HGH Frag 176-191, also called Fragment 176-191 or HGH Frag, is a synthetic copy of the last 16 amino acids of human growth hormone. That end of the hormone seemed to carry growth hormone's fat-burning effect, so researchers in Australia studied it as an obesity treatment.
Frag 176-191 itself has never been tested in people. The human trials were all done with a close relative, AOD-9604, and the biggest one failed. Frag 176-191 is sold online as a research chemical for fat loss.
- Frag 176-191 is the C-terminal 16 amino acids of human growth hormone.
- It's not the same as AOD-9604, which adds a tyrosine to amino acids 177 to 191. All human trials used AOD-9604.
- In obese mice and rats, related fragments slowed weight gain and reduced fat. In people, AOD-9604 failed a 502-person weight loss trial.
- AOD-9604 doesn't bind the growth hormone receptor, so Frag 176-191 isn't expected to act like growth hormone. That hasn't been tested directly.
- WADA bans hGH 176-191 by name. It isn't FDA approved.
- Online users report 200 to 500 mcg a day. No dose has been tested in people.
| What it is | Growth hormone amino acids 176 to 191 (FLRIVQCRSVEGSCGF) |
| Molecular weight | About 1,799 g/mol |
| Common vials | 2 mg, 5 mg, 10 mg |
| Route | Injection under the skin (online use) |
| Human studies | None (the human trials used AOD-9604) |
| FDA status | Not approved; sold for research use only |
| In sport | Prohibited at all times, named in WADA S2 |
What Is HGH Frag 176-191?
Growth hormone is a 191-amino-acid protein. In the 1970s and 1990s, Frank Ng's lab at Monash University in Melbourne made short pieces of its tail end and tested them in rats. One piece, amino acids 177 to 191, blocked fat storage in rat fat tissue as well as the whole hormone did.[1] Frag 176-191 is that tail plus one more amino acid, phenylalanine, at position 176.
AOD-9604, a close relative, doesn't compete for the growth hormone receptor and doesn't make cells multiply the way growth hormone does.[2] That's why this part of the hormone was studied as a fat-loss drug without growth hormone's other effects. Frag 176-191 itself hasn't been tested this way.
Frag 176-191 vs AOD-9604
| Frag 176-191 | AOD-9604 | |
|---|---|---|
| Sequence | Growth hormone 176 to 191, starting with phenylalanine | Growth hormone 177 to 191 with an extra tyrosine at the front[3] |
| Molecular weight | About 1,799 | About 1,815 |
| CAS number | 66004-57-7 | 221231-10-3 |
| Human trials | None | Six trials in 893 people, 2001 to 2006[4] |
The two molecules differ by one atom of oxygen, but they're different compounds, and the human data belong only to AOD-9604. Some sellers list AOD-9604's sequence, formula or CAS number on their Frag 176-191, so check your label. Our AOD-9604 page covers that compound in detail.
How HGH Frag 176-191 Works
The Ng lab and its collaborators proposed that this part of growth hormone works on fat in two ways:
- Less fat storage. In rat fat tissue, the 177-191 fragment blocked the making of new fat. In that early study it didn't speed fat breakdown.[1]
- More fat burning. In obese mice, growth hormone and AOD-9604 increased fat breakdown and raised activity of the gene for the beta-3 adrenergic receptor, a fat-burning switch. In mice without that receptor, long-term treatment no longer changed body weight, but AOD-9604 still raised energy use in a short test. The authors concluded the fat-burning effect doesn't run directly through that receptor.[5]
These are animal studies of related fragments. How much of this applies to Frag 176-191 in people is unknown.
What People Use HGH Frag 176-191 For
- Fat loss. By far the main reason. Animal studies of related fragments support it; the one large human trial of AOD-9604 didn't.
- Cutting while keeping muscle. Popular with bodybuilders. There's no evidence it builds or protects muscle.
