Written on January 21, 2024 by Amy Harris, MS, RN, CNM. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
Table of contents
If you are considering trying one of the GLP-1 agonists or your healthcare provider wants to prescribe you one for your diabetes control, it's important to be aware of possible side effects. While not a common side effect, with large amounts of weight loss and significant dietary changes, some people do experience hair thinning, hair loss, or alopecia. Keep reading to learn more about a possible connection between weight loss and hair loss.
Alopecia is the medical term for hair loss. Alopecia can impact the hair growing all over your body or just the hair growing on your scalp. Alopecia can be short-lived (temporary) or permanent.
It is normal for all human beings to shed hair throughout their lives and to have hair at three different stages of shedding at any point in time. The three stages of hair shedding are :
A condition called acute telogen effluvium (TE) is the medical term for the type of temporary hair loss caused by a stressor or change in your body. Telogen effluvium causes hairs to enter the resting stage (telogen) from the growing stage (anagen) prematurely and is the most common cause of diffuse hair loss. Most healthy people lose up to 100 strands of hair per day. If you have telogen effluvium, you may lose up to 300 strands of hair per day.
Your normal hair cycle results in the replacement of every hair on the scalp within three to five years. Telogen effluvium is generally diffuse (occurring all over your body) and happens three to four months after an acute stressor or change. After a stressor or change to your body, up to 70% of your hair in the anagen stage prematurely enters the telogen phase, which causes hair loss.
A particularly quick or large amount of weight loss counts as a stressor for your body. A significant change in your diet, the food you eat, weight loss surgery, or a new medication such as a GLP-1 agonist and the related weight loss could all cause hair loss and TE.
More severe cases of telogen effluvium may affect other areas of your body, such as your eyebrows and body hair. Acute telogen effluvium lasts shorter than 6 months, and in 95% of cases, it goes away (your hair will grow back).
TE is more likely to affect those AFAB and women.
Nutritional deficiency can impact both hair structure and growth. Vitamins and minerals are important for normal cell growth and function and may contribute to hair loss when they are deficient. Micronutrients like iron and B vitamins are integral to the hair follicle cycle, playing a role in cellular turnover, hair follicle development, and immune cell function.
The most commonly reported nutrient deficiencies linked with TE are deficiencies or diets low in [2,5]:
Some studies report that there is insufficient data to recommend zinc, riboflavin, folic acid, or vitamin B12 supplementation in cases of deficiency and TE. However, statistically significant differences were observed in pre- and post-operatory levels of zinc, Vitamin B12, and folic acid in one study of 50 laparoscopic sleeve gastrectomy patients. Neither vitamin E nor biotin supplementation is supported by the literature for treating TE. 
If you are interested in learning more about the medications available to help you lose weight, like the GLP-1 agonists, EverlyWell offers online weight management services. When people start a new diet or medication that changes the types of food they regularly eat, such as a GLP-1 agonist, they may notice changes in their hair or a few extra strands on their hair brush. The TE typically happens about three months after starting a new diet or medication and may last up to six months. Starting a poorly planned, so-called “crash diet” without sufficient micronutrients may increase the risk that you experience some hair loss as part of your weight loss plan.
Scientists believe that it is not these medications themselves (semaglutide and tirzepatide) causing hair loss, but instead the change in diet, food consumed, and amount of weight lost by people taking these drugs. Correct nutrition is required for the formation of healthy hair shafts and the promotion of hair growth. Without correct nutrition early in hair growth, you could be putting yourself at risk for hair loss and thinning in the form of TE later down the road.
Wegovy®’s clinical trials suggested that 3% of people who took the drug said they experienced hair loss, slightly higher than the 1% of the participants in the placebo who reported the same. More people taking the Type 2 diabetes medication Mounjaro® in a 2022 clinical trial noted alopecia—5.1% of people taking the 5 mg dose, 4.9% of people who took a 10 mg dose, and 5.7% of people who took a 15 mg dose. Only 1% of participants receiving the placebo did.
Weight loss surgery can lead to both weight loss and micronutrient deficiencies, resulting in hair loss. Two separate studies of weight loss surgery reported hair loss among the women undergoing the sleeve gastrectomy procedure. Of 50 women in a 2018 study, researchers reported observed hair loss in more than half. Another 2021 study reported that three-quarters of the 112 women having the sleeve gastrectomy procedure experienced hair loss in the three to four months following surgery.
While terrifying to look down at your hairbrush and see it full of precious strands of hair, it can be reassuring to know that 95% of telogen effluvium goes away on its own.
If you have lost a significant amount of weight, have started one of the new GLP-1 agonist medications, or suspect you might have some micronutrient deficiencies, talking to your healthcare provider may be able to provide you with some reassurance. They can help you follow a more balanced plan for consuming ALL of the necessary nutrients for a healthy head and scalp as well as a healthy weight.
Everlywell's comprehensive Weight Care+ program offers access to discreet virtual care and visits with a licensed healthcare provider to help you manage your weight loss journey. A variety of benefits are on offer, including periodic at-home lab testing in most states, lifestyle guidance and support, and even supplements and prescriptions, depending on your situation, location, and the recommendations of a licensed healthcare provider.
Amy Harris, MS, RN, CNM has a master's degree in Maternal and Child Health from Harvard T. Chan School of Public Health. She attended Yale School of Nursing and Boston University School of Public Health to become a certified nurse midwife (CNM). She has worked for over 20 years in clinical and public health practice and has published in scientific publications such as the Journal of Midwifery and Women's Health. She specializes in women's reproductive health care, healthy literacy, and writing about health and wellness.