IGF-1 LR3: research, side effects and dosage in studies
In short
IGF-1 LR3 is a laboratory-modified version of human IGF-1. It has never been approved for human use, and it is a banned substance in sport [1]D. Its use rests on cell culture and animal experiments, not on human studies.
- No known human studies. We know of no published clinical study of IGF-1 LR3.
- The substance and its related analogues are banned in sport and have never been approved for human use [1]D. On the WADA list they are in class S2, which is prohibited at all times [13]regulator.
- Its established use is as a laboratory reagent: it replaces insulin in cell culture media [2, 3]D.
- Black-market products examined by doping control laboratories contained unpurified and oxidised LR3-IGF-1 [1, 4]D.
- There is no approved dosage. All published doses are cell culture concentrations or animal doses.
What is IGF-1 LR3?
IGF-1 LR3 is a synthetic analogue of human insulin-like growth factor 1 (IGF-1), called LongR3-IGF-I and Long R3 IGF-1 in the literature [1]D.
IGF-1 is the body's own growth factor, made mainly by the liver under the control of growth hormone [6]. LR3 is a modified form of it, and the same analogue family includes Des(1-3)-IGF-I and R3-IGF-I [1]D.
Here is a point that is often confused online. There is an approved medicine made of human IGF-1, mecasermin [5]. IGF-1 LR3 is not that medicine. It is a different molecule and has never been approved for human use [1]D.
Nor is IGF-1 LR3 growth hormone, although it acts on the same hormone system. A review classes it among unregulated substances marketed as "research chemicals" that modify the growth hormone and IGF-1 axis, together with sermorelin, tesamorelin, CJC-1295, GHRP-2, GHRP-6, hexarelin, ipamorelin and AOD-9604, among others [6].
This site has its own pages on several substances acting on the same axis, including sermorelin, ipamorelin, CJC-1295 and tesamorelin. Basics: What are peptides?. All substances: Peptides A-Z.
Evidence at a glance
Each cell gives the kind of study and its source. The letter is the evidence level, not the result.
| Claimed effect | Humans | Animals | Cells |
|---|---|---|---|
| Muscle growth or performance | None known to us | - | - |
| More growth | - | Daily gain increased in artificially reared piglets in one of two experiments [7]C | - |
| Replacing insulin in cell culture | - | - | Replaced insulin in stem cell differentiation [2]D; used in CHO cell cultures [3]D |
| Effect compared with ordinary IGF-1 | - | - | No difference in maturation or cell death of bovine oocytes [8]D |
| The body's own IGF-1 | - | In pigs, infusion lowered blood IGF-1 [7]C and liver IGF-1 messenger RNA [9]C | - |
| Detection in doping tests | Method validated with the substance added to human serum [1]D | Administration studied in rats [1]C | - |
| Safety | No human study known to us. Harms of the substance class described in a review [6] | - | - |
"-" = no such study is known.
What is IGF-1 LR3 studied for?
IGF-1 LR3 is not studied as a medicine. It is used as a laboratory tool and studied as a target of doping control. We know of no treatment study in humans.
- Cell culture: LR3-IGF-1 can replace insulin in serum-free culture media. This has been shown both in stem cell differentiation [2]D and in the CHO cell cultures used in industry [3]D. It is the substance's most established use and the reason it is made.
- Animal and cell research: it is used as a comparison substance or growth factor alongside IGF-1, for example in maturing bovine oocytes [8]D and in growth studies in pigs [7, 9]C. In these studies the subject is the IGF-1 system, not LR3 itself.
- Doping control: detection methods have been developed and validated for IGF-1 analogues because they are used in bodybuilding [1, 10]D.
How does IGF-1 LR3 work?
IGF-1 LR3 acts at the lower end of the growth hormone and IGF-1 axis as an analogue of IGF-1. Growth hormone and the substances that release it, such as sermorelin and CJC-1295, act at the upper end of the axis [6].
