Can Mounjaro Affect Your Period?

Last updated: 23 February, 2026

Have you noticed your period is different since starting Mounjaro? Some users have reported changes to their menstrual cycle on their weight loss journey. Some women experience irregular cycles. Others notice changes in how heavy their period is.

Mounjaro works on a hormonal level, mimicking the naturally occurring hormones glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP). This helps regulate blood sugar levels, improve insulin sensitivity, and reduce your appetite.

Because Mounjaro affects hormones, you might wonder if this impacts other aspects of hormonal health. This includes the menstrual cycle.

So let’s explore how Mounjaro can affect the menstrual cycle – and whether changes to your periods are a side effect of Mounjaro.

Can Mounjaro Change Your Menstrual Cycle?

There is currently no evidence that Mounjaro directly affects the menstrual cycle. The medication’s Patient Information Leaflet does not list it as a side effect.

“Some users do report changes to their cycle,” says Abdal Avi, Simple Online Pharmacy’s Chief Clinical Officer. “But the evidence is currently limited. The medication is still relatively new.”

However, Mounjaro (tirzepatide) affects hormones that regulate both appetite and how the body uses glucose. So it is possible that changes in hormone levels and insulin sensitivity could also affect the menstrual cycle.

If your cycle has changed on Mounjaro, it’s probably caused by weight loss from Mounjaro – not the medication itself. Research has found weight and menstruation to be closely linked. Weight loss (and weight gain) can cause changes in oestrogen, a hormone that regulates the menstrual cycle.

Healthy weight loss may improve symptoms of premenstrual syndrome (PMS) and regulate your periods. One clinical study showed the effects of GLP-1 weight loss treatment contributed to more regular periods for women with PCOS (polycystic ovarian syndrome).

Can Mounjaro Stop Periods?

There’s no evidence that Mounjaro stops periods. However, rapid weight loss can.

If your period has stopped, don’t ignore it. It could be a sign your weight loss has been too quick or excessive. Significant weight loss puts stress on the body. In response, the body focuses on essential bodily functions over menstruation and producing hormones like oestrogen.

If you haven’t had your period for three months or more, talk to your doctor. You should also check in with your doctor if you notice any of the following:

• Your cycles are a lot shorter or longer than usual
• You have very heavy or very light periods
• You’re experiencing significant changes in premenstrual symptoms
• You’re getting severe cramping or pain is getting much worse

Your doctor or clinician can determine if Mounjaro – or another factor – is causing these changes.

How Can Weight Loss Affect Your Menstrual Cycle?

Losing weight too fast and being underweight can lower your oestrogen levels. This may cause irregular periods. They could even stop completely.

However, being overweight can raise your oestrogen levels because fat cells also contain oestrogen. This can impact your menstrual cycle and cause heavy periods.

So if you’re overweight or obese, losing weight and maintaining a healthy weight can support hormone balance, including oestrogen and progesterone. This can improve symptoms and make periods more manageable. You might experience:

• Regular Cycles: A healthy body mass index (BMI) can bring your cycle closer to the typical 28-day pattern. Especially if hormonal imbalances from a higher body weight are causing irregular cycles.
• Lighter Periods: Heavy periods are common in women with a higher body weight. Better hormone regulation through weight loss can reduce your flow.
• Less Cramping: Weight loss may reduce inflammation in the body, which can also reduce menstrual cramps. Lower body fat may improve overall circulation, which can ease the discomfort associated with menstruation.
• Improved PMS Symptoms: Losing weight can improve symptoms of PMS, like mood swings, irritability, depression, and anxiety. PMS is often linked to hormonal fluctuations. Weight loss can improve metabolic health, insulin sensitivity, and even serotonin levels in some individuals.

Weight loss may also lead to better mental health overall. Particularly if you combine it with a healthier diet, exercise and sleep habits. These lifestyle changes can improve mood regulation and overall emotional well-being.

Monitoring Menstrual Changes on Mounjaro 

If you’re concerned about Mounjaro and period changes, try tracking your menstrual cycle. It can help you understand how the medication might be affecting your body.

Documenting the following details can provide insights for both yourself and your clinician:

• Your cycle length (the first day of one period to the first day of the next)
• Your flow
• If you’re bleeding between periods
• Any symptoms, including cramping, mood changes, fatigue, bloating and headaches

If you have any concerns about changes to your menstrual cycle while on Mounjaro, let your healthcare provider know.

“What we always advise is that a person reports any changes to their cycle onto their healthcare professional,” Abdal says. “If a person thinks that they might be pregnant…[they should] reach out to us or our Patient Care team or their own GP.”

If you’re a patient with Simple, we’re here for you throughout your weight loss journey. If you have any questions or concerns, get in touch with our Patient Care team on 0141 774 5023.

Key Takeaways

• Changes in Weight Can Influence the Menstrual Cycle. This can vary from changes in flow or cycle length, changes in symptoms and changes in the duration of your cycle.
• Weight Loss May Improve Cycle Regularity. Some studies suggest that Mounjaro could lead to more regular menstrual cycles. This may be particularly true if you experience irregular periods from weight-related hormonal imbalances.
• Irregular Periods and Stopped Periods May Signal You’re Losing Weight to Fast. Let your doctor or a clinician know if you’ve noticed unusual changes to your menstrual cycle.
• Weight Loss May Relieve PMS Symptoms. By improving insulin sensitivity and reducing inflammation, Mounjaro may alleviate PMS symptoms, menstrual cramps, and mood swings. It can also improve insulin sensitivity for people who are insulin resistant, for example those with polycystic ovary syndrome (PCOS).
• Monitor Changes and Discuss With Your Clinician. If you notice any significant changes in your menstrual cycle, like bleeding between periods, keep a note of changes. If you have concerns, discuss these with a healthcare professional.

References 

Package leaflet: Information for the patient (n.d.). Available at: https://www.medicines.org.uk/emc/files/pil.15481.pdf.

Cleveland Clinic. (n.d.). Yes, Weight Loss Can Impact Your Menstrual Cycle. [online] Available at: https://health.clevelandclinic.org/can-weight-loss-affect-your-period.

Pernoud, L. and Schaumberg, M. (2025). I lost weight and my period stopped. How are weight and menstruation linked? [online] The Conversation. Available at: https://theconversation.com/i-lost-weight-and-my-period-stopped-how-are-weight-and-menstruation-linked-244401.

www.medicines.org.uk. (n.d.). Mounjaro KwikPen 2.5mg solution for injection in pre-filled pen – Summary of Product Characteristics (SmPC) – (emc). [online] Available at: https://www.medicines.org.uk/emc/product/15481/smpc.

Zhou, L., Qu, H., Yang, L. and Shou, L. (2023). Effects of GLP1RAs on pregnancy rate and menstrual cyclicity in women with polycystic ovary syndrome: a meta-analysis and systematic review. BMC Endocrine Disorders, 23(1). doi: https://doi.org/10.1186/s12902-023-01500-5.

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