IGF-1 LR3 and MGF: muscle peptides, evidence and risks

Short answer: IGF-1 LR3 and MGF are muscle-focused peptides related to insulin-like growth factor 1, the hormone that carries out much of growth hormone's effect on muscle. IGF-1 LR3 is a long-acting modified form, and MGF is a version that muscle makes after training or injury. Both show muscle growth and repair effects in cell and animal studies, but neither has been tested in human trials for muscle building. They also carry real risks, mainly low blood sugar, so they should only be used under close medical supervision and never by tested athletes.

Key facts

How does IGF-1 build muscle?

When growth hormone is released, the liver and muscles make IGF-1. IGF-1 tells muscle cells to take up amino acids and build protein, and it helps satellite cells, the muscle's repair cells, to multiply. Natural IGF-1 is quickly bound by carrier proteins and lasts only minutes in a free form.

What is different about IGF-1 LR3?

IGF-1 LR3 has one amino acid changed and 13 extra amino acids added. These changes mean carrier proteins hold on to it much less, so it stays active for many hours instead of minutes. That makes it much stronger than natural IGF-1 per dose. It was first developed as a laboratory tool to grow cells. The only approved IGF-1 medicine, mecasermin, is used in children with a rare growth disorder, not for muscle building.

What is MGF?

When a muscle is loaded or damaged, it briefly makes a special form of IGF-1 called MGF. In animal studies MGF activated satellite cells and helped repair after injury, which is why it is linked to recovery. Natural MGF breaks down within minutes, and how well injected MGF works in humans is not known.

How they compare with growth hormone peptides

Peptides such as CJC-1295 + Ipamorelin raise your own growth hormone, which then raises IGF-1 within the body's normal limits. IGF-1 LR3 and MGF bypass that control. That is why many physicians start with growth hormone releasing peptides and keep IGF-1 LR3 and MGF for specific cases. Read growth hormone peptides explained or browse the muscle and growth hormone collection.

Risks you should know

• Low blood sugar: IGF-1 acts partly like insulin. Shakiness, sweating, confusion or fainting need sugar straight away and a call to your physician.
• Cancer concern: high IGF-1 levels are linked in population studies with some cancers. People with cancer or a strong family history should avoid these peptides.
• Unknown long-term effects: there are no long-term human safety data.
• Sport: IGF-1, its analogues and MGF are on the WADA prohibited list, which the Saudi Arabian Anti-Doping Committee follows.

Who should not use them

Anyone under 18, pregnant or breastfeeding women, people with diabetes on insulin or sulfonylureas, people with active or past cancer, and athletes in tested sport.

Common questions

Is IGF-1 LR3 better than growth hormone?

It is stronger per dose on muscle cells, but less controlled and less studied in people. Most physicians prefer peptides that raise your own growth hormone first.

Does MGF help recovery after injury?

Animal studies suggest it may. For injuries, BPC-157 and TB-500 are more commonly used. See the Wolverine stack.

What is the difference between the 300 mcg vial and the 0.3 mg pen?

The dose is the same (300 mcg equals 0.3 mg). The pen is prefilled and ready to use, while the vial is the same peptide supplied in a vial and prepared by your care team.

Should I eat before an IGF-1 LR3 dose?

Your physician will advise on timing. Many plans pair it with a meal to reduce the risk of low blood sugar.

Information on this website is for education only and does not replace a physician's advice. Treatments are dispensed by prescription only, after assessment by a licensed physician.

Keep reading

• Growth hormone peptides explained
• Peptides vs steroids and SARMs
• Wolverine vs Glow vs KLOW
• Muscle and growth hormone peptides

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