Growth hormone is well established in general endocrinology as having an insulin-antagonistic effect on the body. This means that CJC-1295 and ipamorelin, both of which increase growth hormone levels, could potentially influence 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 rooted in solid general physiology, rather than a directly confirmed 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 works in part by counteracting some of insulin's effects on cells. This is a normal part of how the body balances energy utilization and storage. However, it also means that sustained periods of elevated growth hormone can reduce the effectiveness with which insulin lowers blood sugar. This is a phenomenon well recognized in conditions of chronic growth hormone excess, such as acromegaly, and in some patients receiving growth hormone replacement therapy.
Because both CJC-1295 and ipamorelin are specifically designed to elevate growth hormone secretion, it is a reasonable, mechanistically sound expectation that they might have some effect on insulin sensitivity or blood glucose regulation. This concern is reflected in a 2026 review of performance-enhancing peptides acting on the growth hormone–IGF-1 axis. This review listed dysglycemia—abnormal regulation of blood sugar—among the endocrine and metabolic derangements 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 a category level rather than presenting data from a controlled study that directly measured 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.
Regarding specific use in people with diabetes, no published studies address the safety or effects of these peptides in the diabetic population. Given the likely mechanism described above, this constitutes a significant unknown, not 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.
Effects of CJC-1295 and Ipamorelin on Cortisol
Cortisol is a stress-related hormone that some older growth hormone-releasing peptides are known to increase as an undesirable side effect. One of ipamorelin's most notable and well-documented features, dating back to its original pharmacological characterization, 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 like GHRP-6 and GHRP-2. They found that while these older compounds increased plasma ACTH—the pituitary hormone that triggers cortisol release—and cortisol itself, ipamorelin did not induce a significant rise in either. This remained true even at doses over 200 times the amount needed to trigger growth hormone release [2].
This selectivity is considered one of the defining pharmacological characteristics of ipamorelin. This is 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 detailed cortisol analysis as part of its published results. Therefore, direct human data regarding the effect of CJC-1295 on cortisol specifically is not available within the literature reviewed here. However, it is worth noting that as a GHRH analog acting through a different receptor system than the ACTH-releasing pathway, there is no obvious mechanistic reason to expect it to raise cortisol in the way older GHRP-type compounds did.
However, it is worth being precise that the well-documented discovery of low cortisol described above comes specifically from ipamorelin's own baseline research [2] - and not from the CJC-1295 study or both compounds together.
Metabolic benefits of CJC-1295 and ipamorelin
Beyond the previously discussed questions about insulin and cortisol, broader claims about CJC-1295 and ipamorelin improving „metabolism,” „energy levels,” or „body composition” are largely based 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 outcome studies 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 relates to 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—visceral fat reduction in HIV-associated lipodystrophy patients—was not completed. This leaves a real gap in direct evidence for metabolic or body composition-related outcomes specifically [4].
Claims about subjective energy levels are not addressed by any studies 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 substantiated „metabolic benefits” go far beyond what direct clinical evidence currently supports—even if the underlying hormonal mechanism, the raising of 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 solid, well-established general endocrinology concerning the growth hormone's relationship with insulin action. However, it has not been directly tested for CJC-1295 or ipamorelin through a dedicated glucose or insulin sensitivity study.
Cortisol-sparing effects for ipamorelin are well-documented from its original pharmacological studies. However, this specific finding has not been directly replicated for CJC-1295 or for both compounds in combination.
Broader metabolic and energy-related claims are based on general physiological reasoning, not direct outcome data.
Disclaimer
This content is for educational and informational purposes only and should not be construed as medical advice, diagnosis, or treatment recommendation. CJC-1295 and ipamorelin remain research compounds and are not approved by the FDA or European Medicines Agency for any medical use, whether used individually or in combination. No dedicated human trials 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 unstudied and unknown.
References
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
[3] 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 analog 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 Center 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