Hair Loss and Thinning on Mounjaro and GLP-1 Injections – What You Should Know

By Jaydev Varsani – Clinical Prescribing Pharmacist, Bramley Pharmacy

Many patients using GLP-1 weight-loss medications like Mounjaro (tirzepatide), Wegovy, or Ozempic (semaglutide) have achieved outstanding results — shedding weight, improving blood sugar, and often transforming their confidence and energy.

But some also notice something unexpected: hair shedding or thinning.

If you’ve found more hair in your brush or your hair feels finer since starting a GLP-1, you’re not alone. Although this side effect isn’t especially common, it’s genuine — and worth understanding.

Let’s unpack what’s actually happening, why it occurs, and how to manage or prevent it.

Understanding How Hair Grows

Every strand of hair follows a growth cycle:

• Anagen phase – the active growth period (2–7 years)

• Catagen phase – a short transition stage

• Telogen phase – the resting and shedding phase

At any one time, around 10% of your scalp hair is in the telogen phase.
When your body faces a stressor — whether illness, nutritional deficiency, or rapid weight change — a higher proportion of follicles shift into that resting phase. The result is visible shedding a few months later.

This process is called Telogen Effluvium. It’s usually temporary and fully reversible once the underlying trigger settles.

Does Mounjaro (or Other GLP-1s) Cause Hair Loss?

Hair loss isn’t listed as a standard or “common” side effect on the patient leaflets for GLP-1 agonists, but real-world experience and some trial data suggest there is a link.

• In a tirzepatide (Mounjaro) study, 4–5.7% of users reported hair loss, compared with around 1% in placebo.

• Semaglutide (Ozempic/Wegovy) has also had sporadic reports of similar shedding.

• It’s important to note: rapid weight loss itself can trigger the same phenomenon, even without medication.

So while GLP-1s don’t appear to directly damage hair follicles, the metabolic changes they cause can contribute indirectly.

Why Hair Loss Can Occur on GLP-1 Treatments

There isn’t a single explanation. Several factors can overlap:

1. Rapid Weight Loss

When you lose weight quickly, your body interprets it as a stress event.
This can trigger Telogen Effluvium, a temporary shift in the hair cycle where many follicles rest and shed simultaneously.

It usually begins 2–4 months after major weight change and can last several months.

2. Nutritional Deficiencies

GLP-1 medications reduce appetite and slow digestion.
As a result, some people eat significantly less — and may not meet their nutritional needs.

Hair requires a continuous supply of nutrients to grow properly, including:

• Protein – structural building block of keratin

• Iron and ferritin – essential for oxygen delivery to follicles

• Zinc and selenium – support cell division and repair

• Vitamin D – influences follicle cycling

• Vitamin B12 and folate – important for DNA synthesis

Even mild deficiencies can lead to hair shedding over time.

At Bramley Pharmacy, we offer on-site blood testing that can help identify these potential deficiencies.
Our tests can assess your vitamin D, B12, folate, ferritin, thyroid function, and full blood count, as well as iron, zinc, and protein levels.

This gives a clear picture of what your body might be lacking — allowing tailored advice or supplementation to restore balance and promote regrowth.

3. Hormonal and Metabolic Changes

GLP-1 drugs affect insulin sensitivity, stress hormones, and possibly thyroid hormone activity — all of which can subtly influence the hair cycle.

• Thyroid shifts: even minor changes can lead to diffuse thinning.

• Stress hormones: rapid metabolic change can transiently raise cortisol, which influences follicle shedding.

• Sex hormone balance: as weight normalises and insulin resistance improves, androgen levels change — which can temporarily affect hair growth patterns.

4. Stress and Lifestyle

Major body changes — rapid weight loss, reduced calorie intake, and lifestyle adjustments — create physical and psychological stress. Both can aggravate shedding.

5. Genetic Predisposition

Sometimes GLP-1 therapy reveals an existing trend.
If you have a family history of pattern hair loss, rapid weight changes can make early thinning more visible — even if the drug isn’t the root cause.

How Common Is It?

Current evidence suggests hair loss occurs in roughly 1 in 20 GLP-1 users, though many cases are mild.
Most people will not experience noticeable thinning, and when it does occur, it’s almost always temporary.
As your weight stabilises and nutrition improves, normal growth resumes.

Can It Be Reversed?

Yes — for most people, it is fully reversible.

