What Is HGH Fragment 176-191? Dosage, Half-Life & How to Track It

What HGH Fragment 176-191 is and how it works

Full-length human growth hormone is 191 amino acids long, and it does several jobs at once — building muscle, raising blood sugar, and mobilizing fat. Researchers found that the very last stretch of the molecule, amino acids 176 through 191, is responsible for the fat-mobilizing (lipolytic) effect almost on its own, largely separable from HGH’s other actions. Isolating that fragment was the whole point: a fat-loss signal without the growth-promoting or glucose side effects that come with injecting full HGH.

Mechanistically, the fragment stimulates lipolysis (fat breakdown) and blocks lipogenesis (new fat formation) through a distinct binding interaction, rather than working through the classical GH receptor the way full HGH does. That is also why it does not meaningfully raise IGF-1 — the marker used to track full HGH dosing — and does not produce the insulin resistance or elevated blood glucose associated with GH excess.

A stabilized version of this exact fragment, AOD9604, was developed by an Australian biotech and taken through Phase IIb human obesity trials. It had a clean safety profile, but was discontinued around 2008 when it failed to separate meaningfully from placebo on weight loss — a genuinely important data point that gets left out of most research-peptide marketing for this compound.

Typical dosing & reconstitution

HGH Fragment 176-191 ships as a lyophilized powder reconstituted with bacteriostatic water, the same as most short peptides. Community protocols commonly run 250–500 mcg subcutaneously, once or twice daily, often timed fasted in the morning or before training on the theory that lipolysis is easiest to trigger when insulin is already low.

At 1.0 mg/mL, a 250 mcg dose is 25 units on a standard U-100 insulin syringe. From the more concentrated 2.5 mg/mL mix, the same dose is 10 units — worth knowing before assuming a small vial means small units. The calculator does this conversion for any vial-and-water combination.

Half-life & what it means for frequency

As an unmodified linear peptide fragment with no albumin-binding tail, HGH Fragment 176-191 clears quickly — on the order of minutes to a couple of hours — which is the basis for once- or twice-daily dosing rather than a weekly schedule. There is no depot effect to lean on between injections.

This is also where the fragment differs practically from full HGH: because it does not need to ride a pulsatile release pattern the way GH secretagogues do, timing is more about convenience — fasted state, pre-workout — than about matching a natural rhythm.

What to track & common side effects

Reported side effects are generally limited to injection-site irritation and occasional flushing or headache — a cleaner profile than full HGH, consistent with the fact that it does not touch the IGF-1 or glucose pathways that drive most GH-related side effects.

Given that the Phase IIb trial for the stabilized version did not clearly beat placebo on weight loss, the honest tracking priority is a real before/after: body weight and waist measurement on a consistent schedule, rather than assuming the mechanism guarantees the outcome.

Frequently asked questions