Medical review of IGF-1 LR3

By Dr. Dimitar Marinov

medical reviewed by Best HGH Doctors and Clinics dedicated team.

Evidence basedThis article is reviewed by medical professionals for the relevancy and accuracy of the content. Every article is evidence-based and contains references to peer-reviewed studies and academic research.

Peptides are some of the most popular performance-enhancing drugs amongst athletes and bodybuilders due to their anabolic and fat-burning properties.

However, most of these products are illegal for use because their safety and effectiveness are poorly researched.

One such peptide is LR3 IGF-1, also known as “Long R3 IGF-1”. It is an analog of the insulin-like growth factor 1 (IGF-1), which is naturally found in the human body, and its primary function is to mediate the anabolic effects of the growth hormone (HGH).

Long R3 IGF-1 is modified to help increase its potency and stability while still exerting anabolic effects similar to IGF-1

“Long” stands for the additional 13 amino acids added to the N-terminus of the IGF-1 molecule, while “R3” describes the replacement of the 3rd amino acid in IGF-1 with arginine.

Athletes and bodybuilders use it illegally because of promises of increased muscle mass, strength, and physical performance.

However, IGF-1 LR3 was never intended for human use, and clinical research regarding its effects or safety is lacking. Due to these safety concerns and the uncertain results, it is best to abstain from taking poorly studied products such as LR3 IGF-1.

In this article, you will discover more about the research regarding Long R3 IGF-1 and whether the risk of side effects is worth any potential benefit.

What is IGF-1 LR3?

IGF-1 and its analogs such as Long R3 IGF-1, des(1-3)IGF-1 and R3-IGF-I, have mitogenic effects, which speed up cell replication in different tissues.

IGF-1 LR3 Half-life and Difference

IGF-1 LR3 was developed to improve the stability and efficiency of IGF-1 for stimulating cell growth in in vitro experiments. Adding IGF-1 LR3 to cell culture speeds up cell division, which shortens the time to conduct laboratory studies.

IGF-1 LR3 achieves this by activating the IGF-1 receptors found in most human and animal cells. Activating these anabolic receptors also stimulates protein synthesis and tissue growth.

Difference between IGF-1 and IGF-1 LR3

Most of the IGF-1 naturally found in your body binds to serum proteins called IGF-1 binding proteins. This prolongs its half-life by up to 15 hours but reduces the affinity to the IGF-1 receptors.

In comparison, the IGF-1 LR3 analog appears to have a higher affinity to the anabolic IGF-1 receptors and binds less to serum proteins.

As a result, IGF-1 LR3 has enhanced potency, and animal studies report that continuous infusion with LR3 IGF-1 had up to 2-fold higher anabolic effects than IGF-1. Tested animals experienced higher weight gain and an increase in the weight of some of their organs.

The half-life of IGF-1 LR3

Currently, there is no clinical evidence reporting its half-life in the human body, but the common beliefs you may find on the Internet that it is longer than that of IGF-1 (up to 20-30 hours) appear to be unsubstantiated.

In fact, LR3 IGF-1 is most likely eliminated quite fast in the human body due to the fact that it binds less to serum proteins such as IGF-1 binding protein.

What is more, studies in mice report that IGF-1 LR3 is eliminated entirely within 4 hours of intramuscular injection, meaning its half-life in mice is less than 1 hour. The metabolites of IGF-1 LR3 had a slightly longer half-life and were detectable for up to 16 hours after the injection.

In terms of effects, animal research reveals that administering IGF-1 LR3 helps protect against muscle mass loss and catabolism during reduced periods of energy intake. The peptide was infused for 8 hours, significantly suppressing the natural IGF-1 production.

Yet, there is no clinical research reporting on its effects on humans, so there is no guarantee it will work the same way. IGF-1 LR3 is also not meant for human use and can be legally obtained only for research purposes.

Is IGF-1 LR3 better than HGH?

Athletes and bodybuilders purchase the product on the black market, hoping it will provide similar or greater benefits than taking IGF-1 or HGH.

Compared to IGF-1 LR3, HGH therapy has been studied much more extensively, and a considerable amount of evidence supports its effectiveness.

Furthermore, HGH promotes anabolic effects in muscle tissue while also stimulating fat breakdown. IGF-1 and its analogs are capable of mediating only the anabolic effects of HGH.

HGH therapy also has well-known side effects, which can be easily avoided by correcting the dose of the medication. In comparison, IGF-1 LR3 is not studied in humans, and there is a risk of unexpected side effects.


