Growth hormone is well-established in general endocrinology as having an anti-insulin effect, meaning it is „insulin-antagonistic”, on the body. This means that CJC-1295 and ipamorelin, both of which increase growth hormone levels, could possibly affect blood sugar regulation. However, there is no dedicated human study measuring insulin sensitivity or blood glucose specifically in individuals using these two peptides. This therefore remains a theoretical concern grounded in robust general physiology, rather than a directly proven finding.
Do CJC-1295 and ipamorelin affect insulin sensitivity?
The relationship between growth hormone and insulin is one of the more well-documented aspects of general endocrine physiology. Growth hormone acts, in part, by counteracting some of insulin's effects on cells. This is a normal part of how the body balances energy use and storage. However, it also means that sustained periods of elevated growth hormone can decrease the efficiency with which insulin lowers blood sugar. This is a phenomenon well recognised in states of chronic growth hormone excess, such as acromegaly, and in some patients receiving growth hormone replacement therapy.
Since both CJC-1295 and ipamorelin are specifically designed to raise growth hormone secretion, it is a reasonable, mechanistically justified expectation that they might have some impact on insulin sensitivity or blood glucose regulation. This concern is mirrored in a 2026 review on performance-enhancing peptides acting on the growth hormone–IGF-1 axis. This review listed dysglycemia – abnormal blood sugar regulation – among the endocrinological and metabolic disturbances associated with this category of compounds, including specifically CJC-1295 and ipamorelin [1].
It is important to note that this review described a pattern of reported concerns at the category level and did not present data from a controlled study directly measuring fasting glucose, HbA1c, or insulin sensitivity before and after administration of CJC-1295 or ipamorelin in a specific group of individuals. No such dedicated glucose-focused clinical study was identified in the literature reviewed for this article.
Specifically concerning its use in individuals with diabetes, no published studies address the safety or effects of these peptides in the diabetic population. Given the likely mechanism described above, this represents a significant unknown rather than something that can be answered reassuringly or dismissively. Any individual with diabetes or concerns about blood sugar considering these compounds would be relying on a lack of evidence, not evidence of safety.
The effects of CJC-1295 and ipamorelin on cortisol
Cortisol is a stress-related hormone that some older growth hormone-releasing peptides are known to elevate as an unwanted side effect. One of the most notable and well-documented characteristics of ipamorelin, dating back to its original pharmacological characterisation, is that it was specifically designed and demonstrated to not significantly raise cortisol. In foundational human and animal studies of ipamorelin, researchers directly compared it to other growth hormone-releasing peptides such as GHRP-6 and GHRP-2. They found that while these older compounds elevated plasma ACTH – the pituitary hormone that triggers cortisol release – and cortisol itself, ipamorelin did not induce significant increases in either. This held true even at doses over 200 times higher than what is needed to trigger growth hormone release [2].
This selectivity is considered one of the defining pharmacological characteristics of ipamorelin. It is the reason why ipamorelin is often described in research literature as being more „selective” for the growth hormone pathway, compared to earlier generation growth hormone-releasing peptides.
For CJC-1295, the main human study did not report a detailed cortisol analysis as part of its published results. Consequently, direct human data on the effect of CJC-1295 on cortisol is not available in the literature reviewed here. It is worth noting, however, that as a GHRH analogue acting via a different receptor system than the ACTH-releasing pathway, there is no obvious mechanistic reason to expect it to elevate cortisol in the way older GHRP-type compounds did.
It is worth being precise, however, that the well-documented discovery of low cortisol described above originates specifically from ipamorelin's own basal research [2] – and not from the study of CJC-1295 or both compounds together.
Metabolic benefits of CJC-1295 and ipamorelin
Apart from the questions discussed above regarding insulin and cortisol, broader claims that CJC-1295 and ipamorelin improve „metabolism”, „energy levels” or „body composition” are based primarily on the general, well-established biological role of growth hormone and IGF-1 in regulating fat and protein metabolism. They are not based on direct clinical trials of these two peptides measuring metabolic rate or energy levels in humans. As discussed in earlier articles in this series, the strongest evidence in humans for CJC-1295 concerns its ability to raise growth hormone and IGF-1 levels in a dose-dependent manner [3]. The only clinical trial specifically designed to test a related metabolic outcome – the reduction of visceral fat in patients with HIV-associated lipodystrophy – was not completed. This leaves a real gap in the direct evidence regarding metabolic outcomes or, more specifically, those related to body composition [4].
Claims regarding subjective energy levels are not addressed by any research identified in the peer-reviewed literature reviewed for this series and should be understood as anecdotal rather than clinically demonstrated. With that said, statements describing CJC-1295 and Ipamorelin as having confirmed „metabolic benefits” go significantly beyond what direct clinical evidence currently supports – even if the underlying hormonal mechanism, raising growth hormone and IGF-1, is real and well-documented.
Limitations of current evidence
The concern regarding insulin sensitivity discussed in this article is rooted in sound, well-established general endocrinology concerning the relationship between growth hormone and the action of insulin. However, it has not been directly tested for CJC-1295 or ipamorelin through a dedicated study of glucose or insulin sensitivity.
The discovery of cortisol-sparing effects for ipamorelin is well-documented from its original pharmacological studies. However, this specific finding has not been directly replicated for CJC-1295 or for both compounds collectively.
Broader metabolic and energy-related claims are based on general physiological reasoning, rather than direct outcome data.
Disclaimer
This content is for educational and informational purposes only and should not be interpreted as medical advice, diagnosis, or therapeutic recommendation. CJC-1295 and ipamorelin remain research compounds and are not approved by the FDA or the European Medicines Agency for any medical use, whether used individually or in combination. No dedicated human studies have measured insulin sensitivity, blood glucose, or metabolic outcomes specifically for these two peptides. Anyone with diabetes, prediabetes, or other blood sugar concerns should be aware that the effects of these compounds on glucose regulation remain uninvestigated and unknown.
References
[1] Dominikowski, A., Rękoś, Z., Olejarz, M., Szczepanek-Parulska, E., Domin, R., & Ruchała, M. (2026). The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: Bridging the gap between clinical evidence and patient self-administration. Frontiers in Endocrinology, 17, Article 1822475. https://doi.org/10.3389/fendo.2026.1822475
[2] Raun, K., Hansen, B. S., Johansen, N. L., Thøgersen, H., Madsen, K., Ankersen, M., & Andersen, P. H. (1998). Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology, 139(5), 552–561. https://doi.org/10.1530/eje.0.1390552
Teichman, S. L., Neale, A., Lawrence, B., Gagnon, C., Castaigne, J. P., & Frohman, L. A. (2006). Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analogue of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology & Metabolism, 91(3), 799–805. https://doi.org/10.1210/jc.2005-1536
[4] National Centre for Biotechnology Information. (2026). PubChem Compound Summary for CID 91971820, CJC-1295 [Clinical trial data: NCT00267527 and EudraCT 2005-003797-25]. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/91971820