Hair Shedding on GLP-1 Medications: What Could Be Causing It?

How often is hair loss reported on the labels?

The Wegovy injection label reports hair loss in 3% of patients on semaglutide 2.4 mg versus 1% on placebo, from a pool of three weight-management trials that included 2,116 semaglutide-treated and 1,261 placebo-treated adults [1]. The Zepbound label reports hair loss in 4% to 5% of tirzepatide-treated patients versus 1% on placebo [2]. The Foundayo label reports hair loss in 4% of patients on 5.5 mg and on 9 mg and 5% on 17.2 mg, versus 2% on placebo, in a pool of 3,155 treated adults [3].

The sex difference is visible in the Foundayo data: at 17.2 mg the reaction was reported by 7% of women and 0.9% of men, and hair loss is described as more common in women [3][1][2].

These percentages come from different trials and populations, so they cannot show that one drug causes hair loss more often than another [1][3].

What do the labels say is causing it?

The labels' explanation is weight reduction [1][3][2]. For scale, weight change was -14.9% with semaglutide 2.4 mg versus -2.4% with placebo over 68 weeks in STEP 1, and -20.9% with tirzepatide 15 mg versus -3.1% with placebo over 72 weeks in SURMOUNT-1 [6][7]. In the Foundayo weight-management trial, the 17.2 mg dose produced an 11.1% weight reduction versus 2.1% on placebo over 72 weeks [3].

Telogen effluvium: a pattern that can fit rapid weight loss

Hair grows in three phases: anagen (active growth, about 90% of hairs), catagen (less than 10%) and telogen (resting, 5% to 10%), and hair is shed during telogen [4]. Telogen effluvium is a non-scarring, non-inflammatory hair loss of relatively sudden onset caused by physiologic or emotional stress; once the precipitating cause is removed, the hair typically regrows [4]. Diffuse hair loss is commonly due to telogen or anagen effluvium rather than to a patchy process [4]. A 2017 review in American Family Physician notes that history and physical examination are often enough to identify the specific cause of hair loss [4].

What else can cause diffuse shedding?

Androgenetic alopecia. Common pattern hair loss can be diffuse or follow a specific pattern and may progress to complete baldness; the review says it can be diagnosed clinically and treated with minoxidil, and it is a different diagnosis from telogen effluvium [4].

Anagen effluvium. This is diffuse loss of hair during the growth phase, caused by an event that impairs the mitotic activity of the hair follicle, most commonly chemotherapy [4].

Patchy loss points elsewhere

Alopecia areata produces typical patches of hair loss and is self-limited [4]. Tinea capitis causes patches of alopecia that may be red and scaly and must be treated systemically [4]. Trichotillomania is an impulse-control disorder in which hair is pulled out, and treatment targets the underlying psychiatric condition [4].

Does the specific drug change the answer?

The labels give hair-loss rates and tie them to weight reduction for each drug [1][3][2]. Tirzepatide's label describes it as a dual GIP and GLP-1 receptor agonist rather than a pure GLP-1 agonist, and Foundayo contains orforglipron, a small-molecule oral GLP-1 receptor agonist rather than semaglutide [2][3].

Do FDA adverse event reports prove the drug caused the shedding?

No. FDA's adverse event dashboard states that a report does not establish that a drug caused the event, that reports are often duplicated or incomplete, and that the data cannot be used to estimate how often an event occurs [5]. Reports of hair loss filed for semaglutide, tirzepatide or orforglipron therefore cannot show that the drug, rather than weight loss or something else, produced the shedding.

Does the hair grow back?

For telogen effluvium, the hair typically regrows once the precipitating cause is removed [4]. Androgenetic alopecia behaves differently and can progress [4].