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№ 024

IGF-1 LR3

Used to drive muscle growth. A long-acting form of insulin-like growth factor 1, with limited human safety data and a real side effect profile, handle with discipline.

GH-axis
Evidence: Limited

IGF-1 LR3: Used to drive muscle growth. A long-acting form of insulin-like growth factor 1, with limited human safety data and a real side effect profile, handle with discipline. IGF-1 LR3 is a long-acting form of insulin-like growth factor 1.

FDA ⓘ
Not approved
WADA
Banned
Typical dose
30-60 mcg sub-q daily
Half-life ⓘ
~20-30 hours
Route ⓘ
Subcutaneous
Schedule
Daily
In plain English

IGF-1 LR3 is a long-acting form of insulin-like growth factor 1. Used for muscle anabolism, but human safety data is thin and the side effect profile (low blood sugar, organ growth concerns) is real. Treat carefully, short cycles only.

Status & legalityWhat do these mean? →
Natty? ⓘ
Not natty

Long-acting IGF-1 analog. Universally banned in tested sport.

FDA ⓘ
Not approved

Mecasermin (Increlex) approved 2005 for severe primary IGF-1 deficiency. IGF-1 LR3 specifically (research analog) is NOT FDA approved.

Compounding ⓘ
Category 2

FDA flagged as significant safety risk; restricted from compounding pharmacies.

WADA ⓘ
Banned (S2)
Prescribed ⓘ

Increlex prescribed by pediatric endocrinology for IGF-1 deficiency. IGF-1 LR3 is not prescribed.

Who it's for

  • →Experienced users who already have GH-axis baseline
  • →Short, focused anabolism cycles

What to expect

  1. Week 1

    Pumps and fullness in trained muscle. Mild hypoglycemia risk.

  2. Week 4

    Nutrient partitioning shifts noticeably. Plateau approaching by week 4.

  3. Week 8

    Cycle endpoint already passed. Cycle off well before this point.

Looking at IGF-1 LR3? Your next 3 steps

  1. 1Work out your exact dose

    Vial size + BAC water turns into the exact units to draw for IGF-1 LR3.

    Open calculator →
  2. 2See what to stack & monitor

    The companion supplements and the bloodwork worth tracking on this kind of protocol.

    Bloodwork guide →
  3. 3Save it & ask the Coach

    A free account saves your stack; membership adds the stack-aware AI Coach.

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How it works (mechanism)

Long Arg3 IGF-1, a modified IGF-1 with arginine at position 3 and an N-terminal extension. Resists binding to IGFBPs (which normally sequester IGF-1), giving it ~3x longer half-life and stronger systemic activity than native IGF-1.

Dosing protocol

Members only

Stacks well with

Members only

Side effects

01Hypoglycemia (low blood sugar), eat carbs near dose
02Localized growth at injection site
03Theoretical: visceral organ growth at chronic high doses
04Headache

When NOT to use

  • ⚠Active malignancy (real concern with IGF-1)
  • ⚠Diabetic retinopathy
  • ⚠Pregnancy / nursing
  • ⚠Hypoglycemia-prone

Bloodwork to monitor

  • • Fasting glucose every 2 weeks
  • • IGF-1 baseline + at week 4

Common mistakes

  • • Running it longer than 4 weeks
  • • Dosing fasted (hypoglycemia)
  • • Stacking with insulin or insulin-sensitizers without monitoring

Drug & supplement interactions

  • ⚠Insulin: severe hypoglycemia risk, eat carbs near dose
  • ⚠Glucocorticoids antagonize IGF-1 effects
  • ⚠Cytotoxic chemotherapy: avoid (theoretical malignancy concern)

Community patterns

Members only
Free, no account needed

New to IGF-1 LR3? Grab the starter checklist.

Drop your email and we'll send the one-page first-cycle starter checklist, plus a heads-up if IGF-1 LR3 changes legal status. No account needed.

No spam. No selling your email. Just the checklist and the occasional reclassification alert.

