IGF-1 LR3 for Longevity?

Happy Friday!

I just dropped a brand-new podcast episode on Spotify, breaking down IGF-1 LR3.

If you’ve been around peptides long enough, you’ve heard the myths.

IGF-1 LR3 was positioned as the holy grail of bodybuilding.

The thing that was supposed to turn you into a 300-pound stage-winning mutant overnight.

And because of that mythology, a lot of people either abused it, used it incorrectly, or dismissed it entirely when it didn’t deliver cartoonish results.

That’s not the use case I care about, and it’s not why I’m talking about it today.

I’m revisiting IGF-1 LR3 because, used correctly, sparingly, and with intention, it has a real place in longevity-focused health optimization.

Not year-round. Not carelessly.

But a few strategic windows per year, primarily around preserving and building muscle, supporting metabolic health, and maintaining healthspan as IGF-1 naturally declines with age.

This email will show you where IGF-1 LR3 actually fits if your goal is to be strong, functional, and cognitively sharp as you age.

Background

IGF-1 LR3 is a synthetic analog of insulin-like growth factor-1, a hormone your body already produces downstream of growth hormone.

Structurally, LR3 was modified with a 13-amino-acid extension and a single amino acid substitution at position three.

That small change dramatically reduces binding to IGF binding proteins and extends its half-life from roughly 12 hours to 20–30 hours.

Originally, this compound lived almost exclusively in research settings. It wasn’t FDA-approved, and it never really entered mainstream clinical medicine. Instead, it found its way into the bodybuilding research community, where it picked up a reputation that frankly did it no favors.

The promise became extreme muscle growth. The expectation became unrealistic. And when people didn’t turn into IFBB pros, they either doubled the dose or wrote the compound off completely.

IGF-1 levels naturally decline with age, and that decline correlates with sarcopenia, slower recovery, reduced bone density, and even cognitive decline.

IGF-1 LR3 was never meant to be abused year-round. It’s a tool. And like most powerful tools, it only makes sense when you know exactly when and why to use it.

Mechanisms

At the cellular level, IGF-1 LR3 binds to the IGF-1 receptor, a tyrosine kinase receptor expressed on nearly every cell in the body. Once activated, it triggers two major signaling pathways known as PI3K-AKT-mTOR and MAPK-ERK.

Essentially, this is a growth-and-repair signal.

Through AKT and mTOR, IGF-1 increases protein synthesis, improves cell survival, and reduces programmed cell death.

Through MAPK-ERK, it supports cell proliferation and differentiation. Because LR3 stays active longer than native IGF-1, this signal is more sustained, not transient.

Most people don’t realize that IGF-1 signaling also supports mitochondrial health.

It increases mitochondrial biogenesis through PGC-1α and PGC-1β, improves energy efficiency, and even promotes mitophagy, the cleanup of damaged mitochondria.

IGF-1 LR3 also reduces cellular senescence and helps preserve telomere length, two markers strongly associated with biological aging.

People hear “IGF” and think only muscle, but the biology goes much deeper than that.

Benefits

The most obvious benefit is muscle preservation and growth.

IGF-1 stimulates satellite cell activation and muscle fiber repair, leading to hypertrophy and, potentially, limited hyperplasia.

As we age, maintaining muscle is imperative for insulin sensitivity, metabolic health, fall prevention, and independence.

But the benefits don’t stop there.

IGF-1 supports bone density by activating osteoblasts and increasing mineral deposition. That matters because fractures and falls are one of the leading causes of mortality later in life.

It also supports connective tissue repair through increased collagen synthesis. I’m not saying it replaces BPC-157 or TB-500, but it absolutely overlaps with those repair pathways.

Then there’s the brain. IGF-1 crosses the blood-brain barrier. It supports neuron survival, synaptic plasticity, and cognitive function.

Lower IGF-1 levels are consistently correlated with cognitive decline, while optimized levels are associated with better memory and learning.

Paradoxically, suppressing IGF-1 may, on paper, extend lifespan, but over-suppressing it accelerates frailty and cognitive decline.

I think we should optimize IGF-1 in a sweet spot that supports healthy muscle and metabolic health, while avoiding supraphysiologic levels in the long term.

Dosing

This is not a beginner peptide. Period.

If someone is brand new to peptides, doesn’t understand blood sugar regulation, or isn’t disciplined with nutrition, this isn’t where I’d start them.

Personally, I like 50–100 mcg per day, used post-workout, with carbohydrates. If someone is very new to IGF-1, I’ll have them start at 20–30 mcg and work up slowly.

I prefer to do shallow IM injections into the muscle group I trained.

Because this is insulin-like, hypoglycemia is the main risk. My rule of thumb is for every microgram of IGF-1, I want at least 0.5–1 gram of carbohydrate.

50 mcg = 25–50g carbs

100 mcg = 50–100g carbs

I prefer post-workout because carbs are already present, and muscle uptake is maximized. I do not recommend using this fasted unless you really know what you’re doing.

Cycle length matters. I like 4–8 weeks on, followed by at least 4–8 weeks off, and no more than 2–3 cycles per year. You will notice diminishing returns after the first few weeks. That’s receptor desensitization, and it’s your cue to stop.

Final Thoughts

IGF-1 LR3 is a double-edged sword.

At the right dose, at the right time, used with intention, it’s one of the most effective tools I’ve used for muscle growth, recovery, and overall vitality.

At the wrong dose, used too often, or layered on top of poor nutrition and metabolic health, it becomes an unnecessary risk.

Used correctly, it fits beautifully into a longevity-focused framework alongside GH peptides, HGH, TRT when appropriate, metabolic optimization, and proper nutrition.

Here’s to a strong, sharp, and intentional 2026!

Best,

Hunter Williams