Noticing hair loss on Mounjaro or Wegovy? Learn why hair shedding happens during weight loss, how long it lasts, whether it grows back and what you can do.
Can Mounjaro or Wegovy cause hair loss?
Yes, some people notice increased hair shedding while taking Mounjaro or Wegovy. Hair loss is listed as a possible side effect of both medicines.
But there is an important point that often gets lost online.
In most cases, the hair loss is caused by the weight loss itself, not directly by the medicine.
Losing a significant amount of weight in a relatively short time places stress on the body. This can trigger a temporary type of hair shedding called telogen effluvium.
The reassuring news is that this type of hair loss is:
- Usually temporary
- Not scarring, so the hair follicles are not permanently damaged
- Typically followed by regrowth once the body adjusts
This guide explains why it happens, how common it is, how long it lasts, what you can do to reduce it, and when it is worth getting checked.
How common is hair loss on weight loss injections?
Hair loss was reported in the clinical trials of both medicines, but it affected a minority of participants.
- In the main trial of tirzepatide (Mounjaro) for weight management, hair loss was reported by around 5% of people taking the medicine, compared with around 1% of those taking placebo.
- In the main trial of semaglutide (Wegovy), hair loss was reported by around 3% of people taking the medicine, compared with around 1% taking placebo.
The patient information leaflets for both medicines list hair loss as a common side effect, meaning it may affect up to 1 in 10 people.
Hair loss appears to be more likely in people who lose a larger amount of weight, or who lose weight more quickly. This supports the view that the weight loss, rather than the drug itself, is the main driver.
Why does weight loss cause hair shedding?
To understand this, it helps to know how hair grows.
The hair growth cycle
Each hair follicle cycles through three main phases:
- Growth phase (anagen): lasts several years. Most of the hairs on your head are in this phase at any time.
- Transition phase (catagen): a short phase lasting a few weeks.
- Resting phase (telogen): lasts around three months, after which the hair is shed and a new hair begins to grow.
It is normal to lose around 50 to 100 hairs a day as part of this cycle.
What is telogen effluvium?
When the body experiences a significant physical stress, a larger than usual number of hairs can shift from the growth phase into the resting phase at the same time.
Around two to four months later, those hairs are shed together.
This is called telogen effluvium.
Common triggers include:
- Rapid or significant weight loss
- Reduced calorie or protein intake
- Major surgery
- Serious illness or high fever
- Childbirth
- Severe emotional stress
- Nutritional deficiencies
Weight loss with Mounjaro or Wegovy can involve two of these triggers at once: a substantial reduction in body weight and a marked drop in food intake.
The same type of hair shedding is well recognised after weight loss surgery and after crash dieting, long before these medicines existed.
What does it look like?
Telogen effluvium usually causes diffuse thinning across the whole scalp, rather than bald patches.
You may notice:
- More hair in the shower drain or on your hairbrush
- More hair on your pillow or clothes
- A thinner ponytail
- A wider parting
- Thinning around the temples
It can be distressing, but the amount of hair lost often looks worse to you than it does to others.
It does not usually cause:
- Complete baldness
- Smooth, round bald patches
- Scarring, pain or soreness of the scalp
- Loss of eyebrows or eyelashes
If you notice any of these, see your GP, as there may be another cause.
When does it start and how long does it last?
A typical pattern is:
- Months 0 to 2: treatment starts and weight begins to fall. Hair looks normal.
- Months 2 to 4: increased shedding begins.
- Months 4 to 6: shedding may continue, and is often at its most noticeable.
- Month 6 onwards: shedding gradually slows as the body adapts, and new hairs begin to grow.
For most people, shedding settles within around six months of starting.
Because hair grows slowly, at roughly one centimetre a month, it can take several more months for new growth to become visible and for hair to feel thicker again.
If your weight continues to fall rapidly for a long period, shedding may last longer.
Does the hair grow back?
In most cases, yes.
Telogen effluvium does not destroy hair follicles. Once the trigger has passed and your body has adjusted to its new weight and nutritional intake, the follicles return to their normal cycle.
You may notice short, fine "baby hairs" appearing along your hairline and parting. This is a sign of regrowth.
