What is IGF-1? A plain-language definition
IGF-1 stands for insulin-like growth factor 1. It is a hormone, a chemical messenger in the blood that controls the actions of certain cells and organs. Its job is tied to growth hormone.
IGF-1
The single IGF-1 blood test, if a clinician has asked for IGF-1 specifically.
$129
See this test at HealthLabsPrice checked October 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.
What IGF-1 does
According to MedlinePlus, IGF-1 manages the effects of GH in your body, and the two promote normal growth of bones and tissues. GH also helps control metabolism, which is how the body turns food into energy.
Both hormones rise until they peak during puberty and fall once you are an adult. IGF-1 is also known as somatomedin C.
Why it is measured instead of GH
GH levels in the blood change through the day, depending on diet and activity. IGF-1 levels are more stable. That makes IGF-1 a reliable way to track GH in the body, which is why a provider may order it alongside GH tests (MedlinePlus, growth hormone tests).
What high and low levels can mean
Only a clinician can interpret a result, and labs use different ranges. In general, per MedlinePlus:
- High IGF-1 may mean gigantism in children or acromegaly in adults. Both are most often caused by a pituitary tumor.
- Low IGF-1 in a child suggests GH deficiency or insensitivity.
- Low IGF-1 in an adult may reflect normal age-related decline or another condition.
Is it a testosterone marker?
No. IGF-1 belongs to the growth hormone system. MedlinePlus says IGF-1 testing is not common in adults, because other disorders are much more likely to cause the symptoms of a GH disorder. Testosterone, free testosterone, LH and FSH answer different questions. The testosterone test guide explains which one to start with.
Where to go next
If you want to know who gets tested, how to prepare and how to order, read the IGF-1 test guide. If you have symptoms, see a clinician. A blood test you order yourself does not replace an exam.
IGF-1
$129
See this test at HealthLabsPrice checked October 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.
Keep reading
- IGF-1 test: what it measures, who needs one and how to order
An IGF-1 test tracks growth hormone activity, not testosterone. See who is usually tested, how to prepare and what a result can and can't tell you.
- SHBG test: when it helps and which order to place
An SHBG test shows how much testosterone is held by a binding protein. Learn when it helps, how to prepare and what a result can and can't tell you.