What Are Normal IGF-1 Levels? How Results Are Interpreted

Are you staring at your lab report wondering what your IGF-1 number means? 

Medical jargon and abbreviations can be confusing. And when it comes to IGF-1 levels, there isn’t a single universal “normal” number. It varies significantly by age and sex, and from person to person. 

In this article, we dig into what IGF-1 is, what the expected ranges look like across different life stages, what low and high results may suggest, and what to do next.

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What Is IGF-1?

IGF-1 stands for insulin-like growth factor 1, which is a hormone produced mostly in the liver in response to growth hormone (GH). When the liver releases IGF-1, it travels through your bloodstream and helps deliver many of the effects associated with GH to your muscles, bones, and other tissues. 

In more practical terms, IGF-1 supports cell growth and repair, helps maintain muscle and bone density, influences how your body uses energy, and plays a role in recovery. 

IGF-1 is frequently used as a measurement of overall GH activity because GH itself fluctuates throughout the day. In contrast, IGF-1 is more stable in the bloodstream, making it a more reliable marker for lab testing.

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Why IGF-1 Is Measured

In children and adolescents, an IGF-1 test is often used to evaluate growth concerns. 

In adults, it may be ordered when there is suspicion of growth hormone deficiency or excess, or to monitor someone already on GH-related therapy.

It also appears increasingly in metabolic and longevity-focused assessments, where it may be considered alongside other clinical information when evaluating age-related or metabolic concerns. 

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Normal IGF-1 Levels by Age and Sex

There’s no single “normal” IGF-1 number. Reference ranges are age- and sex-specific, and a value that would be unusual at 25 can be completely expected at 55.

The ranges below come from Warde Medical Laboratory’s published reference data; these IGF-1 ranges are categorized by age and sex. 

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Keep in mind that reference ranges may differ between laboratories based on testing methodology and the population used to establish the range, so the range printed on your own lab report should be used when interpreting your result.

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It’s worth noting that pediatric ranges look very different from the above. IGF-1 peaks during puberty at roughly 760 ng/mL in males and 678 ng/mL in females around ages 13 to 15, then declines steadily through adulthood.

The ranges above describe what was observed in a healthy reference population. This means that “within range” is more of a statistical description, and does not by itself confirm or rule out a medical condition. Depending on your symptoms and context, a result near the bottom-end of your age-matched range may still be worthwhile discussing with a provider.

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Why IGF-1 Declines With Age

As you age, the pituitary produces less GH. With less GH signaling to your liver, IGF-1 output also declines. For most, this decline begins in their late 20s to early 30s and continues gradually across the following decades. In other words, it’s normal and expected.

However, IGF-1 levels and age-related patterns may differ between individuals and may be influenced by factors including body composition, sleep, nutrition, activity level, and overall health. In some cases, this variability may prompt further evaluation, which may help determine whether growth hormone support is clinically appropriate. 

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What Factors Affect IGF-1 Levels Beyond Age

Even within the same age group, IGF-1 may vary. Several factors may contribute to this, including:

• Nutrition and caloric intake: IGF-1 is sensitive to nutritional intake. As such, sustained caloric restriction, low protein intake, or malnutrition may suppress it even in otherwise healthy people. In contrast, adequate protein intake may support its production.
• Sleep: GH is released primarily during deep sleep. In turn, insufficient or poor-quality sleep may affect normal GH secretion and may influence IGF-1 levels. 
• Body composition: Higher muscle mass is generally associated with higher IGF-1. In contrast, obesity, particularly in people with higher visceral fat, may be associated with altered GH-IGF-1 signaling.
• Exercise: Regular resistance training and higher-intensity exercise may influence GH secretion and IGF-1 signaling, although responses can vary based on the type, intensity, and duration of exercise. 
• Chronic illness and medications: Liver disease, hypothyroidism, and inflammatory conditions may lower IGF-1, as may medications such as corticosteroids. If you have any of these conditions or take these medications, a licensed provider is your best resource to determine your next best step.
• Sex hormones: Estrogen and testosterone both influence IGF-1 production. This means that changes during menopause or andropause may contribute to declining levels.

With many variables in play, a single IGF-1 result is best interpreted alongside your symptoms, history, and other labs—and this is best done by a licensed healthcare provider who knows your current health status and history.

