Mounjaro Hair Loss: Causes & Prevention

Yes, Mounjaro can cause hair loss.

According to studies, it is estimated that around 10% of users experience hair loss with Mounjaro.

Hair loss itself is not a direct result of medication, but it is due to the rapid rate of weight loss.

Hair loss and hair thinning are usually temporary and resolve as the body adjusts to significant weight fluctuations or a reduced calorie intake.

It is a short-term effect known as telogen effluvium, which often improves once your weight and nutrition levels stabilise.

To see why Mounjaro can cause hair loss, it helps to understand the different stages of the hair growth cycle.

Your hair naturally cycles through four growth phases.

Anagen phase: The active growth stage, lasting around 2 to 8 years. During this time, hair follicles produce new strands that continue to grow until they are cut or reach the end of their life cycle.

Catagen phase: A short transitional stage of about 2 weeks, where hair follicles shrink and growth slows down.

Telogen phase: The resting stage, lasting around 2 to 3 months. After significant or rapid weight loss, more hairs than usual can enter this phase, leading to noticeable thinning or shedding.

Shedding phase: The final stage, where old hairs are released from the scalp, making way for new ones to grow.

Rapid weight loss can disrupt this balance, pushing more follicles into the telogen (resting) phase, which leads to increased shedding. This is known as telogen effluvium.

Telogen Effluvium

• Hair loss after a stressful event such as rapid weight loss, is known as Telogen Effluvium
• Many hair follicles enter the resting phase earlier than usual, causing hair loss
• Most of the time, hair shedding stops within 6-12 months after stress levels and weight loss have stabilised

In most cases, hair growth returns to its usual pattern once the body adapts.

The most common reasons include:

Stress

Starting a new medication, making lifestyle changes, or experiencing rapid weight loss can all be perceived by the body as a form of stress.

This is known as telogen effluvium, when stress pushes hair follicles into a resting phase, causing hair to shed.

Hair shedding related to weight loss has been observed in individuals who lose around 15% of their body weight.

Nutritional deficiencies

Rapid weight loss or a significant reduction in food intake can cause deficiencies in key nutrients such as protein, iron, zinc, and biotin, all of which are essential for healthy hair growth.

When these nutrients are lacking, hair follicles may enter the resting phase, leading to increased shedding (telogen effluvium). Maintaining a balanced, nutrient-rich diet can help minimise hair loss.

Hormone Imbalance

Weight loss and metabolic changes can affect thyroid hormones, insulin, and sex hormones.

Changes in these hormone levels can make hair follicles enter the resting phase sooner than usual, slowing new growth (telogen effluvium). This effect generally eases as hormone balance returns to normal.

Some hormonal changes that can contribute to hair loss during weight loss include:

• Reduced oestrogen: a key female sex hormone that supports healthy hair growth.
• Increased cortisol: a stress hormone that can disrupt the normal hair growth cycle.
• Thyroid hormone imbalances: affecting hormones that regulate metabolism, energy levels, and overall body function.

While hair loss can occur during Mounjaro treatment, there are steps you can take to prevent this from happening and help support regrowth.

Seek advice from your doctor or pharmacist if your shedding is severe, persists for several months, or is accompanied by other symptoms such as fatigue, unusual weight changes, or signs of nutritional deficiencies.  

Early guidance can help identify any underlying issues and support your hair and overall health. 

Hair loss can happen while taking Mounjaro. This is usually due to reduced calorie intake, stress on your body from rapid weight loss, or changes in hormones, rather than the medication itself directly.

Most hair shedding is not permanent and improves as the body adjusts. Paying attention to nutrition, your hair care routine, and overall health can support recovery, and it is important not to forget that hair growth takes time.

Most people see improvement within a few months once the body adapts to weight loss and any deficiencies or hormonal imbalances are corrected.