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Animal data onlyNot FDA approved

IGF-1 LR3

Also known as: Long R3 IGF-I · LR3IGF-I · IGF LR3 · Long Arg3 IGF-1

Updated 20 sources

IGF-1 LR3 is a lab-made version of IGF-1, the hormone GH tells your liver to make. Two changes keep it from sticking to the binding proteins that normally park IGF-1, so more of it is free to act. It was built as a cell-culture reagent, not a drug, and has never been tested in a human study. Bodybuilders run it at 20 to 40 mcg a day, with carbs.
Calculate with IGF-1 LR3Dosage chart

Quick facts

Half-life
  • Not measured in humans. In rats it cleared about 10 times faster than native IGF-1. The 20 to 30 hour figure quoted online has no human source.
Routes
  • Subcutaneous injection
  • Intramuscular injection
Reported dose ranges
  • 20 to 100 mcg (subcutaneous injection)
  • 10 to 20 mcg (intramuscular injection)
Vial sizes
  • 1 mg
FDA status
  • Not FDA approved
WADA
  • Prohibited

What people use IGF-1 LR3 for

  • Muscle growth and fullness in bodybuilding
  • Nutrient partitioning and recovery
  • Site injections into lagging muscles after training
  • An add-on to GH secretagogues or MK-677

How it is thought to work. LR3 swaps in arginine at position 3 and adds a 13-amino-acid tail. Its binding to IGFBP-3 is about 1000-fold lower than native IGF-1, so it acts on the IGF-1 receptor directly. In cells it was 5 to 10 times as potent as IGF-1, and in rats 6 times as potent for growth. Unlike GH secretagogues, it skips the pituitary entirely.

IGF-1 LR3 dosing

10 protocols from studies, guides and community reports, grouped by goal. Tap a source badge to see where a number came from.

Injected10

Forum convention

Amount
20 to 40 mcg
How often
Once daily, after training
Route
Subcutaneous injection
Cycle
4 to 6 weeks on
Rest
Equal time off
Timing and details

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Self-logged doses

Amount
50 to 100 mcg
How often
Per logged entry; median bucket 50 to 100 mcg
Route
Subcutaneous injection
Timing and details

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With a meal

Amount
20 to 40 mcg
How often
Once daily
Route
Subcutaneous injection
Cycle
4 to 6 weeks on
Rest
Equal time off
Timing and details

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Beginner

Amount
20 to 30 mcg
How often
Daily
Route
Subcutaneous injection
Cycle
4 weeks
Timing and details

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Standard

Amount
30 to 40 mcg
How often
Daily, split across the day
Route
Subcutaneous injection
Cycle
4 to 6 weeks at most

Advanced

Amount
40 to 50 mcg
How often
Daily, split across the day
Route
Subcutaneous injection
Cycle
4 to 6 weeks at most

With fast carbs

Amount
20 to 40 mcg
How often
Daily; 20 mcg to start, 40 mcg a day in a 4 on, 4 off plan
Route
Subcutaneous injection
Cycle
4 to 6 weeks at most
Rest
2 to 4 weeks off
Timing and details

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Site injection into a trained muscle (per side)

Amount
10 to 20 mcg
How often
After training, into each side of the trained muscle
Route
Intramuscular injection
Timing and details

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Training days only

Amount
50 mcg
How often
After exercise on protocol days, 150 mcg a week
Route
Subcutaneous injection

Educational chart

Amount
20 to 50 mcg
How often
Daily
Route
Subcutaneous injection
Cycle
8 to 16 weeks, an outlier among guides
Timing and details

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Doses shown are what sources report, labelled by origin. Not medical advice.

Full IGF-1 LR3 dosage guideEvery titration step in syringe units, missed doses and how to mix.

