Many women taking GLP-1 receptor agonists for diabetes or weight management wonder whether these medications might affect their menstrual cycle. Whilst GLP-1 medications such as semaglutide (Ozempic, Wegovy) and liraglutide (Victoza, Saxenda) do not directly target reproductive hormones, the substantial weight loss and metabolic changes they produce can indirectly influence period regularity. Understanding this connection helps women anticipate potential menstrual changes and recognise when medical review is needed. This article explores how GLP-1 medications work, why weight loss may affect your period, and when to seek advice from your GP.

What Are GLP-1 Medications and How Do They Work?

Glucagon-like peptide-1 (GLP-1) receptor agonists are a class of medications originally developed for managing type 2 diabetes, though some are now also licensed for weight management. In the UK, semaglutide (Ozempic) and liraglutide (Victoza) are MHRA-approved for type 2 diabetes, while semaglutide (Wegovy) and liraglutide (Saxenda) are specifically licensed for weight management. These drugs work by mimicking a naturally occurring hormone that regulates blood sugar and appetite.

GLP-1 medications exert their effects through several mechanisms. They stimulate insulin secretion from the pancreas when blood glucose levels are elevated, helping to control blood sugar. Simultaneously, they suppress glucagon release, a hormone that raises blood glucose. Perhaps most notably for weight management, GLP-1 receptor agonists slow gastric emptying and act on appetite centres in the brain, leading to increased satiety and reduced food intake. This combination of effects typically results in significant weight loss over time.

These medications are administered via subcutaneous injection, with dosing schedules varying from daily to weekly depending on the specific formulation. Common side effects include nausea, vomiting, diarrhoea, and constipation, particularly during the initial titration period. More serious but rare adverse effects can include pancreatitis (seek urgent medical attention for severe, persistent abdominal pain, especially if accompanied by vomiting) and gallbladder disease. If you experience concerning symptoms, stop taking the medication and contact your healthcare provider immediately.

NICE guidelines recommend specific GLP-1 receptor agonists as part of a comprehensive approach to diabetes management (NG28) and, in specific circumstances, for weight management in individuals with obesity or overweight with comorbidities (TA875 for semaglutide, TA664 for liraglutide).

Whilst GLP-1 medications do not directly target reproductive hormones, the substantial metabolic and weight changes they induce can have indirect effects on menstrual function, which warrants careful consideration for women of reproductive age. These medications are not recommended during pregnancy or breastfeeding.

Why Weight Loss May Influence Period Regularity

The relationship between body weight and menstrual function is well established in medical literature. Significant weight changes—whether loss or gain—can disrupt the delicate hormonal balance that regulates the menstrual cycle. When taking GLP-1 medications, many women experience substantial weight reduction, which can subsequently affect period regularity through several physiological mechanisms.

Adipose tissue (body fat) is not metabolically inert; it actively produces oestrogen through the conversion of androgens via the enzyme aromatase. When body fat decreases rapidly, oestrogen levels may fluctuate, potentially leading to irregular periods, lighter bleeding, or temporary amenorrhoea (absence of menstruation). Conversely, for women with polycystic ovary syndrome (PCOS) or obesity-related menstrual irregularities, weight loss can actually restore ovulatory cycles and improve period regularity. This paradoxical effect depends on the individual's baseline metabolic and hormonal status.

The hypothalamic-pituitary-ovarian axis, which governs reproductive function, is sensitive to energy availability. Rapid weight loss can signal energy deficiency to the hypothalamus, potentially suppressing gonadotropin-releasing hormone (GnRH) secretion. This, in turn, reduces follicle-stimulating hormone (FSH) and luteinising hormone (LH) production, which are essential for ovulation and regular menstrual cycles. This mechanism can lead to functional hypothalamic amenorrhoea if weight loss is rapid or energy intake is inadequate. Additionally, changes in insulin sensitivity associated with weight loss and improved glycaemic control can alter the hormonal milieu, particularly in women with insulin resistance.

It is important to note that menstrual disturbances are not listed as direct side effects of GLP-1 receptor agonists in UK product information. Rather, any menstrual changes observed are most likely secondary to the metabolic improvements and weight reduction these medications facilitate. Individual responses vary considerably based on baseline weight, rate of weight loss, underlying conditions such as PCOS, and overall metabolic health. If your period is delayed, consider taking a pregnancy test as a first step.

