IGF-1 LR3

Key points

• IGF-1 LR3 is a modified form of IGF-1, a growth factor the body makes in response to growth hormone.
• The modifications make it last around a day in the body, far longer than natural IGF-1, which lasts only minutes.
• It is marketed for muscle growth and recovery, with little direct human evidence.
• It is not a licensed medicine in the UK, and growth factors are prohibited in sport.

Quick facts

What it is

Modified, long acting IGF-1 (growth factor)

Marketed for

Muscle growth and recovery

UK status

Not a licensed medicine; sold for research use

Human evidence

Very limited; marketing ahead of data

In sport

On the WADA Prohibited List

How it works

IGF-1 is the signal through which much of growth hormone's effect is carried out, telling cells to grow and divide and helping muscle take up nutrients. IGF-1 LR3 is engineered to resist the proteins that normally rein IGF-1 in, so it stays active far longer. That longer action is exactly what makes it attractive for muscle building and what makes its effects harder to control.

What the evidence shows

There is very little direct human evidence for IGF-1 LR3 as used in sport and bodybuilding. The science of IGF-1 itself is well understood, but that does not establish that injecting a long acting version is safe or effective for building muscle. The marketing claims run well ahead of any controlled human data.

What it does not settle

• There are no proper human trials of IGF-1 LR3 for muscle or performance.
• Long term safety is unknown, and products are not quality assessed.
• The right dose, if any, has never been established in trials.

Side effects

Common

• Because it acts on blood sugar much as insulin does, it can cause low blood sugar, with shakiness, sweating and confusion.
• Injection site reactions and fluid retention are also reported.

Less common but serious

• Severe low blood sugar can be dangerous. IGF-1 also drives cell growth, so there is a real theoretical concern about encouraging the growth of cancers.
• Because there is no licensed product, the dose, purity and contents of material bought online cannot be verified.

Report any suspected side effect through the MHRA Yellow Card scheme.

UK legal status and access

IGF-1 LR3 has no UK marketing authorisation, so it is not a licensed medicine and is not offered by registered clinics or pharmacies. It is sold online labelled for research use. Injecting a potent growth factor of unknown quality carries serious risks.

Common questions