In cell cultures LR3-IGF-1 worked as a growth factor in place of insulin [2, 3]D. In rats it had earlier been found more potent than ordinary IGF-1 [7]C.
In pigs, LR3-IGF-1 infusion lowered the blood level of the body's own IGF-1 [7]C and liver IGF-1 messenger RNA [9]C. So the analogue given from outside does not simply add to the system; the body cuts its own production. The mode of action has not been studied in humans.
Has IGF-1 LR3 been studied in humans?
Not as far as we know: we know of no published human study of IGF-1 LR3, and the substance has never been approved for human use [1]D.
Doping control researchers state plainly that IGF-I and its analogues LongR3-IGF-I, Des(1-3)-IGF-I and R3-IGF-I are banned substances in sport, and although they were never approved for human use, they are readily available as black-market products for bodybuilding [1]D.
The closest human-related study is analytical. The detection method was validated by adding the analogues to human serum [1]D, and the actual administration experiment was done in rats, injected into muscle [1]C. The subject was the test method, not a treatment.
The literature consists of cell culture, animal experiments, cancer cell lines and doping analytics. We know of no clinical or randomised trials.
Promising, but only in animal and cell studies
This finding comes from animals and has not been studied in humans. Results of animal studies cannot be carried straight over to humans.
-
Growth no human studies
In artificially reared newborn piglets, LR3-IGF-1 infusion increased daily gain and milk intake in the later period of the experiment, when milk was freely available. In the first experiment, with restricted feeding, the growth factors had no effect on weight gain [7]C.
If it held in humans: the substance could affect growth and tissue building.
Why it might not translate: the study was in piglets, and an artificially reared newborn animal is in a completely different state of growth from an adult human. Animal doses cannot be converted into human doses by body weight. In addition, in bovine oocytes LongR3-IGF-1 worked no better than ordinary IGF-1 for maturation or cell death [8]D, so the assumed advantage of the analogue did not show in that setting.
Evidence now: there are several animal and cell studies spanning decades, but we know of no published human study.
Who studies IGF-1 LR3?
IGF-1 LR3 is studied mainly by doping control laboratories and by cell and animal researchers, not by drug developers.
Doping analytics papers come, for example, from the laboratory of the French anti-doping agency [1]D and the doping control laboratory of the German Sport University Cologne [4, 10]D. Animal experiments have been done in Australia [7, 9]C and cell experiments in Brazil, for example [8]D.
Who wrote this page: the editorial team
This page was written by the Molecular Recovery editorial team. The draft was made with the help of AI, and the claims were checked against the sources (AI policy). The page has not been medically reviewed. How we work: About us.
What are the side effects of IGF-1 LR3?
There is no research evidence on the harms of IGF-1 LR3 in humans, because there are no human studies. Harms of the substance class have been described in a review [6]. Peptide harms more generally: side effects in studies.
Reported harms of the substance class
For peptides that modify the growth hormone and IGF-1 axis and are marketed as "research chemicals", reported harms include hormonal and metabolic disturbances such as rises in prolactin and cortisol, appetite changes and blood glucose disturbances, as well as fluid retention, muscle and joint pain and injection site reactions [6].
These are observations covering several substances, not measurements made with IGF-1 LR3. Some of them, such as the rise in prolactin and cortisol, were measured with growth hormone releasers such as hexarelin and GHRP-2, not with IGF-1 LR3. The same review notes that these substances have no regulatory approval for body shaping or performance use [6].
The closest comparison: an approved IGF-1 medicine
The closest comparison is the approved IGF-1 medicine mecasermin (Increlex). According to its summary of product characteristics, low blood sugar is a very common adverse reaction: in clinical trials it occurred in 28% of patients [12]official. No such data exist for IGF-1 LR3, which is a different molecule from mecasermin.
Product quality as a harm in itself
For IGF-1 LR3 this is unusually well documented. In a doping control study, black-market products showed abundant signs of lower quality and oxidised peptide forms, so both the native and the once-oxidised form were included in the test method [1]D.