Regrowth is more likely to be complete if you:
- Eat enough protein and overall nutrition
- Correct any deficiencies
- Lose weight at a steady rather than extreme pace
- Avoid further physical stress on the hair
How to reduce hair loss on Mounjaro or Wegovy
You cannot always prevent telogen effluvium, but you can reduce the risk and support recovery.
1. Eat enough protein
Hair is made of a protein called keratin.
When your appetite is low, it is easy to under-eat protein, and the body will prioritise essential organs over hair growth.
Include a protein source at every meal, such as eggs, fish, chicken, lean meat, Greek yoghurt, cottage cheese, tofu, beans or lentils.
Our guide on what to eat on Mounjaro or Wegovy includes practical meal ideas.
2. Do not under-eat
Weight loss injections are intended to help you eat less, not to help you eat almost nothing.
Very low food intake is one of the strongest triggers for hair shedding. If you are struggling to eat, speak to your prescriber, as your dose may need to be reviewed.
3. Aim for steady weight loss
Faster is not better where your hair is concerned.
Do not increase your dose more quickly than prescribed, and tell your prescriber if you are losing weight very rapidly. Our article on how much weight you can lose on Mounjaro or Wegovy describes a realistic pace.
4. Check for nutritional deficiencies
Several nutrients are important for healthy hair growth, including:
- Iron (low iron stores are a common cause of hair thinning, particularly in women who have periods)
- Vitamin D
- Vitamin B12
- Zinc
- Folate
If your hair loss is significant or prolonged, ask your GP about blood tests. These may include a full blood count, ferritin (iron stores), thyroid function, vitamin D and B12.
Do not take high-dose supplements without advice. Too much of certain nutrients, such as vitamin A, selenium or zinc, can make hair loss worse or cause other problems.
5. Be gentle with your hair
While your hair is shedding more than usual:
- Avoid tight hairstyles such as tight ponytails, buns and braids
- Limit heat styling
- Avoid harsh chemical treatments, bleaching and perming
- Use a wide-toothed comb and avoid brushing wet hair roughly
- Use a mild shampoo and conditioner
Washing your hair does not cause hair loss. The hairs that fall out in the shower were already due to be shed.
6. Look after your general health
Poor sleep, high stress and illness can all contribute to shedding. Stay hydrated, keep active and look after your wellbeing.
Strength training also helps protect muscle during weight loss. Read more in our article on weight loss injections and muscle loss.
Do hair supplements work?
Hair supplements are heavily marketed to people on weight loss injections.
The evidence is mixed.
- If you have a deficiency, correcting it can help.
- If you do not have a deficiency, there is little good evidence that extra vitamins improve hair growth.
Biotin is one of the most popular hair supplements, but true biotin deficiency is rare, and evidence that it helps people with normal levels is weak. High-dose biotin can also interfere with some blood tests, including thyroid and heart tests. Always tell your doctor if you take it.
A standard multivitamin may be reasonable if your food intake is low, but it is best to discuss this with a pharmacist or your prescriber.
Can you use minoxidil or other hair loss treatments?
Telogen effluvium usually resolves by itself, so specific hair loss medicines are often not needed.
However, some people have another type of hair loss at the same time.
Male and female pattern hair loss (androgenetic alopecia) is very common, runs in families and develops gradually. Weight loss can sometimes make underlying pattern hair loss more noticeable.
In men, pattern hair loss typically causes a receding hairline and thinning at the crown. In women, it usually causes gradual thinning along the parting.
Treatments such as minoxidil and, for men, finasteride are used for pattern hair loss. They are not specifically licensed for hair shedding caused by weight loss.
If you think you may have pattern hair loss, you can read more in our guides:
You can also view SynovaMed's full range of treatments. Always tell the prescriber about all the medicines you are taking, including your weight loss injection.
Should you stop Mounjaro or Wegovy because of hair loss?
For most people, no.
Hair shedding linked to weight loss is usually temporary, and stopping treatment will not make the hairs that are already in the resting phase stay in place.
Stopping treatment may also lead to weight regain. See what happens when you stop Mounjaro or Wegovy.
That said, how you feel about your hair matters. If hair loss is causing you significant distress, speak to your prescriber. Options may include:
- Reviewing your diet and protein intake
- Slowing the rate of weight loss
- Staying on your current dose rather than increasing
- Arranging blood tests through your GP
Do not stop or change your dose without discussing it first.
When should you see a doctor?
