Can Mounjaro Affect Your Period?

Have you noticed your period is different since starting Mounjaro? Some users have reported changes to their menstrual cycle on their weight loss journey – including how often they get their period and how heavy it 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, some users have questioned how it might impact 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. It’s not listed as a side effect on the medication’s patient information leaflet.

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

If your cycle has changed on Mounjaro, the likely cause is weight loss triggered by Mounjaro – not the medication itself. Research has found that weight and menstruation are 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 and regulate your periods. One clinical study showed the effects of GLP-1 weight loss treatment contributed to more regular periods for women with polycystic ovarian syndrome (PCOS).

Can Mounjaro Stop Periods?

There’s no evidence that Mounjaro stops periods. However, fast or significant weight loss can.

If your period has stopped, don’t ignore it. The technical term for a stopped period is “amenorrhoea”. It can be a sign your weight loss has been too quick or excessive. Significant weight loss puts stress on the body. In response, the body prioritises essential bodily functions over menstruation and producing hormones like oestrogen.

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

• Your cycles are significantly shorter or longer than usual
• You have unusually heavy or light periods
• You’re experiencing significant changes in premenstrual symptoms
• You’re experiencing severe cramping or changes in the intensity of menstrual pain

Your doctor or a clinician can help determine if these changes are caused by the effects of Mounjaro, or if there’s another contributing factor.

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 – and 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 help balance hormones like 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 irregularities were caused by hormonal imbalances from a higher body weight.

• 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 it’s accompanied by better diet, exercise and sleep patterns. 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, tracking your menstrual cycle is a great way to 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
• 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. 

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 Help Regulate Cycles. Some studies suggest that Mounjaro could lead to more regular menstrual cycles, particularly for individuals who experience irregular periods due to 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.

• Monitor Changes and Discuss With Your Clinician: If you notice any significant changes in your menstrual cycle while taking Mounjaro, keep a note of changes. If you have concerns, discuss these with a healthcare professional.

Clinically reviewed by Richard Wood, GPhC reg: 2078802

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#gref.

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.