IGF-1 (Insulin-like Growth Factor 1): what your level actually means
Also known as: Insulin-like Growth Factor 1, Somatomedin C · Updated 19 Aug 2026 · Educational — not medical advice
The short answer: IGF-1 is a hormone produced mainly in the liver in response to growth hormone, and its normal range shifts substantially with age, roughly 100 to 300 ng/mL is a common adult reference band, but children, teenagers, and older adults have meaningfully different expected values. Because of this age dependence, an IGF-1 result is only truly meaningful when interpreted against the range for your specific age group.
Where does your value sit?
This IGF-1 (Insulin-like Growth Factor 1) value is inside the normal range. Your lab's printed reference range takes precedence — ranges vary slightly between laboratories.
What IGF-1 tells you
IGF-1 acts as a stable, easy-to-measure stand-in for growth hormone, which itself is released in short pulses that are hard to capture with a single blood draw. Levels naturally rise through childhood, peak around puberty, and gradually decline with age, so labs typically report results against age-specific reference ranges rather than one fixed adult range. (Illustration is schematic.)
Common reasons it rises
- Acromegaly or gigantism — growth hormone-secreting pituitary tumors are the classic cause of a persistently high IGF-1.
- Recent intense exercise or certain supplements — can transiently raise levels in some people.
- Obesity in some cases — can be associated with altered IGF-1 levels depending on other metabolic factors.
And reasons it runs low
- Growth hormone deficiency — whether from childhood onset or an adult pituitary problem, this is a leading cause of low IGF-1.
- Malnutrition or chronic illness — poor nutrition and long-term illness can lower IGF-1 independent of growth hormone levels.
- Liver disease — since IGF-1 is produced mainly in the liver, significant liver dysfunction can lower levels.
- Normal aging — IGF-1 naturally declines with age, so a lower value in an older adult may simply reflect this expected pattern.
Does food or exercise change this?
Check with your doctor first: A significantly high or low IGF-1, especially with changes in hand, foot, or facial size or unexplained fatigue, should be evaluated by a doctor rather than managed through diet.
General guidance for adults — not a personal diet plan. Your doctor or dietitian knows your full picture.
Checked against: IGF-1 Test — MedlinePlus · Acromegaly — Mayo Clinic
What to do next
Ask your doctor: “Is this result being compared against the correct reference range for my age?”
Ask your doctor: “Could this reflect a growth hormone problem, or is it more likely explained by nutrition, liver health, or age?”
Ask your doctor: “Would further pituitary testing be useful given this result?”
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Questions people ask
Why does IGF-1 change so much with age?
Growth hormone and IGF-1 naturally rise sharply through childhood, peak during puberty's growth spurt, and then decline gradually through adulthood as the body's growth needs decrease. This is a normal biological pattern, which is why labs use age-specific reference ranges rather than one number for everyone.
Can lifestyle factors affect my IGF-1 level?
Yes, nutrition status has a notable effect — both malnutrition and, in some cases, obesity can shift IGF-1 away from what would be expected for someone's age. Because of this, doctors consider overall health and body composition alongside the number itself rather than reading it in isolation.
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