AI Coach, live sample
Members only
is 250mcg of bpc enough for a knee injury?
For a knee, 250 mcg sub-q daily is the standard working dose and a solid place to start. The trick with BPC is consistency, give it weeks, not days. Inject close to the joint, run it 4-6 weeks, and don't drop below 200 mcg, it tends to stop cracking the threshold reliably down there. If it hasn't moved at all by week 3, that's when adding TB-500 earns its place.
how much bac water for a 10mg reta vial?
3 mL is the standard play for a 10 mg reta vial. That's 3,333 mcg/mL, clean unit math across the titration: 2 mg = 60 units, 4 mg = 120 units, 6 mg = 180 units on a 100-unit insulin syringe. Run 2 mL instead if you want fewer, more concentrated shots (5,000 mcg/mL, so 2 mg = 40 units). Since most people titrate up over ~12 weeks, 3 mL keeps the numbers cleanest.
what should i track on bloodwork for tirzepatide?
Lipid panel, ALT/AST (liver enzymes), and an A1C, baseline before you start then every 3 months. If you've got metabolic-syndrome history, add fasting glucose and insulin so you can actually watch insulin sensitivity improve. You don't need a big hormone panel for a GLP-1.

Ask the Coach anything about IGF-1 LR3 or your own stack. This is it working.

Trained only on Pepdex content. Does the dose math, flags interactions, knows your stack. Won't push vendors, won't pretend to be a doctor.

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Frequently asked

What is IGF-1 LR3?+
IGF-1 LR3 is a long-acting form of insulin-like growth factor 1. Used for muscle anabolism, but human safety data is thin and the side effect profile (low blood sugar, organ growth concerns) is real. Treat carefully, short cycles only.
Is IGF-1 LR3 FDA approved?+
Mecasermin (Increlex) approved 2005 for severe primary IGF-1 deficiency. IGF-1 LR3 specifically (research analog) is NOT FDA approved.
Is IGF-1 LR3 legal?+
IGF-1 LR3 is not FDA-approved. It is sold by compounding pharmacies (with a prescription) and as "research only" by peptide vendors. Possession is generally not criminalized but distribution without authorization may be. Verify local laws.
Is IGF-1 LR3 banned by WADA?+
IGF-1 LR3 is on the WADA prohibited list under Banned (S2).
Are you still natty after taking IGF-1 LR3?+
No. Long-acting IGF-1 analog. Universally banned in tested sport.
Do doctors prescribe IGF-1 LR3?+
Increlex prescribed by pediatric endocrinology for IGF-1 deficiency. IGF-1 LR3 is not prescribed.
What's the typical dose of IGF-1 LR3?+
30-60 mcg sub-q daily, post-workout, with carbs nearby to manage hypoglycemia.
What are the side effects of IGF-1 LR3?+
Common side effects include: Hypoglycemia (low blood sugar), eat carbs near dose; Localized growth at injection site; Theoretical: visceral organ growth at chronic high doses; Headache. Less common effects and full safety details are on the entry page.
How long until IGF-1 LR3 starts working?+
Pumps and fullness in trained muscle. Mild hypoglycemia risk.
What can you stack with IGF-1 LR3?+
Common pairings: Standalone for short anabolism windows. Full stacking protocol and timing on the entry page.
Where do people get IGF-1 LR3?+
IGF-1 LR3 is most commonly sold by research-only peptide vendors and by compounding pharmacies (the latter requires a prescription). Pepdex is not a vendor, see /coa for how to verify a Certificate of Analysis before buying from any source, and /guides/scam-vendor-spotting for vendor red flags.
IGF-1 LR3 vs IGF-1 DES, which is better?+
IGF-1 LR3 vs IGF-1 DES: long-acting systemic vs short-acting local IGF-1 variants. Side effect profiles differ. Full head-to-head comparison: https://pepdex.co/compare/igf-1-lr3-vs-igf-1-des

Head-to-head with IGF-1 LR3

Compare
IGF-1 LR3 vs IGF-1 DES →

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