Quick answer: the IGF-1 normal range depends on your age. Mayo Clinic Laboratories, using reference intervals from a 2014 multicenter study, lists 92.9 to 342.0 ng/mL at 21 to 25, 69.0 to 227.0 ng/mL at 36 to 40, 56.8 to 194.5 ng/mL at 46 to 50 and 38.3 to 162.5 ng/mL at 66 to 70. To convert ng/mL to nmol/L, multiply by 0.131. IGF-1 needs no fasting or special preparation (MedlinePlus).
IGF-1 normal range by age
Mayo Clinic Laboratories IGF-1 test catalog, based on Bidlingmaier et al, J Clin Endocrinol Metab 2014.
| Age | IGF-1 (ng/mL) | Approx. nmol/L |
|---|---|---|
| 18 | 120.5 to 485.8 | 15.8 to 63.6 |
| 20 | 107.8 to 416.0 | 14.1 to 54.5 |
| 21 to 25 | 92.9 to 342.0 | 12.2 to 44.8 |
| 26 to 30 | 78.4 to 270.0 | 10.3 to 35.4 |
| 31 to 35 | 73.1 to 243.0 | 9.6 to 31.8 |
| 36 to 40 | 69.0 to 227.0 | 9.0 to 29.7 |
| 41 to 45 | 61.5 to 204.4 | 8.1 to 26.8 |
| 46 to 50 | 56.8 to 194.5 | 7.4 to 25.5 |
| 51 to 55 | 53.0 to 189.6 | 6.9 to 24.8 |
| 56 to 60 | 45.6 to 172.4 | 6.0 to 22.6 |
| 61 to 65 | 42.2 to 169.0 | 5.5 to 22.1 |
| 66 to 70 | 38.3 to 162.5 | 5.0 to 21.3 |
| 71 to 75 | 36.6 to 164.7 | 4.8 to 21.6 |
ng/mL ranges from Mayo Clinic Laboratories; nmol/L is our conversion at 0.131. Assays differ, so other labs print different ranges: Oxford University Hospitals, for example, reports IGF-1 in nmol/L with its own age bands. Some labs also report a z-score or SDS, which places you against people your age; a z-score between minus 2 and plus 2 covers about 95% of healthy people of the same age.
What IGF-1 is
Insulin-like growth factor 1 is a hormone made mostly by the liver in response to growth hormone (GH). NIDDK explains that GH signals the liver to make IGF-1, and IGF-1 is what actually drives bone and tissue growth. GH is released in pulses through the day, so a single GH reading is rarely useful (MedlinePlus), while IGF-1 stays much steadier. That makes IGF-1 the standard way to check average GH activity. MedlinePlus notes levels are low in childhood, peak in puberty and decline through adulthood.
What high IGF-1 means
A high IGF-1 for your age may mean too much growth hormone: gigantism in children or acromegaly in adults, most often caused by a benign pituitary tumor (MedlinePlus; NIDDK). The Endocrine Society's acromegaly guideline recommends measuring IGF-1 in people with typical features such as enlarging hands and feet or coarsening facial features, and NIDDK says a high IGF-1 in most cases suggests acromegaly, with a glucose suppression test used to confirm. Taking growth hormone or GH-releasing products also raises IGF-1. A high result needs a doctor, not a retest at home.
What low IGF-1 means
MedlinePlus says a low IGF-1 in a child probably means GH deficiency or insensitivity, and in an adult may reflect normal age-related decline or another condition. Adults with true GH deficiency can have fatigue, lower bone density and less muscle, but MedlinePlus notes IGF-1 testing is not common for these symptoms because other disorders are much more likely causes.
Worked example
A 45-year-old gets an IGF-1 of 150 ng/mL (150 x 0.131 = 19.7 nmol/L). The Mayo range for 41 to 45 is 61.5 to 204.4, so 150 sits comfortably inside, a little above the middle. The same 150 ng/mL at age 22 would sit in the lower half of the 92.9 to 342.0 range, and at 70 it would be near the top of 38.3 to 162.5. That is why an IGF-1 without an age band means little.
A second 45-year-old taking a growth hormone product has 260 ng/mL, above the 204.4 upper limit for the age. The number reflects what is being taken, and it is a reason to review that with a doctor, since the guideline links persistently high IGF-1 with the health effects of GH excess.
