How Common Mounjaro Hair Loss Is

In the trials behind Mounjaro’s UK licence, 4.9% of people on tirzepatide reported hair loss against 1.0% on placebo, and most recovered while still taking it (Mounjaro SmPC, section 4.8). Marked weight loss is a known trigger, with shedding that starts about 3 months later and lasts 3 to 6 months (BAD patient leaflet).

Key facts

• No one on tirzepatide in those trials stopped treatment because of hair loss (Mounjaro SmPC, section 4.8).
• Hair loss was reported by 7.1% of women on tirzepatide in the US Zepbound trials, against 0.5% of men (Zepbound prescribing information, section 6.1).
• A 2026 BMJ records study linked starting a GLP‑1 with a higher risk of non-scarring hair loss, while calling the absolute risk low (Tang et al., 2026).
• Losing 30 to 150 hairs a day is normal, and starting a new medicine is itself on the dermatologists' list of triggers (BAD patient leaflet).

How common hair loss is on Mounjaro, Zepbound and Wegovy

The Mounjaro and Wegovy rows come from their Summaries of Product Characteristics (SmPCs), the UK prescribing documents (Mounjaro, Wegovy 2.4 mg and Wegovy 7.2 mg SmPCs, section 4.8). The Zepbound rows come from its US label (Zepbound prescribing information, section 6.1).

Zepbound is the US brand name for tirzepatide. In the UK the same medicine is Mounjaro, licensed for both type 2 diabetes and weight management under one SmPC (Mounjaro SmPC, section 4.1).

Split by sex, the Zepbound figures are 7.1% of women and 0.5% of men on tirzepatide, against 1.3% and 0% on placebo (Zepbound prescribing information, section 6.1). Other effects that matter for women, including the pill warning, are in Mounjaro side effects in women.

A 2026 study in The BMJ followed adults with type 2 diabetes who started a GLP‑1 medicine, an SGLT-2 inhibitor or a DPP-4 inhibitor from 2019 to 2024 (Tang et al., 2026). In their Penn Medicine health records, hair loss was more likely after starting a GLP‑1 medicine, with hazard ratios of 1.37 against SGLT-2 inhibitors and 1.68 against DPP-4 inhibitors (Tang et al., 2026). The link was specific to non-scarring hair loss and weakened after a calibration against negative control outcomes, and the authors describe the absolute risk as low.

Why hair sheds during fast weight loss

At any time about 15% of scalp hair is resting and the rest is growing, and in telogen effluvium the resting share rises to 30% or more (BAD patient leaflet). The extra hairs are shed about 3 months after the trigger, or 1 to 6 months in the range StatPearls gives (BAD patient leaflet; StatPearls, Telogen Effluvium).

Marked weight loss and extreme dieting are on the British Association of Dermatologists' list of common triggers, and for 1 in 3 people with telogen effluvium no cause is found (BAD patient leaflet). StatPearls adds crash dieting, low protein intake and iron deficiency (StatPearls, Telogen Effluvium).

The shedding comes well after the nausea, vomiting and diarrhoea, which on Mounjaro are more common during the weeks of dose escalation and decrease over time (Mounjaro SmPC, section 4.8). Fast weight loss takes lean tissue too, and in the SURMOUNT-1 body scans about a quarter of the weight lost on tirzepatide was lean mass (Look et al., 2025).

The shedding shows as thinner hair and less volume across the scalp rather than as patches (BAD patient leaflet). Telogen effluvium does not scar the follicles, which is why the hair is expected to come back (StatPearls, Telogen Effluvium).

Will hair grow back after Mounjaro?

In the usual course, yes. The British Association of Dermatologists says "Telogen effluvium usually gets completely better without any treatment", after a shedding phase of 3 to 6 months (BAD patient leaflet). Shedding that lasts more than 6 months counts as chronic (BAD patient leaflet). Regrowth can take up to 6 months to restart and several months to a year to restore full thickness (StatPearls, Telogen Effluvium).

Those timelines count from a single event, such as an illness, while weight loss on Mounjaro goes on for months. We found no study that has timed regrowth on tirzepatide. The labels tie the shedding to weight reduction (Zepbound prescribing information, section 6.1; Wegovy 2.4 mg SmPC, section 4.8), which suggests the settling period starts once your weight levels off.

Telogen effluvium can also lead to an earlier diagnosis of pattern hair loss, which looks similar and sometimes appears at the same time (BAD patient leaflet). If thickness does not return once the shedding stops, that needs its own assessment.

What helps

Low protein intake is one recognised trigger, so check that you are eating enough (StatPearls, Telogen Effluvium). The GLP‑1 protein calculator turns your weight into a daily target, from the published protein ranges for people on a GLP‑1.

Correcting low iron, zinc or vitamin D lets hair growth return (StatPearls, Telogen Effluvium), and the British Association of Dermatologists suggests a balanced diet with foods rich in iron and protein (BAD patient leaflet). Your GP can check with a blood test. When iron deficiency is suspected, StatPearls recommends a full blood count, serum iron, iron saturation and ferritin, and a thyroid test when there are symptoms of an underactive thyroid (StatPearls, Telogen Effluvium).

For the hair you have, avoid harsh brushing, limit heated styling tools and tight hairstyles, and skip bleaching or relaxing treatments (BAD patient leaflet).

Because shedding starts about 3 months after its trigger, counting back from the week it began points to what set it off (BAD patient leaflet). The weight report in Pensday shows how fast you were losing on each dose at that point.

When to see your GP

See your GP if any of these apply (BAD patient leaflet; StatPearls, Telogen Effluvium):

• the hair loss is in patches rather than thinning all over the scalp
• shedding has gone on for more than 6 months, or is not getting better
• you have signs of an underactive thyroid, such as tiredness, constipation or feeling the cold
• you think you may be low in iron

Patchy loss suggests something other than telogen effluvium. StatPearls lists alopecia areata and pattern hair loss among the conditions that can look similar (StatPearls, Telogen Effluvium).