IGF-1 LR3 Quick Start
IGF-1 LR3 is a recombinant analog of IGF-1 carrying an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. Those two changes sharply reduce binding to IGF-binding proteins, so far more of the molecule stays free and active — the reason it is described as substantially more potent than native IGF-1 and why its dosing sits in the low-microgram range. It is a recombinant protein rather than a short synthetic peptide, and it is handled accordingly.
This guide is an educational research reference. It does not diagnose, treat, or prescribe, and is not medical advice. Consult a licensed clinician before considering any compound.
IGF-1 LR3 Dosing Protocol
IGF-1 LR3 is dosed in micrograms, not milligrams — a distinction that matters more here than almost anywhere else on this site, because the vial is 1 mg total and a single misplaced decimal is a fifty-fold error. Ranges below are community-derived research-planning references, not personal dosing recommendations.
Injection — Subcutaneous
| Band | Per dose | Frequency |
|---|---|---|
| Low | 20 mcg | Once daily |
| Standard | 40 mcg | Once daily |
| High | 50 mcg | Once daily |
Cycle guidelines
| Approach | Duration | Review point | Best for |
|---|---|---|---|
| Standard | 4 weeks | Week 2 | Short research blocks |
| Extended | 4–6 weeks | Week 4 | Longer protocols; receptor downregulation is a stated concern |
IGF-1 LR3 Reconstitution Guide
IGF-1 LR3 is a protein, not a short synthetic peptide, and it is the most handling-sensitive item in this catalog. It is supplied at protein grade (SDS-PAGE / RP-HPLC), and the listing specifies avoiding freeze-thaw cycles — each one degrades a fraction of the material irreversibly.
Injection
| BAC | Conc. | 20 mcg | 50 mcg |
|---|---|---|---|
| 1 mL | 1,000 mcg/mL | 2 u | 5 u |
| 2 mL | 500 mcg/mL | 4 u | 10 u |
Units are U-100 insulin-syringe units. The larger volume is preferable here purely for readability — a 2-unit draw has little margin for error.
Freeze-thaw
Aliquot before freezing if long-term storage is needed. Repeatedly freezing and thawing one vial degrades the protein; this is the most common way research material is silently ruined.
Reconstitution steps
- Inspect the vial. Confirm the label, expected milligram amount, and that the powder looks dry and intact.
- Wipe the stoppers. Use an alcohol swab on both the bacteriostatic water and peptide vial stoppers.
- Draw the chosen volume. 2 mL into the vial — this is the number that sets every concentration figure above.
- Inject down the wall. Release the water slowly down the inside wall, not directly onto the powder.
- Swirl, do not shake. Roll gently until dissolved. Shaking foams and can damage the peptide.
- Verify clarity. Solution should be clear and colorless. Some protocols dissolve IGF-1 analogs in dilute acetic acid before diluting with bacteriostatic water, because solubility at neutral pH is limited — follow the COA or supplier guidance rather than assuming.
- Label and refrigerate. Note the date and volume added on the vial, then store at 2–8 °C. Do not freeze the reconstituted solution.
See the bacteriostatic water guide for diluent handling, or the reconstitution calculator to work any other volume.
How IGF-1 LR3 Works
IGF-1 LR3 binds the IGF-1 receptor, a tyrosine kinase that activates the PI3K/Akt and MAPK cascades governing cell growth, protein synthesis and survival signalling. The Arg3 substitution and N-terminal extension reduce affinity for the IGF-binding proteins that normally sequester circulating IGF-1, so the free fraction — and therefore the active fraction — is far higher than native IGF-1 at the same mass.
IGF-1 receptor
Tyrosine kinase driving PI3K/Akt and MAPK growth signalling.
Reduced IGFBP binding
The defining modification; a much larger share stays free and active.
Insulin-receptor cross-talk
Structural similarity to insulin is the basis for the hypoglycaemia risk.
Open question
Because it is systemic rather than local, tissue selectivity is limited — growth signalling is not targeted.
Who Should Avoid IGF-1 LR3
IGF-1 is a growth factor with systemic proliferative signalling, which makes eligibility a clinical question rather than a dosing one.
Active or prior cancer
The most consistently flagged contraindication in this catalog — IGF-1 signalling is directly proliferative.
Diabetes or hypoglycaemia risk
Insulin-receptor cross-reactivity can drop blood glucose; a standard exclusion.
Pregnancy & lactation
No human safety data.