Which test to use
| If you want | Test | Where |
|---|---|---|
| A baseline IGF-1 with a broad panel | IGF-1 add-on | SiPhox Longevity Essentials + ${money(PRICE.igf1)} |
| IGF-1 plus a full blood count | IGF-1 and CBC bundle | Any SiPhox EasyDraw panel + ${money(PRICE.cbcIgf1)} |
| To investigate suspected acromegaly | IGF-1 and an oral glucose suppression test | Endocrinologist |
| To investigate GH deficiency | GH stimulation testing | Endocrinologist |
Getting a reliable IGF-1 result
- No fasting needed. MedlinePlus says there is no special preparation, and IGF-1 is stable through the day.
- Use the same lab and assay. Ranges are method-specific; Mayo's are tied to one immunoassay and study.
- Compare with your age band. Always read the result against the band for your exact age, or use the z-score if the lab prints one.
- Record anything that affects GH. Growth hormone or GH-releasing products raise IGF-1, so note them when you compare tests.
Does SiPhox test IGF-1?
Yes, but only as an add-on. IGF-1 is not included on any of SiPhox's six base panels. SiPhox offers it as a per-test upgrade for +$70 on EasyDraw kits, or together with a complete blood count for +$100. So Longevity Essentials with IGF-1 costs $194 plus $25 shipping per test, and Ultimate 360 with IGF-1 costs $344 including shipping. Add-ons are chosen when you set up or change your membership.
| Base panel | Per test with shipping | With IGF-1 | With IGF-1 and CBC |
|---|---|---|---|
| Longevity Essentials | $149 | $219 | $249 |
| Hormone Focus | $149 | $219 | $249 |
| Ultimate 360 | $274 | $344 | $374 |
Our arithmetic from SiPhox's listed prices. SiPhox is a wellness service with no doctor review included, so an IGF-1 outside your age range goes to your doctor. See our SiPhox cost breakdown, biological age test guide and blood work for athletes.
A note on home samples: SiPhox's partner lab tests capillary blood collected from the upper arm. SiPhox says its results show a 95% to 99% correlation with venous draws in its own quarterly comparisons against Labcorp and Quest, but it has not published a study of the EasyDraw device. If a result would change a treatment decision, confirm it with a venous test through your doctor.
Longevity Essentials
The default panel: heart, metabolic, hormone and inflammation markers in one draw.
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Hormone Focus
Sex hormones for men and women, including PSA for men and progesterone for women.
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Ultimate 360
Everything on the four core panels plus iron studies, B12 and folate, GGT and PSA.
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Frequently asked questions
What is a normal IGF-1 level?
It depends on age. Mayo Clinic Laboratories lists 92.9 to 342.0 ng/mL at 21 to 25, 56.8 to 194.5 ng/mL at 46 to 50 and 38.3 to 162.5 ng/mL at 66 to 70.
What does high IGF-1 mean?
Too much growth hormone activity, from acromegaly (usually a pituitary tumor) or from taking GH or GH-releasing products. It needs a doctor's evaluation.
Do you need to fast for an IGF-1 test?
No. MedlinePlus says no special preparation is needed.
How do I convert IGF-1 from ng/mL to nmol/L?
Multiply ng/mL by 0.131. For example, 150 ng/mL is about 19.7 nmol/L.
Does SiPhox test IGF-1?
Only as an add-on: +$70 per test on EasyDraw panels, or +$100 with a CBC. It is not included on any base panel.
Sources
- Mayo Clinic Laboratories: Insulin-like growth factor 1, serum (reference values by age)
- Bidlingmaier M et al. Reference intervals for IGF-I from birth to senescence. J Clin Endocrinol Metab 2014
- MedlinePlus Lab Tests: IGF-1 (insulin-like growth factor 1) test
- MedlinePlus Lab Tests: Growth hormone tests
- NIDDK: Acromegaly
- Katznelson L et al. Acromegaly: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2014
- Oxford University Hospitals: IGF-1 test (nmol/L reference intervals)
- SiPhox Health: Longevity Essentials panel, marker list and per-cycle add-ons
- SiPhox Health: panel comparison (checked 29 Sep 2026)