HGH Levels by Age: What’s Normal and What’s Not (Chart)

You came here for a chart. I’m going to give you one — but not the one you searched for, and it’s worth thirty seconds to explain why.

A “normal HGH level by age” chart is close to meaningless. Growth hormone is released in bursts, and between those bursts it’s often undetectable in a healthy man. A single blood draw catches you at a random point in that cycle.

What you can measure reliably is IGF-1. That’s the chart below, with the numbers your lab actually uses.

Why There’s No Useful “HGH Level” Chart

This is the part almost every page on this topic skips, and it changes how you should read your results.

Growth hormone isn’t released steadily. Your pituitary fires it in pulses — a large one shortly after you fall asleep, then smaller ones through the day.

Between those pulses, circulating GH drops to very low levels. In healthy men, a random daytime sample frequently comes back undetectable.

What that means in practice

Draw blood during a pulse and your GH looks high. Draw it twenty minutes later and it looks like zero.

Neither number tells you anything about your actual daily output. It tells you what time it was when the needle went in.

This is why endocrinologists don’t diagnose growth hormone deficiency from a random GH test. They use stimulation testing — provoking a GH response with insulin, glucagon or macimorelin and measuring whether the pituitary can deliver.

So if you see a chart listing “normal HGH: 0.4–10 ng/mL for men aged 40–49,” treat it with suspicion. Those numbers exist, but they describe a snapshot of a moving target.

The one exception

There is a situation where a GH test is genuinely useful, and it runs in the opposite direction.

If acromegaly is suspected — GH excess from a pituitary tumor — the test is an oral glucose tolerance test. You drink 75g of glucose, which should suppress GH in a healthy person. Failure to suppress is diagnostic.

That’s a provocation test too. Still not a random draw.

What to Measure Instead: IGF-1

Growth hormone signals your liver to produce IGF-1, and IGF-1 behaves completely differently in the bloodstream.

It has a long half-life and stays stable through the day. That means a single sample reflects your integrated GH output over roughly 24 hours, rather than one moment.

That’s why IGF-1 is the standard screening marker for the GH axis — and why it’s the number worth charting.

Practical notes for testing:

• Fasting isn’t required
• A morning draw improves reproducibility
• Use the same lab each time (more on why below)

IGF-1 Levels by Age: The Chart

Approximate adult reference intervals in ng/mL, as used by major US laboratories. These represent roughly the 2.5th to 97.5th percentiles of a healthy population.

Age	Typical range	Where that sits 0200400600800	What it means
17–24	180 – 780ng/mL	width 600 — the widest spread of any bracket	Peak adult output. A huge ceiling, and enormous variation between healthy individuals.
25–39	114 – 400ng/mL	width 286 — the ceiling has already halved	The decline has started, and it’s the ceiling that falls first — the floor barely moves.
40–54	90 – 360ng/mL	width 270	Where most men reading this will land. 150 ng/mL here is unremarkable — the same number at 22 would not be.
55+	70 – 290ng/mL	width 220	Lower floor, lower ceiling. This is normal ageing, not a disease.
70+	50 – 190ng/mL	width 140 — under a quarter of the youngest bracket	Some labs quote intervals this low for the oldest brackets. Check yours.

Look at the bars, not just the numbers. The range doesn’t only slide downward — it compresses, from a 600-point spread at 20 to about 140 by 70. Which is why the age bracket matters more than the value: 150 ng/mL sits comfortably mid-range at 45 and well below the 10th percentile at 22.

And read it against your own lab’s interval, not this one. Comparisons of commercial IGF-1 immunoassays have found between-laboratory variation of roughly 19–26%, with individual sample comparisons ranging as high as 36%. The practical consequence is blunter than the percentages suggest: the same sample can read normal on one platform and abnormal on another. Ranges verified August 2026.

During puberty, values commonly exceed 400 ng/mL and can run past 600 — entirely physiologic and not relevant to adult interpretation.

How to read this properly

Compare against the age bracket printed on your own report, not the one you feel closest to.

This is the single most common mistake. A 55-year-old with an IGF-1 of 95 ng/mL is within normal limits. The identical number in a 25-year-old would sit well below the 10th percentile and warrant investigation.

The number means nothing without the age. That’s the whole point of the chart.

A note on sex differences

Age effects dominate, but sex matters at the margins. Premenopausal women tend to run roughly 10–15% lower than age-matched men.

