IGF-1 (Insulin-like Growth Factor 1)
A liver-derived hormone produced in response to growth hormone. Because GH is secreted in short pulses, IGF-1 is the stable proxy used to assess GH status.
The single marker for anyone running GH secretagogues. It's the only practical way to know whether ipamorelin, CJC-1295, sermorelin, tesamorelin or MK-677 are doing anything — and whether you've pushed into a range with real risk.
The plan of attack
In this order. Most people start at step four, which is why they change five things at once and learn nothing.
- Confirm the number is real
Age. Falls markedly with age, so an adult range spanning all ages is close to useless. Insist on an age-matched reference range. - Read it with its partner
If you run GH peptides without ever testing IGF-1, you're guessing. This is the objective readout. Draw it alongside: Fasting Insulin, HbA1c (Hemoglobin A1c), Free T4 (Thyroxine). - Work out which direction is yours
If it's high — Watch for fluid retention, carpal tunnel symptoms, joint pain, jaw/hand/foot growth, and worsening insulin sensitivity. Persistent elevation warrants stopping and reassessing.
If it's low — Poor recovery, reduced lean mass, poor sleep quality, low energy. Note IGF-1 falls in under-eating regardless of GH status. - Fix it in this order
Nutrition. IGF-1 is exquisitely protein- and energy-sensitive — it drops fast in caloric restriction and low protein intake. Adequate protein (0.7–1 g/lb) and energy are prerequisites before blaming the GH axis.
Lifestyle. Deep sleep is when the majority of GH is released — sleep quality is the biggest free lever. Resistance training and high-intensity work produce acute GH pulses.
Supplements. Nothing reliably raises IGF-1 beyond adequate nutrition. Arginine/ornithine claims are largely unsupported at oral doses. Address hypothyroidism and liver health.
Hormones. Exogenous GH raises IGF-1 potently but carries insulin resistance, edema, carpal tunnel and cost/legal considerations. Correct hypothyroidism first — it suppresses the GH axis.
Compounds. Baseline before starting; retest at 6–8 weeks. Ipamorelin/CJC-1295/sermorelin stimulate pulsatile GH; tesamorelin has the strongest human trial data (FDA-approved for HIV lipodystrophy, reduces visceral fat); MK-677 (ibutamoren) raises IGF-1 substantially but reliably worsens fasting glucose/insulin and causes water retention and appetite spikes — pair it with HbA1c and fasting insulin.
Work down the list, not across it. Adding a compound on top of an unfixed diet is why generic protocols fail. - Retest
Baseline, then 6–8 weeks after starting or changing dose; every 6 months on an ongoing protocol. Change one thing at a time, or the retest can't tell you which thing worked.
How to fix it
📚 Bidlingmaier M et al., J Clin Endocrinol Metab 2014 — age/sex-specific IGF-1 reference intervals. Falutz J et al., NEJM 2007 — tesamorelin RCT.
🩸 Test your IGF-1 (Insulin-like Growth Factor 1)
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Order this test — 10% off → Browse all 102 markers →What IGF-1 (Insulin-like Growth Factor 1) is usually tested alongside
On its own, one marker is a data point. These panels include IGF-1 (Insulin-like Growth Factor 1) plus the markers that make it interpretable — each names every test, why it is on the list, and loads the whole set into your cart in one click at 10% off.
includes this + 8 more markers — Using ipamorelin, CJC-1295, tesamorelin, sermorelin or MK-677 (ibutamoren).
includes this + 10 more markers — Taking or about to start semaglutide, tirzepatide or retatrutide — for weight, metabolic health, or both.
includes this + 7 more markers · built for women — Acne along the jawline, chin and neck that flares before your period, persisting or starting in your 20s, 30s or 40s.
What moves your IGF-1 (Insulin-like Growth Factor 1)
14 compounds in the Vault have a documented effect on this marker, or are a reason to have measured it first:
Browse all 237 compounds & 350 supplements →
Would you feel it? Symptoms IGF-1 (Insulin-like Growth Factor 1) helps explain
People rarely search for a marker — they search for how they feel. These are the complaints where this marker is worth checking, and whether it is a first-line test or a follow-up once the obvious causes are ruled out.
Why your IGF-1 (Insulin-like Growth Factor 1) might be wrong
Most abnormal results are interference, not disease. These are the things that measurably move this specific marker — check them before you change anything. Each one says whether the number is wrong and should be repeated, badly timed and should be redrawn, or real with a cause worth explaining.
Falls markedly with age, so an adult range spanning all ages is close to useless.
Insist on an age-matched reference range.
Under-eating produces hepatic GH resistance — GH goes up while IGF-1 falls. A low IGF-1 in a lean, hard-training person is usually under-fuelling, not deficiency.
Interpret against intake and training load.
IGF-1 is made in the liver, so impaired function lowers it regardless of GH.
Read alongside liver enzymes.
What IGF-1 (Insulin-like Growth Factor 1) means in combination
A single marker tells you a little. Combinations tell you the story — these are the named patterns this marker takes part in, and what each one points at.
Almost certainly nothing. GH is secreted in pulses during deep sleep and is undetectable between them, so a random draw catches a trough far more often than a peak. A single low GH is not evidence of deficiency.
IGF-1 is the stable proxy and it is the number to read. Genuine GH deficiency is diagnosed by stimulation testing, not a random level. If you are considering secretagogues, IGF-1 is the before-and-after marker.
Hepatic growth hormone resistance. The pituitary is shouting and the liver will not answer, because IGF-1 production requires adequate energy. This is the endocrine fingerprint of eating too little for your training load — not a growth hormone problem.
Eat more. No secretagogue overcomes this, because the missing input is calories rather than signal. See the RED-S and performance panels.
What to test next
Markers rarely answer alone. These are the ones that put IGF-1 (Insulin-like Growth Factor 1) in context — each with its own full breakdown.
Frequently asked questions
Strongly age-dependent: ~115–355 ng/mL at age 20–30, declining each decade. Always use the age-adjusted range on your report. Ranges vary by laboratory and assay — always compare to the range printed on your own report.
Upper-normal for your age — not above it. Supraphysiologic IGF-1 raises theoretical concerns for insulin resistance, tissue overgrowth and cancer-promoting signaling. More is explicitly not better.
Watch for fluid retention, carpal tunnel symptoms, joint pain, jaw/hand/foot growth, and worsening insulin sensitivity. Persistent elevation warrants stopping and reassessing.
Poor recovery, reduced lean mass, poor sleep quality, low energy. Note IGF-1 falls in under-eating regardless of GH status.
You can order IGF-1 (Insulin-like Growth Factor 1) directly through Marek Diagnostics without a doctor's visit — drawn at any Quest Diagnostics location in the US. Code CAMERON applies 10% off automatically.