An analysis of confiscated products at the Cologne doping control laboratory found unpurified long-R3-IGF-1, as well as vials labelled as growth hormone that contained no active substance at all [4]D.
Interactions and who has no data
There are no data on interactions with other medicines, and none on pregnancy, breastfeeding or children, because there are no human studies at all. Nor is there any published human study of combining it with growth hormone.
Evidence against and what is unknown
The assumed advantage of the analogue over ordinary IGF-1 did not show in a direct comparison, and efficacy in humans has not been studied at all [8]D.
Evidence against
- When LongR3-IGF-1 and ordinary IGF-1 were compared at the same concentration, 100 nanograms per millilitre, in maturing bovine oocytes, there was no statistical difference between the groups in maturation or cell death. Differences were found only in the expression of single genes [8]D.
- In pigs, a short LongR3-IGF-I infusion reduced the liver's own IGF-I messenger RNA [9]C. A growth factor given from outside does not simply raise the overall activity of the system; the body turns its own production down.
- In piglets the growth effect appeared in only one of two experiments [7]C.
What the evidence does not support
- "IGF-1 LR3 works in humans": there are no human studies of efficacy.
- "IGF-1 LR3 is an approved medicine or its equivalent": it is not. Mecasermin is an approved human IGF-1 product [5]; IGF-1 LR3 is a different substance that has not been approved [1]D.
- "A daily dose or a dose in millilitres is known": no dosing instruction has any basis in human studies.
- "The product you buy contains what the label says": analyses of confiscated products found unpurified and oxidised substance [1, 4]D.
IGF-1 LR3 dosage in studies
IGF-1 LR3 has no approved dosage, and we know of no published human dose. The figures below are cell culture concentrations and animal doses, not recommendations.
| Study | Who | Dose and route | Duration |
|---|---|---|---|
| Araujo 2020 | 739 bovine cumulus-oocyte complexes, cell culture | LongR3-IGF-1 100 ng/ml in the medium; IGF-1 100 ng/ml for comparison | 22-24 hours [8]D |
| Bieberich 2005 | stem cells, cell culture | LongR3-IGF-1 in place of insulin | Not reported [2]D |
| Morris 2000 | CHO cells, cell culture | LongR3 in place of insulin in a serum-free medium | Not reported [3]D |
| Mongongu 2021, animal dose | rats | 100 µg/kg into muscle, single dose, to study detection | 36 hours of follow-up [1]C |
| Dunshea 2002, animal dose | artificially reared newborn piglets | LR3-IGF-1 2-16 µg per hour as a continuous infusion | 8-18 days [7]C |
| Dunaiski 2002, animal dose | pigs of about 55 kg | LongR3-IGF-I 180 µg/kg per day as an infusion | 4 days [9]C |
What the numbers do not tell you. These are not human doses, and no human dose can be derived from them. A cell culture concentration in nanograms per millilitre describes the amount in a test tube, not a dose in the body. The dose given into rat muscle was for developing a test method, not a treatment dose, and animal doses are not converted into human doses by body weight. Because there are no human studies, no safe or effective human dose is known. For that reason IGF-1 LR3 has no dose page or calculator of its own. How to read study doses in general: doses in studies.
IGF-1 LR3 and growth hormone: what is the difference?
IGF-1 LR3 and growth hormone act on the same hormone system at different points, and their regulatory status differs.
Growth hormone acts higher up: it makes the body, mainly the liver, produce IGF-1. IGF-1 LR3 is an analogue of IGF-1, so it acts directly at the lower end of the system [6].
The essential difference is approval. There is an approved human IGF-1 product, mecasermin [5]. IGF-1 LR3 has not been approved for human use [1]D.
We know of no direct comparative human study of IGF-1 LR3 and growth hormone, or of any human study of IGF-1 LR3. One substance acting at the upper end of the axis is tesamorelin [6].
Is IGF-1 LR3 legal in Finland?
IGF-1 LR3 has no marketing authorisation in Finland, so it may not be sold or marketed as a medicine.