- Joint and cartilage repair. Some sellers cite a rabbit knee study, but it used AOD-9604, not Frag 176-191.[6]
The Research Behind HGH Frag 176-191
| Study | Model | What they found |
|---|---|---|
| Ng and Bornstein, 1978[7] | Rats, one injection | 176-191 and similar fragments briefly raised blood sugar and caused a longer rise in insulin |
| Wu and Ng, 1993[1] | Rat fat tissue | 177-191 blocked fat storage as well as whole growth hormone |
| Ng, 2000[8] | Obese rats, AOD-9604 by mouth, 19 days | Weight gain cut by more than half; no harm to insulin sensitivity |
| Heffernan, 2001[2] | Obese mice, 14 days | Less weight gain and more fat burning with growth hormone or AOD-9604 |
| AOD-9604 OPTIONS trial, 2007[9] | 502 obese adults, 24 weeks | No significant weight loss vs placebo; obesity program ended |
Most of the animal work didn't use Frag 176-191. The Ng lab tested 177-191, a version called AOD9401 and AOD-9604.[1][8] The only one of these papers that tested 176-191 directly is the 1978 rat study, and it found a short-lived rise in blood sugar.[7]
The human trial that failed. Metabolic Pharmaceuticals ran six AOD-9604 trials in about 900 people. In the final one, 502 obese adults took 0.25 to 1 mg by mouth daily for 24 weeks. It didn't produce significant weight loss compared with placebo, and in February 2007 the company ended its development as an obesity drug.[9] Frag 176-191 has never had a human trial of its own.
Is HGH Frag 176-191 Legal?
Frag 176-191 isn't FDA approved for any use, and it isn't a legal dietary supplement. It's sold online as a research chemical labeled not for human use.
FDA doesn't name Frag 176-191 on its compounding lists, but it does name its closest relative. In December 2024, an FDA advisory committee voted 12 to 0 against adding AOD-9604 to the list of substances compounding pharmacies can use,[10] and FDA's safety-risks page lists AOD-9604, whose nomination has since been withdrawn, as possibly posing a significant risk of immune reactions for some routes of use.[11]
In sports, it's banned by name. The WADA Prohibited List bans "growth hormone fragments, e.g. AOD-9604 and hGH 176-191" under section S2.2.3, at all times.[12]
If you want medical weight loss, proven options exist. You can find a peptide clinic near you.
HGH Frag 176-191 Dosage
No tested human dose
Frag 176-191 has never been tested in people, so there is no proven dose. The numbers below come from online users and sellers. Talk to a licensed clinician before you inject anything.
What users report: 200 to 500 mcg a day under the skin, often on an empty stomach. A common plan is 200 to 250 mcg in the morning and the same before a workout. Cycles usually run 4 to 12 weeks.
What the AOD-9604 trials used: 0.25 to 1 mg a day by mouth in the final trial.[9] That's a different compound taken a different way, so it isn't a guide for Frag 176-191 injections.
HGH Frag 176-191 dosage chart (5 mg vial)
| Dose | Units with 2 mL BAC water | Units with 1 mL BAC water |
|---|---|---|
| 200 mcg | 8 units | 4 units |
| 250 mcg | 10 units | 5 units |
| 500 mcg | 20 units | 10 units |
With 2 mL of bacteriostatic (BAC) water, each unit on a U-100 insulin syringe holds 25 mcg. At 500 mcg a day, a 5 mg vial lasts 10 days. For a 2 mg vial mixed with 1 mL, each unit holds 20 mcg, so 250 mcg is 12.5 units. Use our peptide calculator for other sizes, and the reconstitution guide for mixing steps.
HGH Frag 176-191 Side Effects
There are no human safety data for Frag 176-191.
What the AOD-9604 trials found: AOD-9604 was well tolerated, with side effects at rates similar to placebo, except at the highest dose tested (54 mg), which caused more headaches and diarrhea. The most common side effects were headache, diarrhea and other stomach upset, colds and back pain. It didn't change IGF-1 levels or blood sugar control, and no antibodies were found in the participants tested for them.[4] Those findings are for AOD-9604, not Frag 176-191.