See your GP if:
- Hair loss is sudden or severe
- You have bald patches
- Your scalp is itchy, sore, red, scaly or scarred
- You are losing eyebrows, eyelashes or body hair
- Shedding continues for more than six months
- You have other symptoms, such as extreme tiredness, feeling cold, heavy periods, or unexplained changes in weight or mood
- Hair loss is affecting your mental wellbeing
Other causes of hair loss include thyroid problems, iron deficiency anaemia, hormonal changes including the menopause, certain medicines and autoimmune conditions such as alopecia areata. These need to be identified and treated separately.
Hair loss, hormones and other factors
Weight loss does not happen in isolation, and several other factors can affect your hair at the same time:
- Menopause and perimenopause can cause hair thinning. See our guide to weight loss injections, menopause and HRT.
- Polycystic ovary syndrome (PCOS) can cause scalp hair thinning.
- Stopping or changing hormonal contraception can trigger shedding.
- Thyroid disorders commonly affect hair.
- Stress and major life events are well-known triggers.
If you are unsure what is causing your hair loss, your GP is the best person to help.
How SynovaMed can help
If you are taking Mounjaro or Wegovy through SynovaMed and are concerned about hair loss, please mention it in your check-in or contact our team.
We can review your dose, your rate of weight loss and your diet, and advise whether you should speak to your GP about blood tests.
For an overview of other possible side effects, read our guide to weight loss injection side effects.
Frequently Asked Questions
Does Mounjaro cause hair loss?
Hair loss is listed as a possible side effect of Mounjaro. In most cases, it is thought to be caused by significant weight loss and reduced food intake rather than a direct effect of the medicine.
Does Wegovy cause hair loss?
Hair loss is also listed as a possible side effect of Wegovy and is thought to be mainly linked to the weight loss itself.
How common is hair loss on weight loss injections?
In the main clinical trials, hair loss was reported by around 3% to 5% of people taking these medicines, compared with around 1% of people taking placebo.
Will my hair grow back after Mounjaro or Wegovy hair loss?
In most cases, yes. Hair shedding caused by weight loss is usually temporary and the hair follicles are not permanently damaged.
How long does hair loss last on Mounjaro?
Shedding typically begins two to four months after starting and settles within around six months, although regrowth takes several more months to become visible.
How can I stop my hair falling out on Wegovy?
Eat enough protein, avoid under-eating, aim for steady weight loss, check for deficiencies and treat your hair gently. Speak to your prescriber if shedding is severe.
Should I take biotin for hair loss on Mounjaro?
There is little evidence that biotin helps unless you are deficient, which is rare. It can also interfere with some blood tests. Speak to a pharmacist or your GP before taking it.
Is hair loss worse on Mounjaro or Wegovy?
Trial figures were slightly higher for tirzepatide, which also produced greater average weight loss. The amount and speed of weight loss appears to matter more than which medicine you take.
Does Ozempic cause hair loss?
Ozempic contains semaglutide, the same active ingredient as Wegovy, and hair loss has also been reported by people taking it.
Should I stop my weight loss injection if my hair is thinning?
Usually not, but do discuss it with your prescriber. Stopping treatment will not immediately stop the shedding and may lead to weight regain.
Can low iron cause hair loss during weight loss?
Yes. Low iron stores are a common cause of hair thinning, particularly in women. Your GP can check this with a blood test.
The bottom line: hair loss on Mounjaro or Wegovy
Hair shedding during treatment with Mounjaro or Wegovy can be upsetting, but it is usually temporary.
It is most often a reaction to significant weight loss and reduced food intake, not a sign that the medicine is damaging your hair.
To give your hair the best chance:
Eat enough protein.
Do not under-eat.
Lose weight steadily, not as fast as possible.
Check for iron and vitamin deficiencies if shedding is significant.
Be gentle with your hair.
See your GP if you have bald patches, scalp symptoms or shedding that lasts longer than six months.
For most people, shedding slows within a few months and the hair gradually recovers.
Medical Disclaimer
This article is intended for general educational purposes and does not replace personalised medical advice, diagnosis or treatment. Hair loss has many possible causes, and persistent or severe hair loss should be assessed by a healthcare professional. Mounjaro, Wegovy and other prescription weight-management medicines are not suitable for everyone. Do not stop or change your medicine, or start supplements or hair loss treatments, without seeking appropriate advice.