GLP-1s & Unexpected Side Effects: This One’s Growing
It's hard to miss how often hair loss comes up in patient forums discussing GLP-1s. This observation prompted me to take a closer look at this common concern associated with medications like semaglutide and tirzepatide. As these drugs become go-to options for weight management, more patients will understandably ask about potential side effects like hair thinning. Let's take a quick look at what the current research and expert opinions suggest, in the hope we can better support our patients navigating this tricky subject.
What Current Research Says
Hair loss, or alopecia, has been reported in clinical trials for GLP-1 medications approved for obesity, though typically not as a common side effect (<5%).
Semaglutide (Wegovy): Trials showed hair loss in 3% of adults (vs. 1% placebo) and 4% of adolescents (vs. 0% placebo).
Tirzepatide (Zepbound): Trials reported hair loss in 4-5% of participants (vs. 1% placebo). Notably, this was more frequent in females (7.1%) compared to males (0.5%), though no participants discontinued the trials due to hair loss.
Tirzepatide (Mounjaro): While not listed as an adverse effect in the official package insert, one 2022 study observed alopecia in 4.9% to 5.7% of users (vs. 0.9% placebo).
Emerging Research & FDA Oversight
Recent pre-print research suggests GLP-1 users might have a higher risk of hair loss compared to those on older weight loss medications like Contrave, particularly women. This potential difference is hypothesised to relate to the greater amount and speed of weight loss often achieved with GLP-1s.
Given the increased attention on GLP-1 side effects generally, the FDA is actively investigating various reports, including hair loss, as part of its ongoing safety monitoring (pharmacovigilance).
Understanding the Causes
The prevailing expert opinion is that hair loss experienced during GLP-1 therapy is not typically a direct pharmacological effect of the drug itself. Instead, it's largely attributed to:
Rapid Weight Loss: This is a well established trigger for a condition called Telogen Effluvium (TE), the most common form of hair loss reported in this context. TE is a temporary condition where hair sheds diffusely across the scalp. It's triggered when major body stress, such as rapid weight loss, causes a high number of hair follicles to prematurely enter their resting state (the telogen phase) instead of their active growing state (the anagen phase). These resting hairs eventually fall out, leading to increased shedding usually seen about three months after the stress started.
Nutritional Factors: Appetite suppression with GLP-1s can lead to reduced overall energy intake and potentially inadequate intake of key nutrients vital for hair health. Deficiencies in protein, iron, zinc, B vitamins (especially B12 and folate), and potentially Vitamin D can contribute to or exacerbate hair thinning.
Lessons from Bariatric Surgery
The experience following bariatric surgery provides a strong parallel. Hair loss is a known and anticipated side effect, generally beginning at 3 months post-surgery. It's linked directly to the rapid weight loss, associated hormonal shifts, and potential nutrient deficiencies. Crucially, in most bariatric cases, hair regrows as weight stabilises and nutritional status improves.
Takeaways for Health Professionals
Hair loss can be distressing for people and potentially impact their adherence and overall wellbeing during their weight management journey.
Here’s a few key areas where we can provide support:
Inform: Educate patients about potential temporary hair loss associated with GLP-1 medications.
Reassure: Help patients understand that this hair loss is usually transient and should improve as weight and nutritional status stabilises
Nutrition guidance: Stress the importance of adequate protein intake and essential micronutrients (especially iron, zinc, B12, folate and vitamin D) during weight loss.
Advise on Supplementation: Recommend a standard multivitamin or appropriate supplement if dietary intake is compromised (note that over supplementation of Vitamin A has been reported to increase hair loss).
Refer: If hair loss is causing psychological distress, refer back to prescriber.
References
Diet and hair loss: effects of nutrient deficiency and supplement use - PMC, accessed on 23 March 2025, pmc.ncbi.nlm.nih.gov/articles/PMC5315033
Mounjaro (tirzepatide) prescribing information. Eli Lilly. Indianapolis, IN. Revised July 2023. Accessed March 2025 at uspl.lilly.com/mounjaro/mounjaro.html#pi
Wegovy (semaglutide) prescribing information. Novo Nordisk. Bagsvaerd, Denmark. Revised July 2023. Accessed March 2025 at novo-pi.com/wegovy.pdf
Zepbound (tirzepatide) prescribing information. Eli Lilly. Indianapolis, IN. Revised November 2023. Accessed March 2025 at accessdata.fda.gov/drugsatfda_docs/label/2023/217806s000lbl.pdf
Do Ozempic, Wegovy, Mounjaro & Zepbound cause hair loss?, accessed on 23 March 2025, drugs.com/medical-answers/ozempic-wegovy-mounjaro-cause-hair-loss-3575019medrxiv.org, accessed on 23 March 2025, medrxiv.org/content/10.1101/2025.02.23.25322568v2.full.pdf
Ozempic, Wegovy side effects: Suicidal ideation, hair loss – Medical News Today, accessed on 23 March 2025, medicalnewstoday.com/articles/ozempic-wegovy-side-effects-suicidal-ideation-hair-loss
Telogen Effluvium – British Association of Dermatologists, accessed on 23 March 2025, bad.org.uk/pils/telogen-effluvium/
Thanks for reading!
Leif
Got feedback? Email leif@glp1dietitianhub.com, I'd love to hear from you.
Note: This newsletter is for educational purposes only and should not be considered medical advice. Always consult a qualified healthcare professional for personalised guidance.
Subscribe for free to receive new posts and support my work