Why Mounjaro Can Cause Dry, Brittle Hair — and What Helps

What the SURMOUNT-1 trial data tell us about hair during tirzepatide treatment

When researchers reviewed adverse events across the SURMOUNT-1 trial (which randomised 2,539 adults with obesity over 72 weeks) alopecia (hair loss and altered hair texture) was recorded more often in the tirzepatide groups than in the placebo group, with rates broadly consistent with what has been reported for other GLP-1 medicines at therapeutic weight-loss doses. Hair changes, including dryness and brittleness, appeared most frequently during the dose-escalation phase and in the period of steepest weight reduction. The NHS tirzepatide medicines page lists hair loss among the less common side effects worth discussing with your prescriber if it becomes a concern. What the trial data cannot easily separate is how much of any hair change is a direct pharmacological effect versus a consequence of rapid caloric deficit and shifting nutritional balance. Most clinicians attribute the bulk of it to the latter.

Rapid weight loss, by almost any method, reduces the supply of energy and micronutrients reaching hair follicles. Follicles are metabolically expensive tissue; they are shed first when the body economises. Tirzepatide suppresses appetite significantly (that is precisely its mechanism) so unless protein and micronutrient intake are actively maintained, hair quality can suffer. A question our prescribers hear most weeks is whether the dryness means something is wrong with the medicine; in the majority of cases, it is a signal about diet rather than about the drug itself.

Why dryness specifically, rather than just shedding

Telogen effluvium is the term for the follicle-phase shift that underlies most treatment-related hair loss, and shedding is its most visible sign. Dryness and a change in hair texture, however, have an additional nutritional explanation. Hair shaft quality depends on adequate intake of protein (keratin is its structural unit), fatty acids, iron, zinc, biotin and other B vitamins. When caloric intake falls sharply, as it often does in the early months on tirzepatide, the diet can become inadvertently low in one or more of these. Sebum production (the scalp's natural conditioning mechanism) also responds to caloric and fat intake; a low-fat diet taken too far can reduce sebum, leaving hair feeling dry and prone to breakage.

Hydration is a less-discussed factor. Tirzepatide slows gastric emptying, and some people drink less throughout the day without noticing. Mild, persistent under-hydration affects the scalp and hair shaft. Drinking enough water consistently (not just at meals) is a simple, often overlooked step. You can find broader guidance on lifestyle habits alongside treatment on our weight-loss treatment overview.

What you can actually do about it

The practical advice from clinicians and dietitians in this area clusters around three priorities. First, protect protein intake. On a reduced-calorie diet, aiming for at least 1.2–1.6 g of protein per kilogram of body weight per day is a widely cited target for preserving lean mass and supporting hair; personal targets should be confirmed with your prescriber or a dietitian. Second, review micronutrient status. Iron-deficiency is particularly associated with hair texture changes in women; a blood test can confirm whether supplementation is warranted. A broad B-complex supplement, if dietary variety has narrowed, is low-risk and commonly recommended. Third, avoid compounding the problem with harsh hair care. Heat styling and chemical treatments on already-stressed hair shafts increase breakage and perceived dryness.

It is also worth knowing that the timeline matters. Hair texture typically stabilises as weight loss slows and the body reaches a new equilibrium. Most people who report hair dryness in months two to four find it improves by months six to nine without changing their treatment. If dryness is accompanied by significant shedding, the fuller picture is covered in our guide to losing hair on Mounjaro and in the deeper look at how tirzepatide affects the hair more broadly.

When to raise it with your prescriber

Dry hair alone, in the absence of other symptoms, is not a medical emergency. It is, however, worth mentioning at your next clinical review — particularly if it is accompanied by significant shedding, scalp changes, fatigue, or if it began shortly after a dose increase. A prescriber can check whether any concurrent medication, thyroid function, or nutritional gap might be contributing. Tirzepatide is a prescription medicine reviewed by a qualified clinician before and throughout treatment, which means these conversations are part of the service, not an inconvenience.

If you are already on treatment and want to understand the broader hair-change picture, our Mounjaro and hair health page covers the full range of texture, density and scalp changes that have been reported. For those still considering treatment, the Mounjaro overview sets out what the medicine is, how it works, and who it is licensed for. Questions about cost and what private treatment includes are addressed on our Mounjaro price comparison page. And if you would like a GPhC-registered prescriber to assess whether tirzepatide is right for you, start your free consultation, your answers are reviewed by a clinician the same day.