The substance has not been approved for human use [1]D. In Finland, Fimea is responsible for marketing authorisations and supervision of medicines; an overview is on the page Peptides and the law in Finland. Fimea has separately warned against using injectable peptides bought online [11]regulator. Bringing them back from travel: Travelling with peptides.
For this substance the label "research use only" is unusually accurate: the established use of LR3-IGF-1 is as a laboratory reagent in cell culture [2, 3]D. The label says what the product is meant for; it is not a permit for human use.
This is not legal advice. Disclaimer.
Is IGF-1 LR3 doping?
Yes. On the WADA 2026 Prohibited List, IGF-1 and its analogues are in class S2.3 (growth factors), and class S2 substances are prohibited at all times, in and out of competition [13]regulator. Doping laboratory researchers state the same for LongR3-IGF-I [1]D.
That is why detection methods have been developed for it. A method published in 2021 isolates LongR3-IGF-I, Des(1-3)-IGF-I and R3-IGF-I with an antibody and identifies them with high-resolution mass spectrometry. In rats, LongR3-IGF-I injected into muscle disappeared from the blood quickly, but its breakdown products were still found after 16 hours [1]C. A broader method for peptides of 2-10 kilodaltons in doping control urine samples has also been developed, and it includes the IGF-1 analogues [10]D.
Competitive athletes should check the current status with their sport federation and anti-doping agency, because the lists are updated every year.
How to assess an IGF-1 LR3 product
For this substance, product quality is a documented problem, not a theoretical risk.
In a doping control method study, black-market products showed abundant signs of lower quality and oxidised peptide forms [1]D. An analysis of confiscated products at the Cologne laboratory found unpurified long-R3-IGF-1 [4]D.
Oxidation matters because it may not show as a single purity figure. On a certificate of analysis (COA) look at the method: liquid chromatography, HPLC, gives purity and mass spectrometry (MS) identifies the molecule, and the oxidised form differs in mass from the original. A guide: How to read a COA.
IGF-1 LR3 is a much larger molecule than the short peptides covered on this site: in doping analytics it belongs to the group of peptides of 2-10 kilodaltons [10]D. The longer the molecule, the more ways it can be partly wrong. Handling and storage: Mixing and storage.
FAQ
What is IGF-1 LR3?
A synthetic analogue of human IGF-1, called LongR3-IGF-I in the literature. It has never been approved for human use, and it is banned in sport [1]D. Its most established use is as a laboratory reagent in cell culture [2, 3]D.
What is the dosage of IGF-1 LR3?
There is no human dose, because there are no human studies. The published doses are cell culture concentrations, such as 100 nanograms per millilitre [8]D, and animal doses, such as 100 µg/kg into rat muscle for developing a test method [1]C.
What is the daily dose or the dose in millilitres of IGF-1 LR3?
Neither has been defined in any study or by any authority. This site gives no dosing recommendations.
What results has IGF-1 LR3 produced?
Nothing published in humans, because there are no studies. In piglets daily gain increased in one of two experiments [7]C, and in cell culture the substance replaced insulin [2]D.
IGF-1 LR3 or growth hormone?
There is no direct comparative human study. Growth hormone acts at the upper end of the system and the IGF-1 analogue at the lower end [6]. There is an approved human IGF-1 product [5]; there is none of IGF-1 LR3 [1]D.
Can IGF-1 LR3 be used with growth hormone?
Not known. There is no published human study of the combination, so nothing is known about interactions.
Does IGF-1 LR3 have side effects?
None measured in humans have been published. For the substance class, hormonal and metabolic disturbances, fluid retention, muscle and joint pain and injection site reactions have been reported [6]. For the closest approved comparison, mecasermin, low blood sugar is a very common adverse reaction [12]official. Products on sale have also contained oxidised and unpurified substance [1, 4]D.
Is IGF-1 LR3 doping?
Yes. IGF-1 and its analogues are in class S2.3 of the WADA Prohibited List and are prohibited at all times [13]regulator.
