IGF-1 LR3 Dosage, half-life & reference guide

Week by week.

What to expect in the first 8 weeks

Onset

1–7 days (user reports)

Peak effect

Unknown in people; the animal studies ran 7 to 14 days

Duration

3–6 weeks per community cycle

1. Day 1–14Clinical

   Low blood sugar is the thing to know first

   Commonly reported within half an hour to an hour and a half of a dose: shakiness, sweating, light-headedness or a foggy head — a blood-sugar dip, most often on an empty stomach or low carbohydrate. Eating fixes the ordinary version. A severe low, where someone is confused or cannot be roused, is an emergency rather than something to sit out.

   The science

   IGF-1 acts partly through insulin-like signaling: it drives glucose into muscle and suppresses the liver's glucose output. In pigs, the IGF-1 variants that bind the binding proteins poorly, LR3 among them, lowered glucose two to three times more potently than IGF-1 and kept it down far longer; a related variant did the same in marmosets (Tomas 1997). The human anchor is the approved IGF-1 drug rather than this analogue: in the Increlex trials low blood sugar was reported by 30 of 71 subjects at least once, five severely and four with a seizure or loss of consciousness, most often in the first month, and generally avoided by eating within about 20 minutes either side of a dose (Increlex label 2025).

   Sources

   • Tomas et al. (1997)
   • Increlex label (2025)

   Updated Oct 2026

2. Day 1–21Community

   What people notice in the first weeks

   Commonly reported early: fuller-feeling muscles and a stronger pump, especially trained fasted and fed afterwards, hunger, and easier recovery between hard sessions. Visible change is reported later and far less consistently. No study has measured any of this in people, so your own log is the only read you have.

   The science

   A 2026 review of GH- and IGF-axis compounds sold as research chemicals places IGF-1 LR3 in its lowest evidence tier — no peer-reviewed human studies, half-life not documented — and notes that the adverse effects reported in off-label use center on insulin-mimetic symptoms, which is biologically plausible given the overlap between the insulin and IGF-1 receptors (Dominikowski 2026). The cell basis for a pump-and-recovery story is real but indirect: in rat L6 myoblasts LR3 was 5 to 10 times more potent than IGF-1 at driving protein and DNA synthesis and blocking protein breakdown (Francis 1992; Ballard 1993).

   Sources

   • Dominikowski et al. (2026)
   • Francis et al. (1992)
   • Ballard et al. (1993)

   Updated Oct 2026

3. Day 14–42Animal

   What the animal studies actually showed

   The anabolic case for LR3 is rats, and it comes with two asterisks. The studies that grew body weight used a pump infusing it continuously for one to two weeks; given as injections instead it worked much less well, though it still beat plain IGF-1 on several measures. In pigs, the same infusion did the reverse.

   The science

   Tomas 1993: 14 days of continuous SubQ infusion in growing female rats, with LR3 at 44 µg/day matching plain IGF-1 at 278 µg/day for weight gain, nitrogen retention and feed-conversion efficiency; the peptides largely maintained body proportions rather than selectively adding muscle. Tomas 1996 compared infusion against once- and twice-daily injection over 7 days: injected LR3 kept an edge over injected IGF-1 on several measures, but potency was "much reduced compared with continuous infusion". Steeb 1994 and Read 1992 found the gut one of the most responsive tissues (total gut weight +43%, small intestine +47% at the top dose). Dunaiski 1997: in finisher pigs, a four-day LR3 infusion decreased average daily gain and feed intake and suppressed plasma GH, insulin, IGFBP-3 and endogenous IGF-1; in guinea pigs, LR3 raised organ weights without raising overall growth (Conlon 1995).

   Sources

   • Tomas et al. (1993)
   • Tomas et al. (1996)
   • Steeb et al. (1994)
   • Read et al. (1992)
   • Dunaiski et al. (1997)
   • Conlon et al. (1995)

   Updated Oct 2026

4. Day 21–56Animal

   The 20–30 hour half-life is not a measurement

   The number every vendor page prints comes from one unreferenced sentence in the methods of a mouse paper, and the measured animal data point the other way: LR3 clears from blood faster than IGF-1, not slower, because the binding proteins it escapes are exactly what keeps natural IGF-1 in circulation. Dosing built on a day-long half-life is built on nothing published.

   The science

   Bastian 1993 measured both in rats after IV boluses: the metabolic clearance rate was 9.84 ml/min/kg for LR3 against 0.90 for IGF-I in virgin rats (9.19 against 2.88 in pregnant rats), with most of the LR3 circulating as free peptide. Gillespie 1996 found total LR3 clearance significantly increased again in renal failure. The 20-to-30-hour figure appears, with no citation attached, in the in-vivo methods of a 2011 mouse atherosclerosis study that infused LR3 by minipump (von der Thüsen et al.), and that one sentence is what the community figure traces to. Ballard 1993 states the principle plainly: an IGF variant that associates poorly with the binding proteins is removed more rapidly from blood and is more potent.

