MODI HAIR MEDICAL GUIDE
If your hair is falling out after a weight-loss injection
If you notice a lot of hair shedding after using Wegovy or Mounjaro, you may wonder whether it is caused by the medication or by the weight loss itself. Rapid weight change can be a trigger for telogen effluvium, but an individual's cause cannot be attributed solely to the medication or to weight loss. Your medication history, rate of weight loss, dietary status, pre-existing hair loss and comorbid conditions all need to be reviewed together.
Three-line summary
- Hair loss occurring during weight loss may involve multiple factors, including weight change, nutrition, hormones and the pre-existing condition of the hair.
- A preprint comparing the two agents observed a difference in recorded hair loss, but a direct causal relationship with the medication has not been established.
- If hair loss occurs, rather than changing your prescribed medication on your own, inform both the prescribing medical team and the scalp and hair medical team about how things are progressing.
Weight-loss injections and hair loss, explained on video
Based on a video by Director Yoo Hwa-jung of Modi Hair Plant Clinic and related materials, we look at what the research observed and what has not yet been confirmed. The text below adds interpretation of the statistics and the limitations of the research.
What ingredients are Wegovy and Mounjaro?
Both medications work through incretin signaling, but they act on different receptors. Even for the same ingredient, the intended use and prescribing information may differ depending on the brand name, formulation, dose and country of approval.
Semaglutide
An ingredient contained in products such as Wegovy and Ozempic, acting on the GLP-1 receptor.
Tirzepatide
An ingredient contained in Mounjaro and Zepbound, acting on the GIP and GLP-1 receptors.
In SURMOUNT-5, a head-to-head trial in adults with obesity without diabetes, the mean weight change after 72 weeks of treatment at the maximum tolerated dose was −20.2% in the tirzepatide group and −13.7% in the semaglutide group. These are average results under specific trial conditions and do not guarantee individual weight-loss outcomes.[2]
Is hair loss also listed in the product prescribing information?
The U.S. FDA prescribing information lists hair loss as an adverse reaction for Wegovy and Zepbound. In pooled data from adult weight-loss trials of Wegovy 2.4 mg, it was reported in 3.3%, versus 1% in the placebo group. In pooled data from the Zepbound weight-loss trials, it was reported in 4–5% depending on dose, versus 1% in the placebo group.[3], [4]
Both sets of prescribing information describe hair loss as an adverse reaction associated with weight loss. However, adverse reaction rates from different trials should not be compared directly to conclude that one medication is safer. The figures above come from data for those specific U.S. products and doses, and do not replace domestic product approval information.
What did the recent comparative study find?
Start by checking the nature of the study. It is a retrospective electronic medical record analysis released on 20 July 2026, and the version reviewed is a preprint that has not undergone peer review. It compared users who had no record of hair loss before the prescription.[1]
| Analysis | Semaglutide | Tirzepatide |
|---|---|---|
| Baseline characteristic matching · 12,863 people each | 2.88% | 4.20% |
| Additional matching by weight-loss percentage band · 11,046 people each | 3.33% | 4.24% |
In the additionally matched analysis, the relative risk was 1.27 and the absolute difference was 0.91 percentage points. The 95% confidence interval was 1.11–1.45. This was not a comparison of people who lost exactly the same amount of weight, and the figures should not be reinterpreted as brand-specific numbers.[1]
Does this mean the medication itself causes hair loss?
That cannot be concluded. The rate of weight loss, food intake and other factors were not fully controlled, and medical records are subject to omissions and reporting bias. Nor does it mean that everyone without a record lost weight without hair loss.[1]
Although some repeated nutritional tests showed no clear decrease, a nutritional cause cannot be ruled out. The finding in an exploratory RNA analysis that receptor signaling was not detected in hair follicle keratinocytes is also not evidence ruling out a direct action. The involvement of the surrounding immune and vascular environment is a hypothesis.[1]
When the hair falls out, and telogen effluvium
Telogen effluvium is a condition in which many hair follicles shift into the resting phase, increasing shedding across the scalp overall. Rapid weight loss, dietary restriction, illness and hormonal changes can all be triggers, and it may appear several months after the cause occurs.[5], [6]
In the comparative study, the cumulative record curves diverged from around 6 months. This should not be interpreted as "most cases start at 5–6 months" or "all cases are telogen effluvium." There were also more records of new minoxidil prescriptions, but that does not itself measure the need for treatment.[1]
What else should be checked?
