Key Takeaway
IGF-1 is the single best lab for tracking growth hormone peptide response. Normal adult ranges run 75 to 280 ng/mL depending on age. Anti-aging users target the 75th to 90th percentile for their age band. Retest at 6 to 8 weeks, then every 3 to 6 months.
If youre running sermorelin, CJC-1295, ipamorelin, tesamorelin, or MK-677, there is one lab you cant skip. Its IGF-1. Growth hormone itself is almost useless to measure because the pituitary releases it in sharp pulses, mostly while you sleep. By the time your blood hits the vial, the level has already dropped. IGF-1 is the steady downstream signal of that GH activity, and its what every serious clinician uses to tune a peptide protocol.
This guide covers the ranges by age, how to set a target, what rise to expect from each peptide, the cancer questions that keep coming up, and when to pull blood again.
Why IGF-1 matters more than GH itself
Growth hormone is pulsatile. Levels can swing from under 0.1 ng/mL to above 20 ng/mL within minutes. A random GH draw tells you almost nothing unless you catch a pulse, which is why clinical endocrinology uses stimulation tests instead. IGF-1, by contrast, is stable across the day and reflects integrated GH exposure over the last 12 to 24 hours.
Heres the mechanism. The pituitary releases GH. GH travels to the liver and binds GH receptors on hepatocytes. The liver then produces IGF-1 (insulin-like growth factor 1), which is what actually drives most of the downstream effects people credit to GH itself: tissue repair, lean mass retention, collagen synthesis, and the metabolic shifts users feel on peptide protocols.
If IGF-1 isnt moving, the peptide isnt working, or the dose is too low, or the injection technique is off. A good clinician treats IGF-1 like a T3/T4 on thyroid protocols. You titrate to a number, not a feeling.
Normal IGF-1 ranges by age
IGF-1 drops steadily with age. This is the pattern behind the anti-aging use of GH peptides: most adults over 40 sit in the lower third of the young-adult range, and peptide protocols aim to restore the midpoint or slightly above.
The ranges below are consensus reference intervals used by LabCorp, Quest, and most hospital assays. Individual labs publish slightly different numbers because they calibrate against different standards (the WHO 02/254 standard is the current reference).
| Age band | Normal IGF-1 (ng/mL) | Midpoint | Anti-aging target |
|---|---|---|---|
| 18 to 30 years | 100 to 280 | 190 | 220 to 260 |
| 30 to 50 years | 85 to 225 | 155 | 180 to 215 |
| 50 to 70 years | 75 to 200 | 140 | 160 to 195 |
| 70+ years | 55 to 160 | 108 | 130 to 155 |
A 45-year-old with an IGF-1 of 95 ng/mL is technically in range but sitting at the bottom 10th percentile for their age. Thats usually where peptide candidates land before they start. Pull a baseline before you order anything. See the complete lab panel before starting peptides for the rest of the workup.
How to set your IGF-1 target
The sensible target depends on why youre using GH peptides. Three common goals, three different numbers.
Check your GLP-1 eligibility
Use our free BMI Calculator to see if you may qualify for provider-reviewed GLP-1 therapy.
Try the BMI Calculator →Anti-aging and general healthspan. Aim for the 75th to 90th percentile of the normal range for your age, not above it. For a 45-year-old that means roughly 180 to 215 ng/mL. Youre restoring a youthful level, not chasing supra-physiology.
Post-surgical recovery or injury rehab. Short-term targets can run higher, up to the top of the age range, for 8 to 12 weeks. Drop back to the healthspan target after. This is where tesamorelin and CJC-1295 tend to be used clinically.
Documented adult GH deficiency. This is a medical diagnosis confirmed by stimulation testing, not a wellness goal. Targets are set by an endocrinologist and usually involve recombinant GH rather than peptides.
Most healthy biohackers shouldnt be pushing IGF-1 above the top of their age range. The risk-benefit curve bends the wrong way once you pass the upper reference limit, and the cancer-risk data (covered below) is clearer at that end. If your number is already at the 80th percentile, dont start a peptide.
Expected IGF-1 rise on each GH peptide
Different peptides produce different IGF-1 shifts. Secretagogues that mimic ghrelin (ipamorelin, MK-677) and analogues of GHRH (sermorelin, CJC-1295, tesamorelin) work through different receptors, which is why stacking a GHRH with a ghrelin mimetic produces synergy. Numbers below are averages from published trials and clinical practice; individual response varies by 30 to 50%.
| Peptide | Class | Expected IGF-1 rise | Time to plateau |
|---|---|---|---|
| Sermorelin | GHRH analogue | 20 to 40% | 3 to 6 months |
| CJC-1295 + ipamorelin | GHRH + ghrelin mimetic | 50 to 100% | 3 to 6 months |
| MK-677 (ibutamoren) | Oral ghrelin mimetic | 40 to 60% | 2 to 4 weeks |
| Tesamorelin | Stabilized GHRH | 15 to 25% | 8 to 12 weeks |
A user starting at IGF-1 of 120 ng/mL on CJC-1295 plus ipamorelin can reasonably expect to land at 180 to 240 ng/mL at the 6-month mark. If they dont, either the dose is too low, the product is underdosed, or absorption is poor. MK-677 is the fastest to show a signal because its oral, daily, and doesnt depend on pulsatile dosing. For full protocol context, read our peptide hub overview, and use the progress tracker to log labs over time.