Vial strengths and syringe units

Every IGF-1 LR3 vial size with the water volumes sources use. Units are what to draw on a U-100 insulin syringe, worked out exactly.
IGF-1 LR3: concentration and U-100 syringe units for each vial size and water volume
WaterStrength20 mcgdose, units40 mcgdose, units50 mcgdose, units
1 mg vial
1 mLCompetitor guide1 mg/mL20.02 mL40.04 mL50.05 mL
2 mLCompetitor guide0.5 mg/mL40.04 mL80.08 mL100.1 mL
3 mLCompetitor guide0.333 mg/mL60.06 mL120.12 mL150.15 mL
Units are on a U-100 insulin syringe (100 units = 1 mL). U-50 and U-30 barrels read the same units.Water volumes from

Doses shown are what sources report, labelled by origin. Not medical advice.

Calculate with this peptideYour vial, your water, your dose: IGF-1 LR3 in syringe units, with the math shown.

What people report

What IGF-1 LR3 users write on Reddit, counted post by post. These are reports, not measured rates or advice.

Community-reportedFrom 572 Reddit posts and comments, last mined Oct 23, 2026r/Peptides, r/Biohackers, r/Peptidesource, r/PeptideDiscussion

Doses people report for IGF-1 LR3

Muscle growth36 mentions

Amounts reported for muscle growth, with mention counts
ReportedMentions
50 mcg12
30 mcg8
20 mcg5
100 mcg5
25 mcg2

Goal not stated31 mentions

Amounts reported for goal not stated, with mention counts
ReportedMentions
50 mcg10
20 mcg5
40 mcg5
100 mcg4
400 mcg4

Left out: 5 mentions far outside every sourced protocol, most likely vial sizes or typos.

How often

Dosing frequencies reported, with mention counts
ReportedMentions
Once a day21
5 days on, 2 off3
As needed3
Three times a week2

Most mentioned alongside

Side effects people mention

  • Low blood sugar6 mentions

    Most common fix: eat carbs or sugar (2)

  • Swelling3 mentions

  • Fainting2 mentions

    Most common fix: eat carbs or sugar (2)

  • Fast heart rate2 mentions

  • Fatigue2 mentions

  • Carpal tunnel2 mentions

Doses shown are what sources report, labelled by origin. Not medical advice.

IGF-1 LR3 side effects

What trials and labels report, kept apart from what users and guides report. Frequencies are worded as each source states them.

Reported in studies and labels2

From clinical trials and regulatory documents.

  • Growth-promoting (mitogenic) effects

    A theoretical concern from IGF-1 receptor biology. No human data exist either way

  • Label warnings for approved IGF-1 (mecasermin)

    Mecasermin's label lists severe hypoglycemia, raised pressure inside the skull, enlarged tonsils and malignant neoplasia. It is a different molecule, but the same receptor

    How people manage it

    • The label gives mecasermin shortly before or after a meal or snack.

Reported by users and guides4

From community reports and dosing guides. Not measured rates.

  • Low blood sugar (hypoglycemia)

    The main acute concern in guides, especially at 50 mcg and above. One guide states a 20 to 30% risk with no source. Approved IGF-1 has caused severe hypoglycemia

    How people manage it

    • Take it with food or fast carbs, never fasted.

  • Injection-site irritation

    Reported by guides

  • Brief stomach upset

    Reported by guides

  • Headache

    Reported by guides in weeks 1 to 2

All 6 IGF-1 LR3 side effects and how people manage themEvery management tip, who should not use it, and side-effect questions.

Storage

Powder (before mixing)

Temperature
2 to 8 °C

Fridge at 2 to 8 °C, good for 12 to 24 months per one guide. Another allows room temperature or fridge.

Mixed vial

Temperature
2 to 8 °C
Use within
28 days

Fridge, 2 to 8 °C. Guides give 14 to 30 days, with 28 days as a common figure. Freezing aliquots has not been shown to extend it.

Mixed with: Bacteriostatic water

Mixing. 1 mg is the only vial size found. Doses are tiny, often 2 to 4 units on a U-100 syringe, so the volume you pick changes how precise each draw is. Guidance on acetic-acid reconstitution was not found.