In the group that developed hair loss, women and a history of certain endocrine disorders were relatively common. The figures of 28.1% and 21.6% for hypothyroidism in the original paper are the proportions with that medical history within the tirzepatide group according to whether hair loss was recorded, not the incidence of hair loss among patients with thyroid disease. They also cannot be used for definitive prediction of individual risk.[1]
At your consultation, it helps with assessing the cause if you share not only a history of thyroid disease or polycystic ovary syndrome, but also menstrual changes, recent illness, dietary restriction, use of other medications, and changes in your existing part line and hairline. Which tests are performed is decided based on your symptoms and examination findings.[5], [6]
If hair loss occurs while using a weight-loss injection
It is important to weigh the benefits and the drawbacks of the treatment together. Rather than stopping, reducing or changing your prescribed medication on your own, inform the prescribing medical team about your hair loss symptoms and the course of your weight change. Through a dermatology consultation, the cause can be reviewed and the necessary management approach determined.[7]
What to prepare before your consultation
- The date you started the medication and any dose change history
- Weight changes and when the shedding began
- Food intake, protein intake, and symptoms such as vomiting that interfered with eating
- Underlying conditions and use of other medications or supplements
What is checked at a scalp consultation
- Whether shedding is diffuse or specific areas are thinning
- Whether pre-existing androgenetic alopecia is also present
- Whether there is scalp inflammation or another hair loss condition
- Whether blood tests and treatment are needed
Supplements and minoxidil are not equally necessary for everyone. It is better to decide whether to use them after checking whether there is a nutritional deficiency and what type of hair loss is involved. If a round bald patch appears suddenly, or if there is accompanying pain or redness, do not dismiss it as simple weight-loss-related hair loss — seek a consultation.
Frequently asked questions about Wegovy, Mounjaro and hair loss
Does using Wegovy or Mounjaro always cause hair loss?
It does not always occur. Hair loss is one of the reported adverse reactions, but not all users experience it. Individual symptoms need to be assessed together with weight change, diet, health status and pre-existing hair loss, not just medication use.
If my hair starts falling out, should I stop the medication right away?
Do not stop it or switch to another medication on your own; consult the prescribing medical team. The decision on whether to continue or adjust should be made after reviewing the purpose of treatment, weight change, the degree of symptoms and other possible causes.
Can I choose between Wegovy and Mounjaro based only on concerns about hair loss?
The choice of medication is difficult to decide based on hair loss data alone. It should be decided together with the prescribing medical team, considering the approved indications, comorbid conditions, the expected treatment effect and the overall adverse reaction profile.
Does hair loss that occurs after weight loss recover?
Telogen effluvium often recovers once the trigger is resolved, but the speed and extent of recovery vary. Another type of hair loss may also be present, so if it persists or worsens it is advisable to have the cause checked.
Can it be prevented by using minoxidil or supplements in advance?
It is difficult to regard this as a method with established preventive effect for all users. Check whether there is a deficiency and what type of hair loss is involved, and discuss the need for treatment with a medical professional. The fact that there were more prescriptions in the study alone is not a basis for recommending preventive use.
Review your weight changes and hair condition together
At Modi Hair Plant Clinic, you can receive a consultation on your scalp and hair condition. Please discuss any change to obesity or diabetes medication with the medical team that prescribed it.
This article is intended to provide general medical information and does not replace individual diagnosis or prescription. The cause of hair loss and whether treatment is appropriate are determined after a consultation, and results vary between individuals. The comparative study is described based on the pre-peer-review version reviewed on 7 September 2026. Approval information for each product may differ depending on country, indication, formulation and dose.
References and source materials
- Marwaha A, Venkatakrishnan AJ, Murugadoss K, Soundararajan V. New-Onset Alopecia Is Significantly Higher with Tirzepatide than with Semaglutide, Even After Weight-Loss Matching. Preprints.org. 2026 Jul 20. Version 1. Manuscript 202607.1370. Preprint, not peer reviewed. View the original text and tables
- Aronne LJ, et al.; SURMOUNT-5 Trial Investigators. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. N Engl J Med. 2025;393:26-36. DOI: 10.1056/NEJMoa2416394. Paper
- U.S. Food and Drug Administration. WEGOVY prescribing information. 2026. Reference ID 5819850. Section 6.1, Hair Loss. U.S. FDA prescribing information
- U.S. Food and Drug Administration. ZEPBOUND prescribing information. 2026. Reference ID 5731061. Section 6.1, Table 1 and Hair Loss. U.S. FDA prescribing information
- Hughes EC, Syed HA, Saleh D. Telogen Effluvium. StatPearls. StatPearls Publishing. PMID: 28613598. PubMed
- Shrivastava SB. Diffuse hair loss in an adult female: approach to diagnosis and management. Indian J Dermatol Venereol Leprol. 2009;75(1):20-27. DOI: 10.4103/0378-6323.45215. PMID: 19172026. PubMed
- American Academy of Dermatology. How can GLP-1 drugs affect my skin, hair, and nails? American Academy of Dermatology patient guide