What users report: redness or irritation where they inject, and sometimes tiredness or headache. These reports are unverified.
The bigger unknowns:
- Blood sugar. The one study that tested 176-191 directly found it briefly raised blood sugar and lowered insulin sensitivity in rats.[7] If you have diabetes or prediabetes, that matters.
- Product identity. Sellers mix up Frag 176-191 and AOD-9604, and research peptides aren't made to drug standards.
- Long-term safety. No one has followed Frag 176-191 users over time.
Who should avoid it: anyone with diabetes or prediabetes, anyone pregnant or breastfeeding, anyone under 18 and athletes who are drug tested.
Frequently Asked Questions
What is HGH Frag 176-191? A synthetic copy of the last 16 amino acids of growth hormone, sold for fat loss and never tested in people.
Is HGH Frag 176-191 the same as AOD-9604? No. AOD-9604 adds a tyrosine to amino acids 177 to 191. The human trials used AOD-9604.
Does HGH Frag 176-191 burn fat? Related fragments reduced fat in obese mice and rats. AOD-9604 failed its large human trial.
What is the HGH Frag 176-191 dose? No dose has been tested. Users report 200 to 500 mcg a day under the skin.
How many units is 250 mcg of Frag 176-191? With a 5 mg vial and 2 mL of BAC water, 250 mcg is 10 units.
Does Frag 176-191 raise IGF-1 or blood sugar? AOD-9604 didn't in human trials. A rat study found 176-191 briefly raised blood sugar.
Does HGH Frag 176-191 build muscle? There's no evidence it does. Its relative AOD-9604 doesn't bind the growth hormone receptor.
What are the side effects of HGH Frag 176-191? No human data exist. AOD-9604 trials reported headache, stomach upset, colds and back pain.
Is HGH Frag 176-191 legal? It's sold as a research chemical. It's not FDA approved or a legal supplement.
Is HGH Frag 176-191 banned by WADA? Yes. WADA names hGH 176-191 as a banned growth hormone fragment.
References
- Wu Z, Ng FM. Antilipogenic action of synthetic C-terminal sequence 177-191 of human growth hormone. Biochem Mol Biol Int. 1993;30(1):187-196. PMID: 8358331
- Heffernan MA, Thorburn AW, Fam B, et al. Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment. Int J Obes Relat Metab Disord. 2001;25(10):1442-1449. PMID: 11673763
- Cox HD, Smeal SJ, Hughes CM, Cox JE, Eichner D. Detection and in vitro metabolism of AOD9604. Drug Test Anal. 2015;7(1):31-38. PMID: 25208511
- Stier H, Vos E, Kenley D. Safety and tolerability of the hexadecapeptide AOD9604 in humans. J Endocrinol Metab. 2013;3(1-2):7-15. doi.org
- Heffernan M, Summers RJ, Thorburn A, et al. The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice. Endocrinology. 2001;142(12):5182-5189. PMID: 11713213
- Kwon DR, Park GY. Effect of intra-articular injection of AOD9604 with or without hyaluronic acid in rabbit osteoarthritis model. Ann Clin Lab Sci. 2015;45(4):426-432. PMID: 26275694
- Ng FM, Bornstein J. Hyperglycemic action of synthetic C-terminal fragments of human growth hormone. Am J Physiol. 1978;234(5):E521-E526. PMID: 645904
- Ng FM, Sun J, Sharma L, et al. Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Horm Res. 2000;53(6):274-278. PMID: 11146367
- U.S. Food and Drug Administration. AOD-9604: Pharmacy Compounding Advisory Committee briefing document. 2024. fda.gov
- U.S. Food and Drug Administration. Pharmacy Compounding Advisory Committee, December 4, 2024: final summary minutes. fda.gov
- U.S. Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks. fda.gov
- World Anti-Doping Agency. The 2026 Prohibited List, section S2. wada-ama.org
This information is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting any peptide therapy. Regulatory status may change.