LR3 IGF-1 is available as a sterile filtered white lyophilized (freeze-dried) powder that must be reconstituted with distilled water and used for research purposes only. The vial sizes range from 0.2 to 1 mg.

IGF-1 LR3 dosage and mixing

For research purposes, the vial must be reconstituted with 2-10 ml of sterile water until achieving a concentration of 0.1 mg per milliliter. Afterward, the solution should be stored in a refrigerator at 4°C for 2-7 days.

Nevertheless, athletes and bodybuilders often purchase the product illegally and administer it subcutaneously. According to unofficial sources, the most common dosage when used as a performance-enhancing drug ranges from 0.2 to 1 mg per day.

These doses are much lower compared to the officially recommended doses for unmodified IGF-1, which is also available as a medication for patients with IGF-1 deficiency.

These patients take 0.04–0.12 mg/kg of IGF-1 twice daily subcutaneously, which is equal to at least 5.6 mg of IGF-1 per day for a 70 kg person.

Despite the fact that IGF-1 LR3 is an analog with 2-3 times higher potency and purportedly longer half-life, it is unlikely that taking it in doses more than ten times lower than IGF-1 may provide any noticeable effects.

How to administer IGF-1 LR3

Due to the lack of data from clinical research and the fact that IGF-1 LR3 is not approved for human use, there are no official recommendations on how and where to inject it.

Considering that the peptide is an analog of IGF-1, athletes and bodybuilders use it in a similar fashion, mainly by injecting it subcutaneously once or twice a day.

IGF-1 and its analogs are most bioavailable when injected because they are not reliably absorbed through the digestive system or skin.

Where to inject

The subcutaneous route is generally considered the preferred method for administering peptides such as IGF-1 because it provides slower release and increased half-life of the medication compared to injecting them intramuscularly.

Most individuals who abuse IGF-1 LR3 as a performance-enhancing drug take it once a day for 4 to 6 weeks, usually right before or after a workout, and then cycle it off. However, there is no research to substantiate such a dosing regime.

What results you can expect?

It is unclear how long it may take until there are any benefits of IGF-1 LR3 when used in humans.

What are the benefits of IGF-1 LR3?

According to animal research, the benefits of IGF-1 LR3 are limited, because IGF-1 and its analogs possess only the anabolic effects and lack the fat-burning properties of growth hormone.

However, the Internet is filled with claims that LR3 IGF-1 can cause unique and proven benefits such as:

  • major muscle gains
  • improved communication between the cells
  • better physical performance
  • faster metabolism
  • fat loss
  • better recovery from injuries
  • faster healing
  • improved cognition


The only plausible benefits supported by any research are those observed in test animals, including reduced muscle damage during activity, muscle-sparing effects, increased organ growth, and weight gain.

Moreover, some in vivo studies show that the peptide may actually reduce growth in tested animals due to the suppressive effect of LR3 IGF-1 on the natural HGH synthesis.

Therefore, the research regarding the effects of LR3 IGF-1 remains preliminary and mostly controversial.

What are the side effects?

A prominent and potentially life-threatening side effect of taking IGF-1 LR3 is hypoglycemia. Hypoglycemia is a term that describes dangerously low blood sugar, which manifests with shaking, sweating, dizziness, hunger, confusion, and loss of consciousness.

It occurs due to the similarity between insulin and IGF-1 or IGF-1 analogs, as they all trigger the insulin receptors and stimulate glucose uptake inside body cells. This leads to a drop in blood sugar levels and hypoglycemia.

Studies also report that IGF-1 LR3 may lead to the growth of mucosa inside the intestines. This effect occurs mainly due to an increase in the number of mucosal cells in the small intestine.

As a result, IGF-1 LR3 may, at least in theory, lead to an enlargement of the intestines and “bubble gut,” similar to those observed in bodybuilders who abuse HGH.

Currently, there is not enough evidence to report more potential side effects of IGF-1 LR3. It is unclear whether the peptide may affect insulin resistance, water retention, or other factors which are usually related to HGH abuse.

Considering the similarities between IGF-1 and IGF-1 LR3, you may expect similar effects and side effects for this analog. For example, studies on IGF-1 report that it is not associated with increased insulin resistance.

Unfortunately, IGF-1 LR3 may lead to other side effects similar to those related to IGF-1, like stimulating the growth of existing tumors, acromegaly, and organ enlargement.