Saxenda (liraglutide 3.0 mg) is a GLP-1 receptor agonist licensed in the UK for weight management in adults with obesity or overweight with comorbidities. Whilst menstrual cycle changes are not listed as a direct side effect in the Summary of Product Characteristics, some women report alterations to their periods during treatment. These changes typically reflect the body's hormonal response to weight loss rather than a direct pharmacological effect of the medication. Understanding the relationship between Saxenda, weight reduction, and menstrual health can help you recognise normal adaptations and identify when medical review is needed.

Can Saxenda Affect Your Menstrual Cycle?

Saxenda (liraglutide 3.0 mg) is a glucagon-like peptide-1 (GLP-1) receptor agonist licensed in the UK for weight management in adults with a BMI ≥30 kg/m² or 27-<30 kg/m² with weight-related comorbidities, as an adjunct to a reduced-calorie diet and increased physical activity.

Menstrual cycle changes are not listed as an adverse effect in the Summary of Product Characteristics (SmPC), though some women report alterations to their periods after starting treatment.

There is no established direct pharmacological link between liraglutide and menstrual cycle disruption. The medication works primarily by mimicking the incretin hormone GLP-1, which enhances glucose-dependent insulin secretion, suppresses glucagon release, and slows gastric emptying.

However, indirect effects may occur through the metabolic and hormonal changes associated with weight loss itself. Clinical trials show that people taking Saxenda typically lose 5-8% of their body weight over 56 weeks, and this degree of weight change can influence reproductive hormone balance, particularly in those with pre-existing conditions such as polycystic ovary syndrome (PCOS) or hypothalamic amenorrhoea.

It is important to distinguish between medication side effects and the physiological consequences of weight reduction. If you experience menstrual changes whilst taking Saxenda, this may reflect your body's adjustment to a new metabolic state rather than a direct drug effect. Nonetheless, any significant or concerning changes warrant discussion with your GP or prescribing clinician.

Note that treatment should be discontinued after 12 weeks on the 3.0 mg daily dose if you have not lost at least 5% of your initial body weight.

How Weight Loss May Influence Period Regularity

Weight loss—regardless of the method—can have a significant impact on menstrual regularity due to the complex interplay between body composition, energy balance, and reproductive hormones. Adipose tissue is not merely a storage depot; it functions as an active endocrine organ that produces oestrogen through the aromatisation of androgens. Changes in fat mass can therefore alter circulating hormone levels.

In people with obesity, particularly those with PCOS, weight loss often improves menstrual regularity. Excess adiposity is associated with insulin resistance, hyperinsulinaemia, and elevated androgen levels, all of which can disrupt ovulation. Losing 5-10% of body weight can help restore ovulatory cycles and reduce androgen excess. UK clinical guidance supports weight management as an important intervention for people with PCOS experiencing menstrual irregularity.

Conversely, rapid or excessive weight loss can lead to hypothalamic amenorrhoea, a condition where the brain reduces gonadotrophin-releasing hormone (GnRH) secretion in response to perceived energy deficit. This results in low oestrogen levels and absent or irregular periods. Whilst Saxenda promotes gradual weight loss, individuals with lower baseline BMI or those combining medication with very restrictive diets may be at higher risk.

It is therefore essential to approach weight management holistically, ensuring adequate nutrition according to NHS guidance, avoiding overly restrictive diets, monitoring for signs of over-restriction, and maintaining open communication with healthcare providers about any menstrual changes during treatment.

Reported Menstrual Changes in Saxenda Users

Anecdotal reports and patient forums suggest that some people experience menstrual changes after starting Saxenda, though robust clinical trial data specifically examining this outcome are limited. The most commonly reported changes include:

• Irregular cycle length – periods arriving earlier or later than expected

• Changes in flow – heavier (menorrhagia) or lighter (hypomenorrhoea) bleeding

• Missed periods – temporary amenorrhoea, particularly in the first few months

• Premenstrual symptoms – alterations in mood, bloating, or cramping intensity

These changes appear most frequently during the initial months of treatment, coinciding with the period of most rapid weight loss. For many, cycles stabilise after three to six months as the body adapts to a new weight set point.

In people with PCOS, weight loss may improve menstrual regularity by addressing underlying insulin resistance and hyperandrogenism. Some small studies have suggested that GLP-1 receptor agonists might reduce testosterone levels and improve ovulation rates in this population, though it's important to note that Saxenda is not specifically licensed for PCOS management.

