Is IGF-1 LR3 measured in IU?
Short answer: no. IGF-1 LR3 is not measured in IU. It is measured by mass — in micrograms (mcg) and milligrams (mg). A microgram is one-thousandth of a milligram, and a milligram is one-thousandth of a gram. They are simply tiny weights, the same way you might weigh a grain of salt.
IU stands for "international unit." An IU is not a weight at all. It is a measure of how much a substance does — its biological activity — and it is set by an official reference standard for that one specific substance. Because of that, an IU of one thing and an IU of another thing are completely different amounts. There is no IU for IGF-1 LR3, so there is no honest way to write its amount "in IU."
So if you have seen a number written as "IGF-1 LR3 dosage in IU," that number does not really mean anything. It is a sign of a common mix-up, not a real way the compound is measured. The rest of this page explains where the mix-up comes from — and, much more importantly, why there is no approved dose to convert in the first place.
What is an international unit, exactly?
It helps to slow down on what an "international unit" really is, because the word "unit" makes it sound like a fixed, standard size — like a teaspoon or a single tablet. It is not either of those.
An international unit measures the effect of a substance, not its weight. For a handful of biological substances — certain hormones, vitamins, and vaccines — the world's health bodies keep an official physical reference sample and declare, "this much activity equals one IU." Every batch of that substance is then compared back to that reference. The whole point of the system was historically practical: in the early days, makers could not purify these substances well enough to trust their weight, so they measured what the substance did instead.
Two consequences follow, and both matter here. First, an IU only exists for a substance that someone has bothered to define a standard for — there is no universal conversion between IU and milligrams that works across different substances, because each IU is defined separately. Second, a substance that can be made and weighed precisely usually does not need an IU at all; it is simply measured by mass. IGF-1 LR3 falls into that second bucket. It is weighed, not activity-rated, so "IGF-1 LR3 in IU" is asking for a number that was never created.
A concrete picture makes the "no universal conversion" point obvious. The mass behind one IU is different for every substance: one IU of insulin and one IU of, say, vitamin D correspond to wildly different physical weights, because each was pinned to its own separate reference. So even when a real IU exists, you cannot take a milligram amount of one substance, look up someone else's "mcg per IU," and get a meaningful answer — the conversion only ever applies to the exact substance it was defined for. For a compound like IGF-1 LR3 that has no IU at all, there is simply nothing on the other side of the equals sign. Any "X mcg = Y IU" table you find for it has been made up.
| Concept | What it means |
|---|---|
| International unit (IU) | A measure of biological activity vs. an official reference standard for one substance — not a weight |
| Milligram (mg) | A unit of mass; one-thousandth of a gram |
| Microgram (mcg) | A unit of mass; one-thousandth of a milligram (1000 mcg = 1 mg) |
| How IGF-1 LR3 is measured | By mass (mcg/mg); it has no IU standard, so "IGF-1 LR3 in IU" is not a real measurement |
| How insulin is measured | In units — standard insulin is U-100 (100 units per mL) |
| IU-to-mg conversion | No universal conversion exists; each IU is defined separately per substance |
Why do people confuse it with IU?
The confusion is easy to understand. Two of the most famous injectable hormones really are measured in units: insulin and growth hormone (often called HGH). If you have ever seen someone with diabetes draw up insulin, the syringe is marked in "units," not in milligrams.
Insulin is a clear example. The standard insulin sold in the United States is "U-100," which means there are 100 units of insulin in every milliliter of liquid — a fact printed right on the label. People count insulin in units every single day. Growth hormone has historically been talked about in international units too. So when someone hears about another injectable peptide, their brain reaches for the unit it already knows: IU.
But "measured in units" is not a rule for all peptides — it is a special case for a few specific hormones that happen to have an official unit standard. Most peptides, including IGF-1 LR3, are simply weighed. Reaching for IU here is like asking how many "cups" a bag of flour weighs: cups measure volume, grams measure weight, and the question quietly mixes up two different kinds of measurement.
Here is the detail that settles it cleanly. There is an FDA-approved medicine made from native IGF-1 — the natural version of this hormone. It is called mecasermin (brand name Increlex), and it is approved only for a rare growth disorder in children. On its official label, the dose is written in milligrams per kilogram of body weight — for instance a starting range of 0.04 to 0.08 mg/kg twice daily. It is never written in IU. Even the real, approved IGF-1 medicine is measured by weight, not in units.
What is IGF-1 LR3, and is there an approved dose?
