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August 15, 2025

IGF-1: Testing, Optimal Levels, and How to Improve Naturally & Clinically

IGF-1 is a vital growth factor impacting muscle, metabolism, and longevity. Learn how to measure, interpret, and optimize your levels naturally and clinically.

IGF-1: Testing, Optimal Levels, and How to Improve Naturally & Clinically

IGF-1: Testing, Optimal Levels, and How to Improve Naturally & Clinically

Insulin-like Growth Factor 1 (IGF-1) is one of the most powerful anabolic hormones in the human body. While it’s most famous for promoting growth during childhood, it plays essential roles throughout life—supporting muscle development, fat metabolism, brain function, and even healthy aging.

IGF-1 is also a key marker of growth hormone activity, making it one of the best ways to assess whether your body is producing enough growth hormone (GH) or if you might benefit from targeted interventions.

In this article, we’ll cover:

  • What IGF-1 is and why it matters

  • How IGF-1 is best measured

  • What your IGF-1 test means

  • Optimal IGF-1 levels for different ages

  • How to raise or lower IGF-1 for optimal health

  • Lifestyle, supplement, and peptide strategies to fine-tune levels

What Is IGF-1?

IGF-1 is a hormone produced primarily in the liver in response to growth hormone (GH) secretion from the pituitary gland. GH stimulates the liver to release IGF-1, which then travels through the bloodstream to stimulate growth and repair in almost every tissue.

Structurally similar to insulin, IGF-1 binds to specific receptors on cells, activating pathways that promote cell growth, protein synthesis, and repair.

Key functions of IGF-1 include:

  • Muscle growth & repair – Stimulates protein synthesis and satellite cell activation for hypertrophy and recovery.

  • Bone health – Promotes bone formation and increases bone mineral density.

  • Metabolic regulation – Enhances fat burning and glucose metabolism.

  • Brain function – Supports neuroplasticity, learning, and memory.

  • Tissue repair – Accelerates healing after injury or illness.

How IGF-1 Is Best Measured

Unlike growth hormone, which is secreted in short bursts and fluctuates wildly throughout the day, IGF-1 levels remain relatively stable. That makes IGF-1 the preferred test for evaluating overall GH status.

Best practices for testing IGF-1:

  1. Fasting blood draw – Morning fasting levels give the most consistent results.

  2. No intense exercise before testing – Vigorous training can temporarily alter IGF-1.

  3. Lab method – Liquid chromatography-tandem mass spectrometry (LC-MS/MS) or high-quality immunoassays are preferred for accuracy.

  4. Context matters – Test alongside other markers such as fasting insulin, glucose, thyroid function, and possibly GH stimulation testing if deficiency is suspected.

Important: IGF-1 is age-dependent. What’s “normal” for a 25-year-old is not the same as for a 65-year-old.

What Your IGF-1 Test Means

IGF-1 results are typically reported in ng/mL, with a reference range that varies by age and sex.

Low IGF-1 may suggest:

  • Growth hormone deficiency

  • Chronic inflammation or illness

  • Poor nutrition or malabsorption

  • Low protein intake

  • Chronic stress or elevated cortisol

  • Liver disease

High IGF-1 may suggest:

  • Excess growth hormone (acromegaly)

  • High protein/calorie intake

  • Insulin resistance or high insulin levels

  • Certain cancers or tumor risk (if sustained at high levels)

  • Use of growth hormone therapy or certain peptides

Optimal IGF-1 Levels

While labs provide wide reference ranges, optimal levels are more specific when considering health, longevity, and performance goals.

General Optimal IGF-1 Ranges (ng/mL):

  • Ages 20–30: 200–350

  • Ages 31–50: 175–300

  • Ages 51–65: 150–250

  • Ages 66+: 125–200

These are functional medicine targets, aiming for the upper half of the age-adjusted range without exceeding it—balancing anabolic benefits with long-term health.

How to Adjust IGF-1 Levels

The goal is balance. Too low can mean muscle loss, frailty, and slower recovery. Too high for too long may increase cancer risk.

1. Nutrition & Lifestyle

To Increase IGF-1:

  • Adequate protein – Aim for 1.2–1.6g/kg body weight daily.

  • Strength training – Stimulates GH release and downstream IGF-1 production.

  • Healthy sleep – Deep sleep is a major GH release window.

  • Balanced carbohydrates – Avoid chronic low-carb if IGF-1 is low, unless medically necessary.

  • Healthy body fat range – Both obesity and extreme leanness can reduce IGF-1.

To Reduce IGF-1 (if elevated):

  • Reduce excessive protein intake – Especially from animal sources, if significantly over 2g/kg.

  • Time-restricted eating or fasting – May reduce chronically high IGF-1 and improve metabolic markers.

  • Lower insulin levels – Managing blood sugar helps normalize IGF-1.

2. Supplements That Support Optimal IGF-1

  • Omega 1300 – Supports muscle repair, reduces inflammation, and enhances cellular signaling.

  • ActiveMulti – Provides essential micronutrients for anabolic processes.

  • CoQ10 Omega – Improves mitochondrial efficiency, indirectly supporting GH/IGF-1 function.

  • Vitamin D3 + K2 – Deficiency may impair IGF-1 signaling.

  • Creatine monohydrate – May modestly enhance IGF-1 signaling in muscle tissue.

3. Peptide Therapies for IGF-1 Optimization

Peptides can help modulate growth hormone release, thereby influencing IGF-1. These are physician-prescribed and sourced from FDA-regulated facilities at Revolution Health.

To Increase IGF-1:

  • CJC-1295 – Stimulates natural GH pulses.

  • Ipamorelin – Synergistic with CJC-1295 for GH release.

  • Tesamorelin – Clinically proven to raise IGF-1 while reducing visceral fat.

  • Follistatin – Enhances muscle growth pathways indirectly tied to IGF-1.

To Lower IGF-1 (if excessively high):

  • This is less common, but strategies may include adjusting GH-related therapies and dietary changes under medical supervision.

4. Medical Considerations

Low IGF-1 with symptoms of GH deficiency may warrant:

  • GH stimulation testing

  • Consideration of GH or peptide therapy under endocrinology or functional medicine guidance

High IGF-1 may require:

  • Acromegaly screening (IGF-1 + oral glucose tolerance GH suppression test)

  • Adjustment of therapy dosages

  • Cancer risk assessment and monitoring

IGF-1, Longevity, and Health Span

The relationship between IGF-1 and lifespan is U-shaped—both extremes are associated with higher risk.

  • Low IGF-1 → Frailty, sarcopenia, poor wound healing, lower bone density.

  • High IGF-1 → Possible increased cancer risk, accelerated cell proliferation without adequate repair balance.

The sweet spot is age-adjusted high-normal, supporting muscle and bone while avoiding overstimulation.

Key Takeaways

  • IGF-1 is a stable, reliable marker of growth hormone activity.

  • It impacts muscle, bone, brain, metabolism, and repair.

  • Testing is best done fasting, with interpretation based on age and symptoms.

  • Both lifestyle and clinical interventions can fine-tune IGF-1 levels.

  • Functional medicine aims for the upper half of age-adjusted ranges, but not beyond.

Next Steps

If your IGF-1 is outside the optimal range, the first step is a comprehensive evaluation with a functional medicine provider who understands both lifestyle interventions and advanced therapies like peptides. At Revolution Health, we specialize in precision hormone and peptide protocols designed to safely optimize your IGF-1 and overall health.