Insulin Lispro (Humalog)
Insulin lispro is a rapid-acting recombinant human insulin analogue (brand Humalog) with onset in ~15 minutes. Bodybuilders use it post-workout or around meals to drive glucose, amino acids and creatine into muscle. Its speed makes hypoglycaemia fast and potentially fatal, making it one of the most dangerous drugs in physique circles.
01 Overview
Lispro reverses the proline-lysine sequence at positions B28-B29, which prevents hexamer self-association and gives faster subcutaneous absorption than regular insulin. It is a genuine, extensively studied prescription drug for type 1 and type 2 diabetes.
In bodybuilding it is dosed around carbohydrate feeding to exploit its anabolic and nutrient-partitioning action. The margin for error is very small: a few extra units, a missed meal, or post-exercise insulin sensitivity can produce severe neuroglycopenia, seizure, coma or death within an hour. Unlike anabolic steroids, an insulin mistake can kill on the day it is made.
02 Mechanism
Binds the insulin receptor, triggering GLUT4 translocation and glucose uptake into muscle and fat, activating glycogen and protein synthesis via PI3K/Akt/mTOR and suppressing lipolysis and hepatic gluconeogenesis. The rapid analogue kinetics concentrate this effect in the 1-3 hours after injection.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Beginner (off-label) | 1–5 IU | SubQ | Post-workout with ~10 g carbs per IU; extreme caution |
| Diabetic bolus | 4–20 IU | SubQ | Individualised to carbohydrate and glucose; medical use only |
| Common (off-label) | 5–10 IU | SubQ | Higher units sharply raise hypoglycaemia risk |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Enhanced glycogen and nutrient storageDrives glucose and amino acids into muscle, supercompensating glycogen. | Fuller muscle bellies, larger pumps | Clinical | |
| Anti-catabolic / anabolic signallingActivates mTOR and suppresses protein breakdown, supporting muscle protein balance. | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Fat gain and lipohypertrophyAdipose accumulation, especially with excess calories, and fatty lumps at injection sites. | Mild | Common | Clinical | |
| Severe hypoglycaemiaBlood glucose crashes causing sweating, confusion, seizure, coma and death; rapid onset with lispro. | Life-threatening | Common in misuse | Clinical |
06 Commonly used with
What insulin is combined with, and why. This is about intent rather than safety — the interactions table below covers what is dangerous. Nothing here is listed without what it costs.
| Compound | Frequency | Purpose & trade-off |
|---|---|---|
| Stacked compounds | ||
| Growth HormoneGH/slin | Paired with GH in advanced mass protocols to counter GH-induced insulin resistance and drive nutrients into muscle.Trade-off: Combining the two magnifies hypoglycaemia risk, which can be life-threatening without precise carb timing. | |
| Testosteronemass base | Run as the anabolic base so the extra nutrient uptake insulin provides is partitioned toward muscle growth.Trade-off: Insulin promotes fat gain if calories overshoot, and the hypoglycaemia danger remains ever-present. | |
| IGF-1 LR3advanced protocol | Layered with IGF-1 for additive nutrient partitioning and muscle-cell growth in high-level bulking.Trade-off: Both lower blood glucose, so their combined hypoglycaemic effect is severe and easy to underestimate. | |
| Support & ancillaries | ||
| Metforminsensitivity support | Sometimes used around insulin protocols to preserve insulin sensitivity over the longer term.Trade-off: Metformin causes GI upset and does not remove the acute hypoglycaemia risk that makes insulin use dangerous. | |