One clinically useful detail: oral estrogen suppresses IGF-1 production in the liver. A woman on oral contraceptives or oral HRT may show a low IGF-1 that doesn’t reflect her actual GH status. Transdermal estrogen doesn’t have this effect.

Where Does Your Result Sit?

🧮 Where Does Your IGF-1 Sit?

Enter your age and result to see where you fall within your own age bracket

Your age Adults 17 and over

Your IGF-1 In ng/mL

See where I sit

Read this before you act on it. This tool uses approximate reference intervals from major US laboratories and assumes those intervals span the 2.5th to 97.5th percentiles. Comparisons of commercial IGF-1 immunoassays have found between-laboratory variation of roughly 19–26%, with individual sample comparisons as high as 36% — meaning the same sample can read normal on one platform and abnormal on another. The interval printed on your own lab report always takes precedence over this. It is an orientation tool, not a diagnosis, and no result here is a reason to start or stop any treatment.

The Catch: Labs Don’t Agree With Each Other

Here’s the finding that should change how you use any IGF-1 chart, including mine.

IGF-1 immunoassays are not standardized. A 2019 international consensus on assay harmonization found inter-assay coefficients of variation as high as 30% across six commercial platforms.

Read that again. The same blood sample, run on different manufacturers’ equipment, can produce results that differ by up to a third.

What follows from that

Don’t compare a Quest result to a Labcorp result. The absolute numbers may not be measuring on the same scale.

Always use your own lab’s printed reference range, because that range is matched to their assay.

Track trends within one lab, not across several. If you’re monitoring change over time, the consistency of the platform matters more than the absolute value.

And be sceptical of any single chart presented as universal — including this one. It’s a reasonable orientation. It isn’t a substitute for the range on your report.

How Fast Does It Actually Decline?

The common figure is about 14% per decade after age 30. That’s a reasonable average, but it hides something more useful.

The decline isn’t a smooth line. It’s front-loaded.

A study tracking 149 healthy men aged 16 to 83 found two distinct phases. Between early adulthood and midlife, GH secretion fell by roughly 372 micrograms per decade. From midlife into old age, the further decline was only about 43 micrograms per decade.

Most of what you lose, you lose before 50.

That decline also tracked something specific: the collapse of deep slow-wave sleep, which fell from about 19% of the night in the youngest group to 3.4% by the late forties.

If you want the full picture of what drives that decline and what can be done about it, we cover it in detail in our guide to HGH and aging.

What Counts as “Low”?

Careful here, because this is where a lot of men get sold something.

Below the age-adjusted range on your own lab report is worth investigating.

Below a young adult’s range but within your own age bracket is normal. This is the trick anti-aging clinics use — compare a 50-year-old’s IGF-1 to a 25-year-old’s reference interval, declare a deficiency, and offer treatment.

By that logic every man over 40 is deficient, which means the word has stopped doing any work.

A low result usually isn’t a pituitary problem

Worth knowing before you spend money on further testing.

In someone without known pituitary disease, a low IGF-1 on its own is not particularly diagnostic. Confirming actual growth hormone deficiency requires stimulation testing.

And in practice, most low-normal IGF-1 results in middle-aged men have more mundane explanations:

• Excess visceral fat, which directly suppresses GH secretion
• Poor sleep or untreated sleep apnea — most GH output happens during early sleep
• Under-eating protein or chronic energy restriction, since IGF-1 is nutritionally sensitive
• Fasting, which suppresses IGF-1 even while raising GH — so don’t test during an aggressive fasting phase
• Poorly controlled diabetes, liver disease, or hypothyroidism

That fourth point catches people out. If you’re running 16:8 or doing regular 24-hour fasts, test in a fed state, or you’ll be measuring the fast rather than your baseline.

Legal View

Here’s what you need to know before you even think of HGH therapy:

What the Clinics Won’t Tell You

Search this topic and most of what you’ll find is published by companies that sell growth hormone therapy. Their charts are real. What surrounds those charts is a sales process.

One states plainly that if you’re diagnosed with growth hormone deficiency, “the safest and most effective treatment is prescription growth hormone injections.”

Two things are missing from that sentence.

The evidence doesn’t support it

A systematic review in Annals of Internal Medicine pooled 18 randomized controlled trials of growth hormone in healthy older adults.

The finding: small changes in body composition, and significantly increased rates of adverse events — soft tissue swelling, joint pain, carpal tunnel syndrome, gynecomastia, and higher rates of impaired fasting glucose and diabetes.