IGF-1 LR3 is a man-made, slightly changed copy of a natural body hormone called insulin-like growth factor 1 (IGF-1). The "LR3" part refers to two small tweaks to its structure. Those tweaks make it slip past certain blood proteins that normally grab and hold onto natural IGF-1, so in laboratory studies more of it stays in an active form. In animal research the analogue was actually cleared from the blood faster than ordinary IGF-1 but still acted more potently (PMID 8708565). That difference has been studied in animals and in the test tube, not as an approved treatment.
Now the part that matters most: there is no approved dose for IGF-1 LR3. None. It is not an FDA-approved medicine for any use in people. It is sold as a "research chemical," usually labeled "research use only" or "not for human use." That label is not a formality — it means no health authority has reviewed it as a treatment, and there are no human dosing guidelines for it anywhere.
Because no regulator has approved it, several safety nets that normal medicines have simply do not exist for IGF-1 LR3. There is no checked standard for how pure or correctly made each batch is. There is no tested, official dose from controlled human trials. And there is no system tracking side effects in people who use it. It is also banned in sport — exogenous IGF-1 and its analogues are on the World Anti-Doping Agency Prohibited List, banned at all times, in and out of competition.
So when someone asks "what is the IGF-1 LR3 dosage in IU," the truthful answer has two parts. First, it is not measured in IU — it is measured by mass. Second, and more importantly, there is no approved dose in any unit, because it is not an approved medicine. The question skips over the bigger issue.
Why unit confusion is dangerous here
With an everyday medicine, getting the units wrong is already a serious problem. With an unregulated research chemical, it is worse, and here is the plain reason: there is no safety net to catch the mistake.
Think about how far apart these units are. Insulin units, milligrams, and micrograms are not close to each other. If a person assumes a research peptide works "like insulin units" and measures it that way, they can be off by a huge multiple without realizing it. There is no pharmacist double-checking, no standard package insert to compare against, and often no reliable way to even know how concentrated the product in front of them actually is.
That last point is not theoretical. When researchers chemically tested injectable peptide products bought online without a prescription, they found the labels could not be trusted: one 2024 analysis of grey-market semaglutide measured purity as low as 7.7% to 14.37% against a claimed 99%, with bacterial endotoxin — a contaminant that can cause fevers and worse — in every single sample (PMC11582493). It is a different peptide, but it comes from the same unregulated supply, and it shows how unreliable "what is actually in the vial" can be. Stacking a units guess on top of an unknown concentration is guessing on top of guessing.
Mixing up micrograms and milligrams alone is a thousand-fold difference — the gap between a grain and a thousand grains. Add an imagined "IU" into the mix and the numbers become pure guesswork. And this is a hormone that pushes cells to grow: in large studies, people with naturally higher IGF-1 have shown a modestly higher risk of some cancers, such as prostate and premenopausal breast cancer (PMID 15110491) — an association, not proof of cause, but reason enough not to treat over-dosing this signal casually. This is exactly why the honest takeaway is not "here is the right conversion." There is no safe conversion to give, because there is no approved dose and no quality-controlled product to apply it to.
Who to actually ask
If you are trying to understand IGF-1 — whether your own IGF-1 level is normal, or whether anything that acts on this hormone could be relevant to you — the right person to ask is a licensed clinician. A doctor can order the proper blood test, read it against the correct range for your age and sex, and explain what it means for you specifically. That is something no article and no online dose chart can do.
A clinician can also give you the straight story on research chemicals like IGF-1 LR3: why they are not approved, what is and is not known about them, and what the genuine risks are. They can put your actual question — usually some version of "is my growth-hormone system normal?" — into a framework that uses validated tests and real reference ranges, instead of a made-up unit. That is a very different and far more useful conversation than hunting for a dose in the wrong units.
This article is information, not medical advice, and it is not a guide for using IGF-1 LR3. PeptidePanel does not sell, supply, or recommend IGF-1 LR3 or any compound. Any decision about a substance that acts on the growth-hormone system belongs with a licensed clinician who knows your full health history.
Keeping track of a clinician-set plan with PeptidePanel
If a licensed clinician does set you up with a prescribed, approved treatment, the day-to-day tracking can get fiddly fast: what was taken, how much, when, and how your follow-up lab numbers are trending over time. That is easy to lose track of in your head or scattered across notes.
PeptidePanel is a simple tracking tool for exactly that. It records the plan your clinician set — including the dose in the real units your clinician wrote it in — charts your results over time, and reminds you when something is due. It does not sell, supply, or recommend any compound, and it is not a dose calculator. It is just the organized notebook that keeps your clinician's plan in one place.