Tested athletes
Prohibited under WADA S2 at all times; growth factors are explicitly named.
IGF-1 LR3 Side Effects & Safety
Hypoglycaemia
The principal acute risk, dose-dependent and potentially rapid. The defining safety consideration for this compound.
Proliferative signalling
IGF-1 promotes cell growth without tissue selectivity — a theoretical oncological concern unresolved in humans.
Injection-site reactions
Reported; rotate sites.
Quality-control risk
Recombinant proteins are harder to verify than short peptides — purity grade and correct folding both matter. Check the COA method.
Timeline & What to Monitor
| Timeframe | Commonly tracked | Notes |
|---|---|---|
| Hours 0–4 | Glycaemic response | The acute window for the hypoglycaemia risk. |
| Week 1–2 | Tolerability, injection-site response | Anti-doping violation applies immediately for tested athletes. |
| Week 4–6 | Protocol review point | Receptor downregulation is a stated reason for limiting duration. |
IGF-1 LR3 Evidence Context
IGF-1 biology
Extensively characterised; IGF-1 is a central growth-axis mediator with a large literature.
LR3 analog
Developed primarily as a cell-culture reagent, where the reduced IGFBP binding is the useful property.
Human data
Essentially absent for this analog as an administered compound; it is not an approved therapeutic.
Open question
Almost everything about systemic administration in humans is uncharacterised — treat community figures as conventions, not evidence.
Storage & Handling
| State | Storage | Notes |
|---|---|---|
| Lyophilized (powder) | −20 °C; −80 °C long-term | Protein-grade storage; more stable than solution. |
| Reconstituted (liquid) | 2–8 °C | Avoid freeze-thaw cycles — aliquot instead. |
| Appearance | Clear, colorless | Discard cloudy or particulate solutions. |
This is the only item in the catalog where the listing calls out −80 °C and freeze-thaw avoidance. Treat those as the actual requirements, not conservative suggestions.
IGF-1 LR3 vs native IGF-1
| Feature | IGF-1 LR3 | Native IGF-1 |
|---|---|---|
| Length | 83 aa (13-aa extension) | 70 aa |
| IGFBP binding | Substantially reduced | High — most is bound and inactive |
| Free fraction | High | Low |
| Practical effect | Active at far lower mass | Largely sequestered |
Frequently Asked Questions
What makes LR3 different from regular IGF-1?
An Arg3 substitution plus a 13-amino-acid N-terminal extension sharply reduce binding to IGF-binding proteins. Far more stays free and active, so it works at much lower mass than native IGF-1.
How is it dosed?
In micrograms. Community references sit around 20–50 mcg once daily. At 500 mcg/mL, 40 mcg is 8 units on a U-100 syringe.
What is the main safety concern?
Hypoglycaemia. IGF-1 cross-reacts with the insulin receptor, and the effect can be rapid and dose-dependent. This is the compound's defining risk.
Why does handling matter so much?
It is a recombinant protein rather than a short synthetic peptide. Freeze-thaw cycles degrade it irreversibly, so aliquot rather than repeatedly freezing one vial.
Is it banned in sport?
Yes. Growth factors including IGF-1 and its analogs are prohibited at all times under WADA S2.
Is this page medical advice?
No. It is an educational research reference and does not diagnose, treat, or prescribe. Consult a licensed clinician before considering any compound.
IGF-1 LR3 Formats & Sourcing
IGF-1 LR3 is supplied as a lyophilized recombinant protein in a single 1 mg vial, at protein purity grade (≥95% by SDS-PAGE / RP-HPLC) rather than the ≥98% HPLC used for short peptides — a different assay for a different class of molecule, not a lower standard.
| Format | Supplied as |
|---|---|
| Vial | 1 mg lyophilized recombinant protein |
Strengths are listed as sold; confirm against the product page and the batch COA before calculating anything.
Reference material for this protocol, with batch COA:
View IGF-1 LR3 on Spyro Peptides →References
- Francis GL, et al. Insulin-like growth factor (IGF)-II binding to IGF-binding proteins and IGF receptors. Biochem J (1993).
- Tomas FM, et al. Long-R3-IGF-I insulin-like growth factor analogue. J Endocrinol (1993).
- Clemmons DR. Modifying IGF1 activity: an approach to treat endocrine disorders. Nat Rev Drug Discov (2007).
- World Anti-Doping Agency. Prohibited List 2025 — S2 peptide hormones, growth factors.