IGF-1 levels by age generally fall after early adulthood. A number that fits a younger adult's range may be high for an older adult. But the range printed on your own lab report is the one that counts: different testing methods produce different results.
IGF-1 means insulin-like growth factor 1, a growth factor the liver makes in response to growth hormone, or GH. It gives a steadier picture of GH activity because GH comes in pulses. A lab result measures that activity. It doesn't measure how well someone is aging.
IGF-1 levels by age: an example reference chart
A reference range describes the spread found in a comparison population. It isn't a treatment goal.
Chanson and colleagues tested the same adult samples using six assays, meaning six laboratory testing methods. Their 2016 study in the Journal of Clinical Endocrinology & Metabolism showed substantial differences between methods. Below are selected age bands from Table 2's iSYS assay, in ng/mL, or nanograms per milliliter (the published dataset).
| Age in years | Male reference range, ng/mL | Female reference range, ng/mL |
|---|---|---|
| 18–20 | 168–391 | 155–421 |
| 30–39 | 108–265 | 113–294 |
| 40–49 | 91–233 | 97–253 |
| 50–59 | 81–214 | 80–209 |
| 60–69 | 75–208 | 64–170 |
| 70–89 | 64–192 | 56–154 |
These intervals cover the middle 95% of the modeled comparison distribution. They are examples from that study, not universal limits.
The same paper's IMMULITE method gave a male range of 118–348 at ages 30–39, compared with iSYS's 108–265. A chart without the testing method leaves out an essential part of the answer.
Sermorelin: the IGF-1 change in older adults
Sermorelin copies part of the body's signal to release GH. In Vitiello's 2006 Neurobiology of Aging trial, 100 healthy adults aged 60–85 entered; 89 completed six months. Among completers, IGF-1 rose 33.8% with sermorelin versus 0.8% with placebo, an inactive comparison injection (the full paper).
That wasn't a universal response. Vittone's 1997 study found no IGF-1 change in 11 older men after six weeks, despite increased overnight GH release. The sermorelin clinical trials page explains those different studies.
What a z-score adds to the lab result
A z-score shows how far a result sits from the typical level for that age and sex, in standard units. SDS, short for standard deviation score, means the same thing. Around zero is typical; positive values are above it and negative values below it.
As of October 1, 2026, the day this article was written, a laboratory reporting paper published September 3, 2026 described checks for adding these scores to IGF-1 reports. Its central point was that the calculation needs reference data matched to age, sex and testing method.
A score helps put a number in context. It still needs clinical interpretation, and it doesn't make results from every lab interchangeable.
What low IGF-1 means
A low result can raise a question about GH deficiency, meaning too little growth hormone. It doesn't answer that question alone.
Adults with that condition may have fatigue, reduced muscle mass or lower bone density, but those symptoms aren't specific to it (MedlinePlus's test explanation). Nutrition and illness can also affect the result.
The Endocrine Society guideline says diagnosis usually requires stimulation testing, which checks GH release after a controlled medical stimulus. Normal IGF-1 doesn't always rule out deficiency either. Age, symptoms and the rest of the medical history matter together.
Tesamorelin: an 81% rise in one trial
In Falutz's 2007 New England Journal of Medicine trial, 412 adults with HIV and excess abdominal fat received tesamorelin or placebo for 26 weeks. IGF-1 rose 81.0% with tesamorelin and fell 5.0% with placebo (the original report).
That describes a group average in a specific population. It doesn't establish an ideal rise, or what happens in someone without HIV. The tesamorelin clinical trials page covers the study's main question about deep abdominal fat.
What high IGF-1 means—and why monitoring matters
High IGF-1 can reflect a medicine's effect or excessive GH production. Acromegaly is a condition in which excess GH causes tissues to enlarge. A high result can prompt further testing; it doesn't diagnose acromegaly by itself (NIDDK's explanation).
The FDA's Egrifta WR label, marked “Revised: 3/2025,” says: “The effects of prolonged elevations in IGF-1 levels are unknown.” It calls for monitoring and tells prescribers to consider stopping treatment for persistent elevations, such as above 3 SDS, particularly without a robust treatment response.
In its 26-week trial data, about 47 in 100 treated participants exceeded 2 SDS; 36 in 100 exceeded 3 SDS. Those are findings from the studied Egrifta formulation, not rates established for compounded tesamorelin.
As of October 1, 2026, the day this article was written, the TRIUMPH protocol published July 8, 2026 planned IGF-1 checks at weeks 2, 12 and 24 during tesamorelin treatment. It included clinician-directed changes for elevated scores. A protocol is a study plan, not a report of results or a personal monitoring schedule.
CJC-1295: what “1.5- to 3-fold” means
Teichman's 2006 Journal of Clinical Endocrinology & Metabolism report studied a long-acting CJC-1295 molecule in healthy adults aged 21–61. After one injection, average IGF-1 reached 1.5 to 3 times its starting level for 9–11 days (the trial report).
A 1.5-fold level means 50% above the starting value. Threefold means 200% above it, rather than a 300% increase. Those are translations of the study's figures, not expected results for a prescription.
The tested molecule used DAC, a chemical attachment that makes it bind a blood protein and last longer. The trial didn't test CJC-1295 without that attachment or its combination with ipamorelin, another GH-release signal. Its figures cannot establish the blend's response.
The comparison that belongs in the visit
The useful comparison includes the result, its units, the lab's age-adjusted range, the testing method and earlier measurements. Your prescriber reads it against your lab's range. A higher result alone doesn't establish better sleep, strength or longer life; does sermorelin work explains that distinction.
Through Promise, these medicines are dispensed as compounded medications, prepared by a pharmacy for a prescription. That is different from an FDA-approved product: the formulations offered here are not FDA-approved. As of October 1, 2026, the day this article was written, the FDA explains that it doesn't verify compounded drugs' safety, effectiveness or quality before marketing.
A licensed provider may still prescribe a compounded formulation; that decision is between the patient and the doctor. At Promise, a licensed provider reviews every request, and not everyone qualifies.
