IGF-1 LR3 side effects and risks
An unapproved growth signal with no human trials found.
Also called: Long R3 IGF-I, Long Arg3 IGF-1, LR3-IGF-1, Long-[Arg3]IGF-I.
IGF-1 and analogues · Modified IGF-1 receptor agonist · Evidence: Animal studies only.
Reported side effects
- Low blood sugar: LR3 rate unknown. Related mecasermin can cause severe low blood sugar., serious. Sweating, shaking, confusion or fainting need prompt blood sugar assessment. (source)
- Unwanted tissue or organ growth: Organ growth occurred in guinea pigs; human incidence is unknown., serious (source)
- Fluid retention, tingling or joint pain: Possible class effects; no LR3 specific human rate is available., moderate (source)
- Injection-site reactions or infection: No LR3 incidence estimate. Unregulated injectable quality adds risk., serious (source)
- Cancer-related concerns: A growth signalling concern, not a measured LR3 cancer rate., serious (source)
Stop and get help if
- Confusion, fainting, seizure or low blood sugar that persists: Stop exposure and get emergency care. Do not give food or drink to someone unconscious.
- Trouble breathing, facial swelling or widespread hives: Stop exposure and get emergency care.
- Severe headache with vomiting or new vision changes: Stop exposure and seek urgent care. Mecasermin, a related drug, can raise pressure around the brain.
- Chest pain, severe breathlessness or collapse: Get emergency care now.
- Fever with spreading redness, severe pain or swelling at an injection site: Seek urgent care for possible infection.
Who should avoid it
- pregnant: No human reproductive safety data.
- breastfeeding: Transfer into milk and infant effects are unknown.
- tryingToConceive: Reproductive safety is unknown. This is a precaution.
- under18: No human LR3 pediatric dose has been studied.
- activeCancer: Block active or suspected cancer because LR3 activates growth signalling.
- cancerHistory: Past cancer or a cancer-predisposing condition needs specialist review before growth-factor exposure.
- diabetes: LR3 may lower blood sugar. Human use in diabetes is unstudied.
- diabeticRetinopathy: Human IGF-1 research found worse diabetic eye disease. LR3 risk is unknown.
- seizureDisorder: Low blood sugar can trigger seizures. LR3 risk is unknown.
- sleepApnea: Related mecasermin can enlarge tonsils and obstruct breathing; LR3 risk is unknown.
- heartCondition: Swelling and heart effects need review. LR3 heart safety is unknown.
- kidneyDisease: No human LR3 clearance or dose-adjustment data.
- liverDisease: No human LR3 clearance or dose-adjustment data.
- surgeryPlanned: Fasting or blood sugar medicines need review for low blood sugar.
- other: Severe IGF-1 or ingredient allergy blocks re-exposure, as with related mecasermin.
- testedAthlete: WADA prohibits IGF-1 analogues at all times under S2.3.
Interactions
- Insulin: Expected additive low-blood-sugar risk. No LR3 interaction trial exists.
- Sulfonylureas and other insulin releasers: These medicines lower blood sugar; adding LR3 could compound that effect.
- Other IGF-1 products: LR3 combination safety is unknown.
- Growth hormone and GH secretagogues: People stack these to increase GH/IGF signalling. LR3 combination safety has not been studied.
Product quality risks
- A tested black-market vial contained LR3 with an extra His6 purification tag, not the expected finished molecule.
- A doping-laboratory report also identified unpurified LR3. Neither paper estimates today's market-wide failure rate.
- FDA found poor sterile-production practices at a facility that compounded LR3 among other unapproved products.
Related to IGF-1 LR3
- Mecasermin: Prescription IGF-1 approved for rare childhood growth failure; low blood sugar is a major risk.
- Retatrutide: An experimental weekly injection with phase 3 weight-loss results.
- Somatropin: Prescription human growth hormone, with no proven anti-aging benefit.
Sources
- 21 CFR 216.23 — Bulk drug substances that can be used to compound drug products in accordance with section 503A of the Federal Food, Drug, and Cosmetic Act., Office of the Federal Register · eCFR · 2026
- 503B Bulk Drug Substances List, FDA · FDA · 2026
- Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act, FDA · FDA · 2026
- Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act, FDA · FDA · 2026
- Cellulitis, NHS · NHS · 2026
- The 2026 Prohibited List, World Anti-Doping Agency · WADA · 2026
- Therapeutic Goods (Poisons Standard—October 2026) Instrument 2026, Australian Government · Australian Government · 2026
- INCRELEX (mecasermin) injection, for subcutaneous use, U.S. Food and Drug Administration · FDA · 2025
- Anaphylaxis, NHS · NHS · 2023
- Low blood sugar (hypoglycaemia), NHS · 2023
- Tailor Made Compounding LLC - 594743 - 04/01/2020, FDA · FDA · 2020
- Increlex, European Medicines Agency
- Increlex, INN-mecasermin, European Medicines Agency
- Know When to Go to the ER, American College of Emergency Physicians · American College of Emergency Physicians
- Mecasermin (Increlex▼): risk of benign and malignant neoplasia, MHRA
Sources checked: 2026-10-18.
Information only, not medical advice. Peptifacts does not sell anything and does not link to sellers.