The conclusion was that growth hormone cannot be recommended as an anti-aging therapy.

That’s not a fringe position. It’s the pooled result of every controlled trial available at the time.

And the legal position is stricter than most people realize

In the United States, distributing human growth hormone for anti-aging, athletic or performance purposes — as opposed to a recognized medical condition — is a federal offense under 21 U.S.C. § 333(e), carrying up to five years’ imprisonment.

The FDA has taken the position that writing a prescription for an unauthorized use constitutes distribution under that statute. Anti-aging clinic operators have been federally prosecuted on exactly this basis, and a few states go further and criminalize possession.

Prescription somatropin is legitimate medicine for a narrow set of conditions: pituitary disease, Turner and Prader-Willi syndromes, short bowel syndrome, HIV-associated wasting.

Feeling tired at 52 with an IGF-1 of 130 ng/mL is not on that list.

How to spot the pitch

The pattern is consistent enough to recognize.

Step one: your IGF-1 is compared to a young adult reference interval rather than your own age bracket.

Step two: the resulting gap is described as a deficiency.

Step three: treatment is offered.

By that logic, essentially every man over 40 is deficient — which is another way of saying the word has stopped meaning anything.

If a page shows you a chart and the next thing it shows you is a consultation booking form, read the chart and ignore the form.

Where that leaves you

If you have a genuine clinical reason to suspect deficiency — pituitary tumor, head trauma, cranial radiation — see an endocrinologist. That pathway is real, and stimulation testing exists for exactly this purpose.

For everyone else, a low-normal IGF-1 in middle age is far more often explained by visceral fat, poor sleep or insulin resistance than by a pituitary problem. Those are cheaper to fix and considerably safer to address.

What to Actually Order

If you’re going to spend money on bloods, order the panel rather than the single marker. IGF-1 in isolation explains less than you’d think.

The core test:

• IGF-1, interpreted against age-adjusted ranges

Order alongside it:

• Total and free testosterone, plus SHBG — symptoms overlap almost completely
• Full thyroid panel — TSH, free T4, free T3
• Fasting insulin and HbA1c — these often explain the IGF-1 result
• Comprehensive metabolic panel — liver function affects IGF-1 production directly
• Vitamin D, ferritin, B12

If your fasting insulin is elevated and your IGF-1 is low, you probably don’t have a pituitary problem. You have a metabolic one — which is better news, because it responds to what you do.

See an endocrinologist if you have a history of pituitary tumor, head trauma or cranial radiation, or if IGF-1 sits well below your age-adjusted range on repeat testing.

What Moves the Number

Briefly, because it’s the obvious next question.

Sleep does more than anything else. Roughly 70% of daily GH output happens during early sleep, and deep sleep collapse is what tracks the age-related decline most closely.

Visceral fat loss. Belly fat directly suppresses GH secretion, and the effect is largely reversible with weight loss.

Training intensity. Sprint intervals and short-rest resistance work produce the largest acute responses.

Adequate protein. IGF-1 is nutritionally sensitive — chronic under-eating suppresses it regardless of what your GH pulses are doing.

Realistic timeline: expect three to six months before lab values reflect lifestyle changes. Retesting at four weeks measures noise.

If you’ve got sleep, body fat and training handled and want to know whether supplemental support is worth the money, our breakdown of the best legal HGH alternatives covers which formulas disclose their doses honestly and which are selling a story.

Frequently Asked Questions

What is a normal HGH level by age?

There isn’t a useful one. Growth hormone is released in pulses and is often undetectable between them, so a random blood draw reflects the timing of the test rather than your output. IGF-1 is the marker with meaningful age-adjusted ranges.

What is a normal IGF-1 level for my age?

Approximately 180–780 ng/mL at 17–24, 114–400 at 25–39, 90–360 at 40–54, and 70–290 above 55. Always read your result against the range printed on your own lab report, since assays vary.

Why do different labs give different IGF-1 results?

IGF-1 immunoassays aren’t standardized. A 2019 international consensus found inter-assay variation of up to 30% across six commercial platforms, so results aren’t directly comparable between labs.

Is my IGF-1 low if it’s below a young adult’s range?

No. Declining IGF-1 with age is normal. Low means below the range for your age bracket — and clinics that compare middle-aged men to a 25-year-old’s range are manufacturing a diagnosis.

Should I fast before an IGF-1 test?

