Do GLP-1 Drugs Raise Testosterone? What the Evidence Says So Far

Do GLP-1 Drugs Raise Testosterone? What the Evidence Says So Far

In men with obesity, weight-loss drugs may lift low testosterone — but the data are small, short, and mostly indirect.

Key takeaways

  • In men with obesity or type 2 diabetes and low testosterone, GLP-1 receptor agonists (semaglutide, liraglutide, tirzepatide) were associated with modest testosterone increases in small, mostly non-randomised studies.
  • The rise appears to track weight loss and better metabolic health rather than a proven direct effect on the testes. In healthy men with normal testosterone, results show no change.
  • Certainty of evidence is low. These drugs are not a replacement for testosterone therapy in men with classical (organic) hypogonadism.

01 — Why obesity lowers testosterone

Body fat and testosterone have a two-way relationship. Excess adipose tissue and insulin resistance lower SHBG (the carrier protein) and blunt signalling from the brain to the testes, which lowers total testosterone. Low testosterone, in turn, tends to favour fat gain. Clinicians call the result "functional hypogonadism": low levels driven by metabolic state rather than testicular disease. Weight loss is known to raise testosterone in this setting, which is why GLP-1 drugs, now widely used for obesity, attract attention.

02 — What the newest review found

A systematic review published in Cells in July 2026 (Zafrani, Khan and Zitzmann; PROSPERO-registered, PRISMA-guided) searched studies from January 2021 to January 2026 on GLP-1 receptor agonists and male reproductive hormones. It found that total testosterone rose in most studies of men with obesity, type 2 diabetes or functional hypogonadism, while a trial in healthy, eugonadal men showed no change versus placebo. LH and FSH rose or were preserved, which suggests the reproductive axis is not suppressed. The authors graded certainty as low for testosterone and very low for semen parameters, and concluded the effect is most likely metabolic rather than a direct androgen stimulus.

A conference report from ENDO 2026 (June 2026) points the same way: in short trials, liraglutide (16 weeks) was linked to roughly a one-third rise in total testosterone and semaglutide (24 weeks) to roughly a quarter or more, while dulaglutide over four weeks in healthy men changed nothing. That report is a press interview about a conference presentation; I could not confirm peer review.

03 — What this does NOT show

It does not show that GLP-1 drugs treat hypogonadism, improve symptoms such as libido or energy in a reliable way, or are safe for fertility planning. Fewer than a dozen small studies, different drugs, different durations, and inconsistent reporting of free testosterone limit every conclusion.

Key figures

For clinicians

  • Design: Systematic review, PRISMA 2020, PROSPERO CRD420261370402; RoB 2 for randomised and ROBINS-I for non-randomised studies; no meta-analysis because of heterogeneity.
  • Sample: Seven to eight studies depending on which section is read; individual sample sizes in the summary table appear to total about 466 men, whereas the text cites roughly 1,200 — an internal inconsistency worth noting.
  • Effects: Increases in total testosterone in most obesity/T2DM cohorts; one study (Graybill et al.) found no overall change but a rise in men with baseline T below 320 ng/dL or meaningful HbA1c reduction. SHBG rose in two studies by La Vignera et al.; free testosterone was inconsistently reported.
  • Limitations: Mostly non-randomised, moderate-to-serious bias, short follow-up, unknown durability, effect of weight loss cannot be separated from drug effect.
  • Practice points: Diagnosis of hypogonadism still needs symptoms plus repeated early-morning fasting low testosterone (Endocrine Society 2018). Consider re-checking testosterone after substantial weight loss before starting or continuing therapy, rather than assuming either direction.

What's new in regulation

On 6 January 2026 the US FDA updated its General Wellness guidance (replacing the 2019 version). Per law-firm summaries, non-invasive wearables that estimate physiologic parameters can, under certain conditions, be marketed as wellness products if they make no claims to screen, diagnose, monitor or manage a disease, and do not label outputs as abnormal or pathological. The guidance is non-binding. I did not find a verified, hormone-specific FDA clearance or CE/IVDR update this cycle, so none is claimed here.

What this means for patients

If you are on a GLP-1 drug and worry about low testosterone, do not self-start testosterone or supplements. Ask your doctor for a morning blood test, repeated if low, ideally alongside SHBG, LH and FSH. Low sex drive or fatigue on these drugs has many causes, including rapid weight loss, sleep, mood and low calorie intake. Planning a pregnancy? Discuss it with your doctor before relying on any of these findings.

Disclaimer: Educational content, not medical advice. Consult a physician about your own health.

6Letters is developing non-invasive wearable hormone monitoring (MOJO KING); it is a research and wellness effort, not a diagnostic tool. Learn more at https://6letters.co.kr.

References

  1. Zafrani Z, Khan SS, Zitzmann M. Metabolic Reversal of Functional Hypogonadism? GLP-1 Receptor Agonists and Male Reproductive Endocrinology — A Systematic Review. Cells. 2026;15(15):1319. doi:10.3390/cells15151319. https://pmc.ncbi.nlm.nih.gov/articles/PMC13464801/
  2. Natesh P, et al. GLP-1 receptor agonists and testosterone parameters in obese men with hypogonadism (ENDO 2026 presentation; interview published 2 July 2026). https://medicalresearch.com/endo-2026-glp-1-receptor-agonists-may-improve-testosterone-parameters-in-obese-men-with-hypogonadism-without-suppressing-male-reproductive-axis/
  3. Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018. PMID 29562364. https://pubmed.ncbi.nlm.nih.gov/29562364/
  4. Foley & Lardner LLP. Digital Health Policy: FDA relaxes restrictions over wearables and AI decision-making tools in two new 2026 guidances (January 2026). https://www.foley.com/insights/publications/2026/01/digital-health-policy-fda-relaxes-restrictions-over-wearables-and-ai-decision-ma/