Normal IGF-1 Levels by Age: What the Numbers Mean

Normal IGF-1 levels by age usually fall between roughly 50 and 500 ng/mL, with the highest values during puberty and a gradual decline that begins in the 20s. Because every laboratory sets its own reference interval, a result is only normal or abnormal compared with the range printed on that specific report. IGF-1 (insulin-like growth factor 1) is a hormone produced mostly in the liver in response to growth hormone, so the number is a rough snapshot of how much growth hormone the body has been making.

What IGF-1 Measures and Why Age Matters

Growth hormone is released in pulses, which makes it hard to measure directly. IGF-1 stays fairly stable through the day, so doctors use it as a steadier proxy for growth hormone activity.

IGF-1 rises sharply during childhood and puberty, then falls steadily with age. A level of 300 ng/mL can be perfectly normal for a 16-year-old and above the expected range for someone in their 70s.

Clinicians order IGF-1 to screen for growth hormone deficiency, to monitor growth hormone replacement, and to check for excess growth hormone production such as acromegaly in adults or gigantism in children.

Typical IGF-1 Reference Ranges by Age

The table below shows approximate ranges reported by major US laboratories, given in both ng/mL and nmol/L. Treat it as a general guide, not a substitute for your own lab's reference interval.

Age group	Typical IGF-1 (ng/mL)	Typical IGF-1 (nmol/L)	Notes
0-5 years	40-250	5-33	Very wide variation
6-8 years	50-300	7-39	Slow, steady climb
9-11 years	90-350	12-45	Puberty begins
12-14 years	150-500	20-65	Common peak window
15-18 years	200-500	26-65	Still elevated
19-24 years	180-400	23-52	Starts to level off
25-39 years	120-350	16-45	Gradual decline
40-54 years	90-280	12-36	Age-adjusted drop
55-69 years	70-250	9-32	Lower baseline
70+ years	50-200	7-26	Lowest typical range

To convert nmol/L to ng/mL, multiply by about 7.7. Pediatric ranges are especially broad because children of the same age can be at very different stages of pubertal development.

IGF-1 Levels in Children and Teens

Parents searching normal igf 1 levels by age 8 and normal igf-1 levels by age 14 are usually asking the same thing: is my child's number in the right place for their stage of growth? Age alone is a rough guide.

Pediatric endocrinologists typically compare IGF-1 against bone age and Tanner stage rather than a birthday. Two 12-year-olds can have very different results, and both can be normal.

• Ages 8-10: often 50-300 ng/mL, with heavy overlap between children.
• Ages 11-14: values climb quickly, commonly 150-500 ng/mL at peak puberty.
• Below-range levels in a short child may prompt growth hormone stimulation testing.
• Above-range levels with unusually fast growth need evaluation for excess growth hormone.

Normal IGF-1 Levels in Adults

Normal igf 1 levels in adults typically sit somewhere between 90 and 350 ng/mL depending on age, with a slow decline after the mid-20s. Many labs also report a standard deviation score (SDS or Z-score) because that adjusts for age more precisely than a plain range.

Persistently low IGF-1 in an adult can point to growth hormone deficiency, but it can also reflect malnutrition, hypothyroidism, liver disease, poorly controlled diabetes, or a recent illness. A single low value is rarely enough to make a diagnosis.

Do Men and Women Have Different IGF-1 Ranges?

Most charts of igf-1 levels by age and gender do not split adult ranges by sex, because the overlap between men and women is large. Average values in women are sometimes slightly lower, and estrogen-containing birth control can lower IGF-1 further by changing how the liver responds to growth hormone.

Pregnancy raises IGF-1, sometimes above the non-pregnant range. For routine evaluations, age is a far bigger factor than gender.

How to Read Your IGF-1 Test Results Range

• Check the units. ng/mL and nmol/L are not interchangeable, and unit mix-ups are a common source of confusion.
• Check the age-matched range. A fitness influencer's number or an online chart for a different decade tells you nothing about your own result.
• Look at the Z-score. A Z-score of 0 is average; beyond roughly +2 or -2 is usually flagged.
• Consider context. Recent illness, fasting state, medications, and body weight can all shift the reading.
• Repeat borderline results. Doctors often recheck before labeling anything abnormal.

What Can Raise or Lower IGF-1

People who search how to increase igf-1 are usually asking about natural levers. The honest answer is that genetics, age, and growth hormone status dominate, and lifestyle moves the needle only modestly.

• Can raise it: adequate protein intake, sufficient sleep, resistance training, correcting hypothyroidism, and prescribed growth hormone therapy.
• Can lower it: under-eating or crash dieting, chronic illness, liver disease, uncontrolled diabetes, high-dose corticosteroids, and oral estrogen.
• Unproven: most over-the-counter "IGF-1 booster" supplements have little reliable evidence behind them.

Hormone topics often overlap. People researching growth hormone frequently also ask does hgh affect testosterone levels, and the short answer is that growth hormone therapy is not a dependable way to raise testosterone.

When a Result Falls Outside the Normal Range

A high IGF-1 in an adult may suggest acromegaly, while a high value in a child may suggest gigantism; both warrant an endocrinology workup. Pregnancy, puberty, and injected growth hormone are common benign explanations for an elevated result.

Low IGF-1 can reflect growth hormone deficiency, but also poor nutrition, hypothyroidism, or chronic disease. Doctors usually pair IGF-1 with a growth hormone stimulation test or an oral glucose suppression test before making a call.

Research Peptides Marketed as IGF-1

Products sold online as IGF-1 LR3 or similar peptides are not the same thing as the IGF-1 measured in a blood test. IGF-1 LR3 is not FDA-approved for human use in the United States and is sold for laboratory research only.

If your first question is is igf 1 lr3 safe, the honest answer is that human safety and dosing data are limited, and reports of hypoglycemia and tissue growth effects are a genuine concern. The question how does igf 1 lr3 work comes up often too; the short version is that it binds IGF-1 receptors with a much longer half-life than natural IGF-1, which is exactly why unregulated use is risky.

Peptide comparisons are also common. When people weigh igf-1 lr3 vs sermorelin, the key difference is that sermorelin prompts your own growth hormone release while IGF-1 LR3 acts downstream of growth hormone. Neither is a do-it-yourself option, and both belong under medical supervision.

The bottom line is that normal IGF-1 levels by age are a moving target, and your lab's age-specific range is the only one that matters for your result. Discuss any out-of-range value with a physician or pediatric endocrinologist instead of adjusting anything on your own.

COMMON QUESTIONS

Frequently Asked Questions

What is a normal IGF-1 level by age?

Typical ranges run about 50-300 ng/mL in childhood, 150-500 ng/mL during puberty, 90-350 ng/mL in adults, and 50-200 ng/mL after age 70. Every laboratory sets its own interval, so compare your result to the age-matched range printed on your report rather than to a general chart.

What is a normal IGF-1 level for a 40-year-old?

Most labs place a 40-year-old's normal range somewhere around 90-280 ng/mL, though the exact numbers depend on the assay. Because IGF-1 declines after the mid-20s, a value that looks low on a young-adult chart can be completely normal at 40.

Can you raise IGF-1 naturally?

Sleep, adequate protein intake, and regular resistance training support normal growth hormone and IGF-1 production, but they will not push you far outside your genetic range. No over-the-counter supplement has strong evidence for raising IGF-1 meaningfully, and persistent low levels should be evaluated by a doctor.