Managing Menstrual Changes While Taking GLP-1 Medications

If you experience menstrual changes whilst taking GLP-1 medications, several practical strategies can help you manage these alterations effectively. Tracking your menstrual cycle using a diary or smartphone application is invaluable for identifying patterns and providing accurate information to your healthcare provider. Record the timing, duration, and characteristics of your periods, along with any associated symptoms such as pain, mood changes, or unusual bleeding.

Maintaining adequate nutrition is crucial during weight loss. Whilst GLP-1 medications reduce appetite, ensuring sufficient intake of essential nutrients supports overall hormonal health. Focus on:

• Protein-rich foods to preserve lean muscle mass during weight loss

• Iron-containing foods (red meat, leafy greens, fortified cereals) to prevent anaemia, particularly if periods become heavier

• Calcium and vitamin D for bone health, as oestrogen fluctuations can affect bone density

• Healthy fats including omega-3 fatty acids, which support hormone production

For women using hormonal contraception, the Faculty of Sexual and Reproductive Healthcare (FSRH) advises that semaglutide and liraglutide do not reduce hormonal contraceptive efficacy. However, if you experience vomiting within 3 hours of taking an oral contraceptive pill, or severe diarrhoea lasting more than 24 hours, follow the missed pill guidance in the patient information leaflet. Using effective contraception is important while taking GLP-1 medications, as they are not recommended during pregnancy.

Gradual dose titration of GLP-1 medications, as recommended by prescribing guidelines, helps minimise gastrointestinal side effects and may help your body adjust to metabolic changes more gradually. Your prescriber should follow established protocols for increasing doses slowly over several weeks. If menstrual changes are particularly troublesome, discussing the rate of weight loss with your healthcare provider may be appropriate.

Some women find that lifestyle modifications complement their medication regimen. Regular moderate exercise supports hormonal balance, though excessive exercise combined with rapid weight loss can exacerbate menstrual irregularities. Stress management techniques such as mindfulness or cognitive behavioural approaches may also prove beneficial, as psychological stress can independently affect menstrual function.

When to Speak to Your GP About Period Changes

Whilst some menstrual variation during significant weight loss may be expected, certain symptoms warrant prompt medical evaluation. You should contact your GP if you experience:

• Absence of periods for three consecutive cycles (amenorrhoea) if you previously had regular menstruation

• Unusually heavy bleeding (soaking through a pad or tampon every hour for several consecutive hours) or passing large clots

• Bleeding between periods or after intercourse, which requires investigation regardless of medication use

• Severe pelvic pain that differs from typical menstrual cramping

• Symptoms of anaemia including persistent fatigue, breathlessness, palpitations, or pallor

Seek urgent medical help via NHS 111 or A&E for very heavy bleeding with dizziness or fainting, or severe abdominal pain that could indicate complications such as pancreatitis.

Your GP will take a comprehensive history and may perform examinations or investigations to exclude other causes of menstrual irregularity. NICE Clinical Knowledge Summary (CKS) on Amenorrhoea recommends that investigation should include pregnancy testing (essential first step), assessment of thyroid function, prolactin levels, and potentially FSH and LH measurements. Pelvic ultrasound may be indicated if structural abnormalities are suspected.

For women with pre-existing conditions such as PCOS, endometriosis, or fibroids, discussing how GLP-1 medications might interact with these conditions before starting treatment is advisable. Similarly, if you are planning pregnancy, inform your healthcare provider. For semaglutide, treatment should be discontinued at least 2 months before conception attempts. For liraglutide, discontinue when pregnancy is planned. Neither medication is recommended during pregnancy or breastfeeding.

If you have concerns about fertility, particularly if you are experiencing amenorrhoea, seek medical advice promptly. Whilst weight loss often improves fertility in women with obesity-related anovulation, prolonged absence of periods requires investigation. Your GP may refer you to gynaecology or endocrinology services if menstrual disturbances persist despite appropriate management, or if there are features suggesting underlying hormonal disorders beyond the effects of weight change.

If you experience any suspected side effects from GLP-1 medications, you can report them through the MHRA Yellow Card scheme, which helps monitor medication safety.

Frequently Asked Questions