Cancer risk concerns with high IGF-1
Epidemiology links high-normal and above-normal IGF-1 to higher rates of breast, prostate, and colorectal cancer. The EPIC cohort (Allen et al., Int J Cancer, 2010) found men in the top IGF-1 quintile had roughly 1.4x the prostate cancer risk of the bottom quintile. Similar signals show up for premenopausal breast cancer (Endogenous Hormones Breast Cancer Collaborative Group, Lancet Oncology, 2010) and colorectal adenomas.
Three caveats matter. First, most of these studies measured IGF-1 in untreated populations, not people on peptides, so direct extrapolation is imperfect. Second, the absolute risk increase is modest, roughly 20 to 40% relative, which on a low baseline is small. Third, IGF-1 is mechanistically linked to cancer cell proliferation through the IGF-1R receptor, so the biological plausibility is real even if the clinical numbers are soft.
Practical takeaway. Dont push IGF-1 above the upper limit of your age-adjusted reference range. If you have a personal or strong family history of hormone-sensitive cancer (breast, prostate, colorectal), GH peptides arent a good fit. A consult through FormBlends or a provider on the directory can help you weigh the tradeoff honestly.
When and how to retest IGF-1
Baseline, then 6 to 8 weeks after starting the peptide, then every 3 to 6 months on therapy. Thats the standard cadence. Retest sooner if you change dose, switch peptide, or add a second compound. Fasting isnt required but morning draws are preferred because they standardize the time-since-last-meal variable.
Order IGF-1 plus IGFBP-3 (the main binding protein) together if your lab offers it. The IGF-1 to IGFBP-3 molar ratio, typically 0.1 to 0.2, gives a better picture of free, bioactive IGF-1 than IGF-1 alone. Assay method matters too. LC-MS/MS is the most accurate and reproducible. IRMA and RIA are older immunoassays and can vary between labs; if youre tracking trends, use the same lab each time.
If your IGF-1 drops below baseline or stays flat after 8 weeks on therapy, something is wrong. Check the product (pharmacy compounding quality, storage temperature), the injection site rotation, the timing (GHRH peptides work best at bedtime on an empty stomach), and your sleep. Poor sleep blunts GH pulses and caps IGF-1 regardless of dose.
Frequently asked questions
Do I need to fast for an IGF-1 test?
No, IGF-1 is stable across the day and doesnt move much with meals. Morning draws are still preferred because most reference ranges were built on morning samples, and it keeps your tracking consistent over time.
How much does an IGF-1 test cost without insurance?
Direct-to-consumer IGF-1 tests run $45 to $95 through services like LabCorp OnDemand, Quest, or Ulta Labs. Adding IGFBP-3 adds another $35 to $60. Total panel cost for IGF-1 plus IGFBP-3 should stay under $150 cash pay.
Can I test IGF-1 at home with a finger stick?
Not reliably. Current finger-stick assays for IGF-1 are limited and most biohackers use venous draws. A few at-home kits (Everlywell, Thorne) offer dried blood spot IGF-1 testing, but the correlation with venous serum is only moderate. Use venous draws when possible.
What if my IGF-1 is already high before starting peptides?
If baseline IGF-1 is above the age-adjusted upper limit, dont start a GH peptide without an endocrinology workup. Elevated baseline can point to acromegaly, a pituitary adenoma, or rarely a GH-secreting tumor. Rule those out first. A high-normal baseline also means the peptide has less upside and more risk.
Does IGF-1 respond to diet and exercise alone?
Yes, to a degree. Resistance training, adequate protein, deep sleep, and sufficient calories all support IGF-1. Severe caloric restriction, low protein intake, and chronic sleep deprivation drop it. Fix those variables before spending money on peptides. Many low-IGF-1 results in people over 40 are lifestyle issues, not hormone issues.
How long after stopping a peptide does IGF-1 return to baseline?
2 to 6 weeks for most peptides. Sermorelin and ipamorelin clear fast, so IGF-1 drops within 2 to 3 weeks of stopping. CJC-1295 with DAC (the long-acting version) can sustain IGF-1 for 4 to 6 weeks after the last dose. MK-677 drops within 1 to 2 weeks given its short receptor half-life relative to cumulative effect.
Should I also test growth hormone directly?
Not usually. Random GH is almost meaningless because of pulsatility. If your clinician wants to evaluate the GH axis directly, theyll order a stimulation test (glucagon, arginine, or macimorelin), not a random GH. For peptide tracking, IGF-1 is what you want. See the peptide hub for related protocol guidance.
Does high IGF-1 always mean cancer risk?
No. High IGF-1 is a population-level risk marker, not an individual diagnosis. Someone at the 80th percentile for their age isnt meaningfully different from someone at the 60th percentile. The concern grows above the upper reference limit and for people with existing cancer risk factors. Keep IGF-1 inside the age-adjusted normal range and the signal is weak.
Medical disclaimer: This article is for educational purposes only and is not medical advice. Always consult your healthcare provider before starting any medication. Individual results vary. FormBlends is a licensed telehealth platform; nothing here replaces a personal clinical evaluation.
Last reviewed: 2026-04-17