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What Low IGF-1 Levels May Mean

Low IGF-1 refers to a result below the lower bound of your age- and sex-matched range. That is different from “low-normal,” which means you are technically within range but near the bottom of it. However, both instances may be worth a conversation with a licensed provider, depending on how you feel and other symptoms.

A low IGF-1 result may be associated with:

• Growth hormone (GH) deficiency (which may present as persistent fatigue, reduced muscle mass, increased body fat, slow recovery from exercise, and changes in sleep quality)
• Nutritional deficiencies or malnutrition
• Liver dysfunction (since the liver is where most IGF-1 is produced)
• Hypothyroidism
• Ongoing poor sleep or certain chronic health conditions

A low IGF-1 result doesn’t automatically mean you have a GH deficiency. Always discuss your results with a licensed provider. A provider will typically account for your symptoms, consider additional testing, and evaluate your full health picture before drawing any conclusions.

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What High IGF-1 Levels May Mean

A result above the upper bound of your age- and sex-matched range is less common than a low IGF result. But it also warrants provider evaluation. 

Elevated IGF-1 may be associated with:

• Acromegaly (a rare condition involving excess GH production that usually stems from a pituitary tumor and tends to come with distinctive physical changes)
• Gigantism in children (which is also rare)
• Certain cancers (though the relationship here is complex and still being studied;  Elevated IGF-1 has not been shown to cause cancer.)
• Use of exogenous growth hormone or GH-stimulating therapies without medical oversight

When GH-related therapy is deemed appropriate by a licensed provider, they typically monitor IGF-1 levels regularly; this allows your provider to adjust your treatment accordingly. And this is why working alongside a healthcare professional is important.

If your result is above the range for your age and sex, discuss it with a licensed healthcare provider promptly.

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How to Read Your IGF-1 Lab Results

If you’re currently looking at your lab report, trying to make sense of it, here is what you can do:

1. Find the reference range on your report. Most reports print the expected range next to your result. Ranges differ slightly between labs depending on methodology and reference population, which is normal. 
2. Match your result to your age and sex. A number that looks low against a 25-year-old’s range may be entirely appropriate for someone at 55. Always compare against the age- and sex-matched range.
3. Note whether you are within range, below range, or above range. Each points toward a different conversation with your provider, as covered in the sections above.
4. Consider the context of the draw. Recent illness, a significant diet change, or a stretch of poor sleep around your blood draw may be relevant to how your provider interprets your result. 
5. Bring your results to a provider. Lab results are merely the starting point of a conversation with a healthcare provider; further testing or evaluation may be done to determine what’s actually going on and what the next best step involves.

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When to Talk to a Provider About Your IGF-1 Levels

You may want to consider prioritizing a conversation with a healthcare professional if:

• Your result falls below the lower bound of your age- and sex-matched range.
• Your result falls above the upper bound.
• Your result is within range, but you have persistent, nonspecific symptoms that may warrant further evaluation, such as persistent fatigue, reduced muscle mass, increased body fat, poor sleep, or slow recovery.
• You are on, or considering, any GH-related therapy and want to track your levels.
• You have a chronic condition that may affect IGF-1, such as liver disease or a thyroid disorder.

Ultimately, a licensed healthcare provider can determine whether further testing is needed, such as GH stimulation testing, whether lifestyle factors are contributing, and whether treatment is appropriate for you.

For adults whose provider determines that further treatment may be clinically appropriate, the provider may discuss available options, which can include compounded sermorelin, a peptide that signals the pituitary to produce more of its own growth hormone rather than replacing it directly. However, compounded sermorelin is not FDA-approved. Compounded medications do not undergo FDA review for safety, effectiveness, or manufacturing quality and are available only when prescribed by a licensed healthcare provider based on an individual clinical evaluation. 

Whether it makes sense for you depends on your labs, symptoms, and health history, which is why an evaluation comes first. If you’re curious to learn more, read more about it on our sermorelin treatment page.

Eden’s process starts with a short online intake; from there, Eden connects you with a licensed provider who reviews your history, goals, and lab work. If treatment is appropriate, your provider determines an appropriate treatment plan based on your individual clinical needs.

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