Once the trigger (rapid weight loss or deficiency) settles, the follicles resume normal cycling. It takes time, though: expect 3–6 months before regrowth is visible, and 6–12 months for full recovery.

What You Can Do to Prevent or Reduce Hair Loss

1. Keep Your Protein Intake Up

Hair is made almost entirely of protein.
If you’re eating less, prioritise protein sources:

• Eggs, fish, lean meat, tofu, pulses, Greek yoghurt, or protein shakes

• Aim for roughly 1g of protein per kg of body weight per day

Protein deficiency is one of the most common contributors to GLP-1-related shedding.

2. Eat a Nutrient-Dense Diet

Even with smaller portions, make every bite count.

Include foods rich in:

• Iron – red meat, lentils, spinach

• Zinc – seeds, nuts, chickpeas

• B vitamins – poultry, dairy, eggs, fortified cereals

• Vitamin D – oily fish, eggs, or supplementation if low

• Omega-3 fatty acids – salmon, flaxseed, walnuts

Our in-pharmacy Wellman and Wellwoman blood profiles can quickly check for these markers.
If anything is out of range, we can guide you on targeted supplementation or dietary changes.

3. Avoid Extremely Rapid Weight Loss

A slower, steadier loss is less likely to trigger Telogen Effluvium.
If you’re losing more than 1–1.5 kg per week, speak to your prescriber. A small dose adjustment may help stabilise your progress and reduce shedding risk.

4. Check Your Thyroid and Iron Levels

Thyroid and iron deficiencies are common, especially in women, and both can mimic or worsen GLP-1-related hair loss.
These are included in our on-site blood panels — results are usually available within 48 hours.

5. Be Gentle With Your Hair

Avoid harsh chemical treatments, tight ponytails, and heat damage.
Use mild shampoos, detangle carefully, and consider caffeine-based or peptide-based scalp serums to stimulate growth.

6. Manage Stress

Good sleep, hydration, and mindfulness techniques all help.
Remember, stress alone can trigger or prolong shedding. Treating your overall wellbeing helps your hair too.

7. Be Patient

Hair regrowth takes time.
Once the body stabilises, it can take several months before you notice new growth — and up to a year for density to normalise.
Stopping your GLP-1 medication prematurely isn’t usually necessary and may reverse your weight-loss gains.

When to Seek Professional Review

You should arrange a review if:

• Hair loss is patchy or accompanied by scalp redness or itching

• You’ve had ongoing shedding for more than six months

• You’re also feeling tired, dizzy, or weak (possible deficiency)

• You’re losing more than 100–150 hairs per day consistently

At Bramley Pharmacy, we can arrange comprehensive blood tests, biotin injections, and nutrient IV drips if needed, to help identify and correct the underlying causes.
You’ll get a clear plan on whether supplementation, dietary change, or medical review is required.

The Takeaway

• Hair loss during GLP-1 treatment is uncommon, but it can happen.

• It’s usually caused by rapid weight loss or nutritional changes, not the medication itself.

• It’s temporary and reversible with the right support.

• Balanced nutrition, adequate protein, slower weight reduction, and self-care are key.

• Blood testing can quickly uncover any hidden deficiencies.

• Most importantly — be patient. Regrowth happens, but it takes time.

If you’re concerned about hair thinning while on Mounjaro, Wegovy, or any GLP-1 treatment, visit Bramley Pharmacy in Ealing for a clinical consultation and blood-testing review.
Our pharmacist-led clinics provide professional, personalised care to get you feeling — and looking — your best again.

References

Drugs.com – Do Ozempic, Wegovy or Mounjaro cause hair loss? (2024).
PubMed – Dermatologic complications of GLP-1 receptor agonists (PMID: 39264502, 2024).
PubMed – Tirzepatide and hair loss: emerging signal review (PMID: 38741261, 2024).
PMC – Semaglutide-associated alopecia: case series and review (PMC11909624, 2024).
Medical News Today – GLP-1 side effects and hair loss (2024).Virta Health – Does Ozempic cause hair loss? (2024).American Academy of Dermatology – Telogen effluvium overview (2023).
Mayo Clinic – Hair loss causes – Telogen effluvium (2023).
NICE – Obesity: identification, assessment and management – GLP-1 agonist use (2023).
Bramley Pharmacy Clinical Services – Private Blood Testing & IV Vitamin Therapy (2025).