms. Adults who may be tested include those with signs of too much GH, such as a deep, husky voice or thickened bones, and those being monitored during treatment for a GH disorder.

MedlinePlus lists fatigue as a possible symptom of GH deficiency in adults, but says IGF-1 testing isn’t common for adults because other disorders are much more likely to cause it. Low sex drive isn’t on its list. The Endocrine Society’s guideline for men with suspected low testosterone centers on testosterone itself, and on LH and FSH to find where a problem sits (Bhasin et al., 2018). If that is your question, see the testosterone test guide, the LH and FSH guide and the test finder.

Which order to place

If IGF-1 is the one marker you need, the single test is the smaller order. The seller also includes IGF-1 inside some of its larger male hormone panels, together with many unrelated tests. Those panels make sense only if you need the other tests as well. See male hormone panels compared before paying for a bundle.

How to prepare

MedlinePlus says you don’t need any special preparation for an IGF-1 test. The seller’s page for this test doesn’t state a fasting rule. Follow the instructions on your lab order, and tell the person drawing your blood about any medicines and supplements you take. Don’t stop a prescribed medicine unless your clinician says to.

The test is a blood draw from a vein in the arm, which usually takes under five minutes.

What a result can and can’t tell you

MedlinePlus gives no reference range for IGF-1, and labs set their own. Levels change with age: GH and IGF-1 rise to a peak in puberty and fall in adulthood. Use the range printed on your report, not a number from a web page.

• High: may point to gigantism in children or acromegaly in adults, most often caused by a pituitary tumor. If no tumor is found, more testing is needed to find the cause.
• Low in an adult: may be normal age-related decline or another condition, and further tests may be needed.

What it can’t do: diagnose a GH disorder by itself. MedlinePlus lists GH stimulation and suppression tests and IGFBP-3 as possible next steps. An abnormal IGF-1 result is a reason to see a clinician. A normal one does not rule out every cause of your symptoms.