Stacks people report

Combinations from guides and community posts, with the reason given.
  • Ipamorelin

    LR3 after training, ipamorelin 200 to 300 mcg before bed.

  • CJC-1295

    Paired with CJC-1295 with DAC at 2 mg a week.

  • MK-677 (Ibutamoren)

    MK-677 at 12.5 to 25 mg nightly. Guides say to watch insulin sensitivity.

Compare IGF-1 LR3

Evidence and legal status

Evidence: animal data only

No peer-reviewed human studies. Evidence is cell work and rat studies on binding, potency and clearance. It was made as a cell-culture growth reagent; one black-market vial even held a His-tagged lab version. Every dose here is a community or guide convention.

FDA and WADA

Not FDA approved

No approval, no trial program and not on FDA's compounding lists.

Not FDA approved. It is a different molecule from mecasermin (Increlex), the approved recombinant IGF-1 (BLA 021839, approved August 30, 2005). Not named on FDA's 503A category lists or the compounding safety-risk page.

WADA 2026 bans IGF-1 and its analogues at all times under S2.3.

WADA: Prohibited

IGF-1 LR3 questions

How much IGF-1 LR3 per day?

20 to 40 mcg a day is the convention. Guides top out around 50 mcg. Self-logged entries run from about 10 to 100 mcg.

When should I inject it?

After training or with a meal, with carbs. That is the opposite of GH secretagogues, which people take fasted.

How much water goes in a 1 mg vial?

Guides use 1, 2 or 3 mL. At 1 mL, 20 mcg is 2 units on a U-100 syringe; at 2 mL it is 4 units. Use the calculator for your own numbers.

What is the half-life of IGF-1 LR3?

It has not been measured in humans. The 20 to 30 hour figure on many sites has no human source. In rats, LR3 cleared about 10 times faster than native IGF-1 because it does not ride on binding proteins.

Can it cause low blood sugar?

Approved IGF-1 can, and guides warn the same for LR3. Take it with food and keep fast carbs on hand.

How long is a cycle?

4 to 6 weeks on, then the same time off. Some guides use 2 to 4 weeks off.

Can I inject it into a muscle?

Some do, 10 to 20 mcg into each side of a trained muscle after a workout.

What results do people see?

There is no human trial, so before-and-after claims are anecdotal.

Is it the same as Increlex?

No. Increlex (mecasermin) is native-sequence IGF-1 and FDA approved for children with severe primary IGF-1 deficiency, dosed by body weight twice daily with food. It is not a dose reference for LR3.

How is LR3 different from IGF-1 DES?

DES is a shorter, short-acting variant used locally after workouts.

How is LR3 different from HGH?

GH works upstream and raises IGF-1 indirectly. LR3 acts on the IGF-1 receptor directly.

Who should not use it?

One guide lists kidney disease as a do-not-use, based on a rat study where kidney failure changed how LR3 was cleared.

Is it banned in sport?

Yes. WADA lists IGF-1 and its analogues under S2.3, banned at all times.

Ask about IGF-1 LR3

Answers come from this site's pages only, with a link to each source.

Sources

20 sources, each checked by date. Record updated Oct 23, 2026. Numbers are restated in our own words and labelled by where they came from.

Regulatory5

  1. 503A bulk drug substance categories (May 14, 2026)FDA · checked Oct 23, 2026
  2. Certain bulk drug substances, safety risksFDA · checked Oct 23, 2026
  3. openFDA Increlex applicationFDA · checked Oct 23, 2026

Competitor guide11

  1. IGF-1 LR3 protocolPathToPeptides · checked Oct 23, 2026
  2. IGF-1 LR3 dosage guideBodyHackGuide · checked Oct 23, 2026
  3. IGF-1 LR3 dosage chartPeptideDeck · checked Oct 23, 2026

Community-reported2

  1. Performance-enhancing peptides modulating GH-IGF1 axis (Dominikowski 2026)PMC · checked Oct 23, 2026
  2. IGF-1 LR3 (self-logged doses)PeptIQ · checked Oct 23, 2026