   Sources

   • Bastian et al. (1993)
   • Gillespie et al. (1996)
   • von der Thüsen et al. (2011)
   • Ballard et al. (1993)

   Updated Oct 2026

5. Day 42+Community

   Past six weeks: nothing is mapped

   Community cycles stop between three and six weeks and take an equal break; past that, there is no animal or human data on repeated courses. The concerns that sit on the approved IGF-1 drug's label — including tumor monitoring — were written for years of use in children, not weeks in adults, but they are the only long-horizon information the class has.

   The science

   The IGF-1 receptor is a growth receptor, and the Increlex label carries post-marketing reports of malignant tumors in treated children with an instruction to monitor, noting most occurred in patients with cancer-predisposing conditions or at doses producing IGF-1 above the normal range for age; in rodents, doses above the maximum tolerated dose produced skin and mammary tumors (Increlex label 2025). Whether that translates to short adult courses of an analogue is unstudied — the 2026 review calls it a biologically plausible but unproven mitogenic concern (Dominikowski 2026). No toxicology study of IGF-1 LR3 has been published.

   Sources

   • Increlex label (2025)
   • Dominikowski et al. (2026)

   Updated Oct 2026

6. Any dayAnimal

   What IGF-1 LR3 is built on

   A real molecule with a real mechanism and no human record. It was built in 1992 as a research reagent for studying how IGF-binding proteins work. The muscle case is rat infusions from one group, contradicted in pigs. Add the product question — what is in a vial can be a tagged laboratory version, as in the one black-market vial analyzed — and the honest summary is: plausible, potent in a dish, unstudied in people.

   The science

   Francis 1992 describes its construction and the key control: in cells secreting binding proteins it was the most potent analogue tested, and in binding-protein-free chicken embryo fibroblasts it was less potent than IGF-I. Ballard 1993 quantifies the affinity drop (about 1,000-fold against IGFBP-3 and IGFBP-4) and the 5-to-10-fold potency gain in L6 myoblasts. The anabolic animal work is Tomas 1993 and Tomas 1996; the species contradiction is Dunaiski 1997. Kohler 2010 identified His-tagged Long-R3-IGF-I in a black-market injection vial and concluded the product was likely a by-product of biochemical production rather than something synthesized for injection. A 2026 clinical review places it in the lowest evidence tier, with no peer-reviewed human studies (Dominikowski 2026).

   Sources

   • Francis et al. (1992)
   • Ballard et al. (1993)
   • Tomas et al. (1993)
   • Tomas et al. (1996)
   • Dunaiski et al. (1997)
   • Kohler et al. (2010)
   • Dominikowski et al. (2026)

   Updated Oct 2026

7. With HGH and MK-677Community

   Stacked on the GH axis: the same arm twice

   The common pairing is GH or a secretagogue plus IGF-1 LR3, because one raises your own IGF-1 and the other adds more. Worth seeing clearly: both land on the same receptor pathway, and the side effects that stack are the glucose ones — GH pushes blood sugar up and insulin sensitivity down, while IGF-1 pulls sugar down, so the swings get wider, not smaller.

   The science

   GH works largely by raising IGF-1; MK-677 raised 24-hour GH and lifted IGF-1 into the young-adult range in older adults (Chapman 1996), with fasting glucose up about 5 mg/dL and reduced insulin sensitivity over two years (Nass 2008). IGF-1 itself lowers glucose and suppresses insulin secretion (Increlex label 2025). In pigs, co-administering GH with infused LR3 did not restore the growth that LR3 suppressed, and plasma insulin, IGFBP-3 and IGF-1 stayed down (Dunaiski 1997). No study has tested GH or MK-677 with IGF-1 LR3 in people.

   Sources

   • Chapman et al. (1996)
   • Nass et al. (2008)
   • Increlex label (2025)
   • Dunaiski et al. (1997)

   Updated Oct 2026

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A typical run.

Safety.

Goes with.

• HGH
• MK-677

Questions people ask.

Research.

Reference.

Cadence

Daily

Daily (community protocols: training days)

Half-life

Not measured in people: no human pharmacokinetic study of IGF-1 LR3 has been published. In rats it cleared from plasma about ten times faster than IGF-1 (Bastian 1993), because escaping the binding proteins is both what makes it potent and what lets it clear. The 20–30 hour figure repeated across community guides traces to one unreferenced sentence in the methods of a mouse atherosclerosis paper and has never been measured.

Research basis

●●● Emerging

Primarily preclinical / limited human data