It is worth noting that gastrointestinal side effects—nausea, vomiting, and diarrhoea—are common with Saxenda, particularly during dose escalation. Severe or prolonged gastrointestinal symptoms can lead to dehydration and nutritional deficiencies, which may secondarily affect menstrual function. Ensuring adequate hydration and nutrient intake is therefore important for maintaining overall reproductive health.

If you experience menstrual changes on Saxenda, keep a symptom diary noting cycle length, flow characteristics, and any associated symptoms. This information will be valuable when discussing your experience with your healthcare provider.

When to Seek Medical Advice About Period Changes

Whilst some menstrual variation during weight loss is not uncommon, certain changes warrant prompt medical evaluation to rule out underlying pathology or complications. You should contact your GP or prescribing clinician if you experience:

• Absent periods for three months or more (amenorrhoea), particularly if you are not menopausal and pregnancy has been excluded

• Very heavy bleeding requiring pad or tampon changes every hour, or passing large clots

• Bleeding between periods (intermenstrual bleeding) or after intercourse (postcoital bleeding)

• Severe pelvic pain that is new, worsening, or different from your usual menstrual cramping

• Signs of anaemia such as extreme fatigue, breathlessness, palpitations, or pallor

• Suspected pregnancy – remember that weight loss and improved metabolic health may increase fertility, particularly in people with PCOS

Additionally, seek urgent medical attention if you experience:

• Severe, persistent upper abdominal pain (with or without vomiting) which could indicate pancreatitis

• Right upper abdominal pain, fever or yellowing of the skin/eyes, which might suggest gallbladder disease

• Heavy bleeding causing dizziness, fainting or signs of shock

Your clinician will take a thorough history and may arrange investigations including:

• Pregnancy test – to exclude pregnancy as a cause of amenorrhoea

• Full blood count – to assess for anaemia if bleeding is heavy

• Thyroid function tests – as thyroid disorders commonly affect menstruation

• Hormone profile – including FSH, LH, oestradiol, and prolactin if amenorrhoea persists

• Pelvic ultrasound – to evaluate structural causes such as fibroids or ovarian cysts

It is particularly important to seek advice if menstrual changes are accompanied by other concerning symptoms such as unexplained weight loss (beyond that expected with Saxenda), severe abdominal pain, or signs of systemic illness.

Managing Your Period While Taking Saxenda

If you experience menstrual changes whilst taking Saxenda, several practical strategies can help you manage symptoms and support your overall reproductive health during treatment.

Nutritional considerations are paramount. Ensure you are consuming adequate calories to support gradual, sustainable weight loss rather than severe restriction. The NHS recommends a moderate calorie deficit (around 600 kcal/day less than your needs) for safe weight loss. Aim for a balanced diet rich in iron (particularly important if periods are heavy), calcium, and essential fatty acids. Consider discussing your nutritional needs with a dietitian or pharmacist, especially if dietary intake is compromised by Saxenda-related nausea.

Maintain a menstrual diary to track cycle length, flow characteristics, and associated symptoms. This helps identify patterns and provides valuable information for healthcare consultations. Several smartphone applications can facilitate this tracking.

Manage gastrointestinal side effects proactively. Remember that Saxenda is administered by injection once daily, independent of meals. If you experience nausea, consider injecting in the evening, and follow the recommended dose escalation schedule (starting at 0.6 mg and increasing weekly). If side effects are severe, your prescriber may suggest temporarily reducing the dose or pausing treatment.

Consider contraception carefully. If you have been relying on irregular cycles or anovulation as a form of contraception, be aware that weight loss may restore fertility. Discuss reliable contraceptive methods with your GP if pregnancy is not desired. Saxenda must be discontinued if pregnancy occurs or is planned.

Continue regular cervical screening as per your national programme guidelines, and attend routine gynaecological appointments. Weight loss and metabolic improvement do not eliminate the need for preventive healthcare.

Finally, communicate openly with your healthcare team. Your prescriber should be informed of significant menstrual changes, as this may influence treatment decisions or prompt investigation for other causes. Most menstrual changes associated with weight loss are temporary and resolve as your body adjusts, but ongoing monitoring ensures any concerning developments are addressed promptly.

If you suspect any side effects from Saxenda, report them via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

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