Does Mounjaro affect periods? What to expect with your cycle

When you start a weight loss medication like Mounjaro, you'll likely observe a range of changes in both your body and your brain.

Chances are, you'll first notice the change in your mind. It just feels... quieter, now that you're no longer obsessing about when you can eat again next and what to eat for your next meal. Then, there's your gut — you start to feel satisfied after eating smaller portions, and that fullness lasts longer than it used to. Next, there are the changes in your eating habits and finally, the weight on the scales and how you look in feel in your clothes.

That said, one unexpected change you may not anticipate is in your menstrual cycle. You may notice that your periods become lighter, shorter and even non-existent. Or, it could go the opposite way and become heavier and longer. But, is an irregular cycle the side effect of the medication itself, or something more complex happening at a physiological level?

Read on for everything you need to know about Mounjaro and your menstrual cycle — including whether it's anything to be concerned about.

Can Mounjaro change your menstrual cycle?

The short answer is, no — there's no research to suggest that GLP-1 medications like Mounjaro directly affect your menstrual cycle. While it can have its fair share of side effects — including bloating, nausea, and other gastrointestinal issues — a disrupted cycle isn't one of them.

That said, there are several ways in which Mounjaro can indirectly affect your period. Understanding why these changes happen can help put your mind at ease during your weight loss journey.

How weight loss itself can affect your menstrual cycle

As you likely know, taking a medication like Mounjaro can lead to significant weight loss — sometimes in short timeframes. As a result, some women notice irregular periods or lose theirs altogether, as an indirect result of Mounjaro's weight loss.

Women need an essential amount of body fat — usually at least 17% — in order to have a regular cycle [1]. However, you don't necessarily have to be 'bodybuilder level' lean to notice these effects.

When your body is under excessive stress due to restrictive eating and overexercising, it can lead to a condition called functional hypothalamic amenorrhea [2]. This is when the hypothalamus (the part of your brain responsible for some reproductive functions, as well as hunger, thirst and perspiration) shuts down the body's sex hormone production.

Rapid weight loss can also lead to period loss, as the body panics and goes into survival mode. If this occurs, you may also notice other side effects such as hair loss, greater irritability and an impaired immune system (meaning you may get sick more often) [3].

Amenorrhea is a serious condition that can lead to long-term health effects like increased risks of osteoporosis and fractures, cardiovascular disease, impaired fertility and mental health issues due to hormonal disruptions [4]. So, if you notice you have missed a cycle, it's important to see your doctor.

Common cycle changes reported on Mounjaro

Weight-related hormonal fluctuations can manifest in many different ways. Some symptoms you may notice are:

Heavier, longer or more intense periods

In rare cases, some women notice that their periods may actually get heavier while on a weight loss treatment. While there's minimal research into this phenomenon, doctors believe this may be because fat loss can lead to the release of estrogen, thickening the uterine lining and leading to a heavier blood flow [5]. This can also result in the period lasting for longer than it used to.

Spotting between periods

Another potential side effect of fluctuating hormone levels is irregular bleeding between periods. While this can be frustrating, it's typically not anything to worry about. However, if you notice a substantial amount of blood (such as what you'd typically expect to see on your period), it's wise to seek medical attention.

Return of periods after a long absence

Weight loss can actually help to regulate menstrual cycles in those who are overweight or obese. Excess body fat can produce high levels of estrogen, which disrupts the normal ovarian feedback system to the brain and can interfere with ovulation [6].

So, by losing body fat and entering a healthier body weight range, some women may actually find they get their period back after a phase of absence. However, if you notice your period is significantly heavier than it was previously, it's important to let your doctor know.

Cycle improvements in people with PCOS

Polycystic ovary syndrome (PCOS) is a condition where the ovaries create excess hormones, such as androgen [7]. This can lead to a range of symptoms, including heavy and painful periods and irregular periods.

As it is a condition that affects the entire endocrine system, an estimated 70-90% of women with PCOS also have insulin resistance. This is when the body blocks glucose from going into cells, which creates more insulin.

As weight loss injections like Mounjaro regulate blood sugar levels, some women with polycystic ovary syndrome find that it improves their insulin sensitivity [8]. This can lead to an improvement in PCOS symptoms, which can in turn affect the menstrual cycle, manifesting in shorter, lighter periods and fewer PMS symptoms. For most women with irregular cycles, this is typically a welcome change!

How Mounjaro may affect ovulation

In some cases, period changes can actually be the result of pregnancy. This can come as a surprise, especially if you've struggled with fertility issues for some time.

While it is not the primary use, there is growing research to suggest that GLP-1 medications can indirectly improve fertility — hence the term 'Ozempic baby.' As Mounjaro can improve insulin sensitivity in women with PCOS and/or insulin resistance, this can lead to more reliable ovulation (and subsequently, egg fertilisation) [9].

There have even been cases of women on oral contraceptives getting pregnant while on weight loss medications. Some theorise that because these medications delay the gastric emptying of the stomach, this can impact the absorption of birth control — making it less effective [10].

If you're not trying to conceive and are starting Mounjaro, you may want to speak to your doctor about additional contraceptive methods.

Do period changes go away with time?

Research shows that most menstrual changes, particularly irregular periods, occur within the first 1 to 3 months of taking Mounjaro and resolve over time [11]. This is because it takes your body time to adjust to weight loss injections like Mounjaro.

Whether you're taking Mounjaro for the first time or are increasing your dose, the start of each phase can be accompanied by side effects that typically subside within 2-3 weeks. In most cases, your menstrual cycle should regulate as your body adjusts to the new dose.

When to seek medical advice about menstrual cycle changes

It's important to note that women's menstrual cycle is a key part of our overall health, and that it can be affected by many things — not just our weight. Therefore, if you notice irregular or missed periods for more than one cycle, it's important to see a medical professional. Other potential red flags to look out for include excessive bleeding, severe abdominal or vaginal pain or bleeding after sex between periods [12].

Managing menstrual changes while on Mounjaro

Menstrual changes can be inconvenient at best and worrying at worst. The last thing you want when you're meant to be enjoying your newfound weight loss is getting an unexpected period when you're on holiday or dealing with a pregnancy scare.

The good news is, you don't have to go through the process alone. With the Juniper Programme, we provide holistic support around the metabolic, lifestyle and hormonal factors that affect all women. This means our expert doctors, nutritionists and health coaches can work with you to achieve improved hormonal balance. Plus, we give you the tools to promote weight loss in a sustainable way — including eating a balanced, healthy diet and designing a fitness routine that works for your body.

At the end of the day, a 'typical' cycle looks different for everyone — and it's normal to go through ebbs and flows. But, with the right support during your Mounjaro weight loss program, you can move back towards predictable cycles and start feeling like your best self again.

Ready to see if Juniper is right for you? You can check your eligibility here.

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