Fasting isn’t required, and it’s actually counterproductive. Fasting suppresses IGF-1 while raising GH, so testing during a fasting phase measures the fast rather than your baseline. A morning draw in a fed state is more reproducible.

How often should I retest?

Every three to six months if you’re tracking change. Anything sooner mostly measures assay variability and day-to-day noise.

The Bottom Line

The chart you searched for doesn’t really exist, and the reason matters: growth hormone is pulsatile, so a single measurement tells you what time it was rather than what your output is.

IGF-1 is the number that works — roughly 180–780 ng/mL in your late teens and twenties, falling to 114–400 by your thirties, 90–360 through your forties and early fifties, and 70–290 beyond that.

But read it against your own lab’s range, because assays vary by as much as 30% between platforms and the absolute numbers aren’t portable.

Two things worth remembering. Below a young adult’s range is not the same as low — that conflation is the entire business model of the anti-aging clinic industry. And a low result in a middle-aged man is far more often about visceral fat, sleep or insulin than about his pituitary.

Test the whole panel, test fed rather than fasted, use the same lab twice, and give it three to six months before you judge whether anything changed.

This article is for informational purposes and is not medical advice. Reference ranges vary between laboratories and assays. Discuss any abnormal result with a physician, and do not begin hormone therapy on the basis of a single blood test.

References

IGF-1 reference ranges and interpretation

1. Labcorp. Insulin-like Growth Factor 1 (IGF-1), test 500485 — age-specific reference intervals. — https://specialtytesting.labcorp.com/tests/500485/insulin-like-growth-factor-1-igf-1
2. Mayo Clinic Laboratories. Insulin-Like Growth Factor 1, Serum (IGF1S) — reference intervals derived from Bidlingmaier M, Friedrich N, Emeny RT, et al. Reference intervals for insulin-like growth factor-1 (IGF-1) from birth to senescence. J Clin Endocrinol Metab. 2014;99(5):1712–1721. — https://www.testcatalog.org/show/IGF1S
3. HealthRX. IGF-1: how to interpret your result. — https://healthrx.com/labs-igf-1/how-to-interpret

Assay variability between laboratories

4. Massart C, Poirier JY. Variability among five different commercial IGF-1 immunoassays in conditions of childhood-onset GH deficiency and GH therapy. — https://pubmed.ncbi.nlm.nih.gov/17323843/
5. Discordance of insulin-like growth factor-1 results and interpretation on four different platforms. Clin Chim Acta. 2022. — https://www.sciencedirect.com/science/article/abs/pii/S0009898122014012
6. IGF-I assay methods and biologic variability: evaluation of acromegaly treatment response. Eur J Endocrinol. 2024;191(1):R1. — https://academic.oup.com/ejendo/article/191/1/R1/7698331

GH pulsatility and testing

7. Van Cauter E, Plat L. Physiology of growth hormone secretion during sleep. J Pediatr. 1996;128(5 Pt 2):S32–7. — https://www.jpeds.com/article/S0022-3476(96)70008-2/fulltext
8. Growth Hormone and Aging. Endotext, NCBI Bookshelf. — https://www.ncbi.nlm.nih.gov/books/NBK279163/

Age-related decline

9. Van Cauter E, Leproult R, Plat L. Age-related changes in slow wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men. JAMA. 2000;284(7):861–868. — https://pubmed.ncbi.nlm.nih.gov/10938176/
10. Toogood AA, O’Neill PA, Shalet SM. Beyond the somatopause: growth hormone deficiency in adults over the age of 60 years. J Clin Endocrinol Metab. 1996;81(2):460–465. — https://academic.oup.com/jcem/article/81/2/460/2649335

Body fat and IGF-1 suppression

11. Rasmussen MH. Obesity, growth hormone and weight loss. Mol Cell Endocrinol. 2010. — https://www.sciencedirect.com/science/article/abs/pii/S0303720709004377

Evidence for GH in healthy older adults

12. Liu H, Bravata DM, Olkin I, et al. Systematic review: the safety and efficacy of growth hormone in the healthy elderly. Ann Intern Med. 2007;146(2):104–115. — https://pubmed.ncbi.nlm.nih.gov/17227934/

Legal status

U.S. DOJ. Owner and operator of anti-aging center sentenced for distributing growth hormones. — https://justice.gov/usao-wdla/pr/owner-and-operator-anti-aging-center-sentenced-distributing-growth-hormones

21 U.S. Code § 333 — Penalties. Cornell Legal Information Institute. — https://www.law.cornell.edu/uscode/text/21/333