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

Sources

Sources checked: 2026-10-18.

Information only, not medical advice. Peptifacts does not sell anything and does not link to sellers.