IGF-1 LR3 experiences: what do studies say?
User accounts of IGF-1 LR3 have not been compiled on this site. Individual accounts are not research results, and there are no human studies of the substance. Products on sale have contained oxidised and unpurified substance [1, 4]D.
Is IGF-1 LR3 legal in Finland?
It has no marketing authorisation in Finland and has not been approved for human use [1]D. Fimea has warned against using injectable peptides bought online [11]regulator. This is not legal advice.
Read the research yourself: sources
Every source opens the original publication or the regulator's page. The level shows what the source itself reports.
- Mongongu C, Coudoré F, Domergue V, et al. Detection of LongR3-IGF-I, Des(1-3)-IGF-I, and R3-IGF-I using immunopurification and high resolution mass spectrometry for antidoping purposes. Drug Test Anal. 2021;13(7):1256-1269. PMID 33587816 D
- Bieberich E. Replacement of insulin by LongR3-IGF-1 allows for the differentiation of ES cells into neuroprogenitors and insulin-secreting cells. Anal Biochem. 2005;346(1):185-187. PMID 16169509 D
- Morris AE, Schmid J. Effects of insulin and LongR3 on serum-free Chinese hamster ovary cell cultures expressing two recombinant proteins. Biotechnol Prog. 2000;16(5):693-697. PMID 11027158 D
- Kohler M, Thomas A, Geyer H, et al. Confiscated black market products and nutritional supplements with non-approved ingredients analyzed in the Cologne Doping Control Laboratory 2009. Drug Test Anal. 2010;2(11-12):533-537. PMID 21204286 D
- Keating GM. Mecasermin. BioDrugs. 2008;22(3):177-188. PMID 18481900 (review)
- Dominikowski A, Rękoś Z, Olejarz M, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026;17:1822475. PMID 42395176 (review)
- Dunshea FR, Chung CS, Owens PC, Ballard JF, Walton PE. Insulin-like growth factor-I and analogues increase growth in artificially-reared neonatal pigs. Br J Nutr. 2002;87(6):587-593. PMID 12067429 C
- Araujo MS, Guastali MD, Paulini F, et al. Molecular and cellular effects of insulin-like growth factor-1 and LongR3-IGF-1 on in vitro maturation of bovine oocytes: comparative study. Growth Horm IGF Res. 2020;55:101357. PMID 33038561 D
- Dunaiski V, Dunshea FR, Walton PE, Goddard C. Short-term infusion of LongR3 insulin-like growth factor (IGF)-I decreases hepatic IGF-I mRNA but not IGF binding protein-3 mRNA expression in pigs. Gen Comp Endocrinol. 2002;126(2):221-228. PMID 12030778 C
- Thomas A, Walpurgis K, Thevis M. Chromatographic-mass spectrometric analysis of peptidic analytes (2-10 kDa) in doping control urine samples. J Mass Spectrom. 2024;59(1):e4996. PMID 38197510 D
- Fimea. Fimea warns: do not use injectable peptides purchased online (29 Jun 2026). Fimea regulator
- European Medicines Agency. Increlex (mecasermin) 10 mg/ml solution for injection: summary of product characteristics, section 4.8 Undesirable effects (EPAR product information). Read 14 Oct 2026. EMA official
- World Anti-Doping Agency. 2026 Prohibited List, section S2.3: "Insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues". WADA regulator
Sources read on 13 Oct 2026 and checked in PubMed on 14 Oct 2026. The mecasermin summary of product characteristics and the WADA Prohibited List read on 14 Oct 2026. Dose details are as given in the abstracts of the publications.
Evidence levels: A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed · regulator = a regulator's assessment or decision, not research evidence. The marker official means official product information (summary of product characteristics or label); it is not research evidence. For a review, the level shows what kind of research the statement rests on. No level: statements that something has not been studied, reviews' interpretations, named hypotheses and the general rules in our certificate-of-analysis guide.
Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.