Myfembree Side Effects: What to Expect and When to Call Your Doctor

What You Should Know About Myfembree Side Effects

Myfembree (Relugolix/Estradiol/Norethindrone Acetate) is a once-daily oral medication used to treat heavy menstrual bleeding from uterine fibroids and moderate to severe endometriosis pain in premenopausal women. Like all medications, it comes with potential side effects — some mild and manageable, others serious enough to require immediate medical attention.

This guide covers the most common and serious side effects of Myfembree based on FDA labeling, so you know what to expect and when to reach out to your healthcare provider.

What Is Myfembree? (Quick Overview)

Myfembree combines three active ingredients:

• Relugolix (40 mg) — a GnRH receptor antagonist that reduces estrogen production
• Estradiol (1 mg) — an estrogen that provides "add-back" therapy
• Norethindrone Acetate (0.5 mg) — a progestin that works with estradiol to reduce hypoestrogenic side effects

The add-back therapy is designed to lower the risk of bone loss and other estrogen-deprivation side effects. For a deeper look at what Myfembree is and how it's used, see our full guide.

Common Side Effects of Myfembree

The following side effects were reported in clinical trials and are generally mild to moderate. Most improve over the first few weeks or months of treatment:

• Headache — One of the most frequently reported side effects
• Hot flashes — Related to estrogen suppression, though add-back therapy helps reduce severity
• Night sweats — Often occurs alongside hot flashes
• Excessive sweating (hyperhidrosis)
• Hair loss (alopecia) — Usually mild thinning rather than significant loss
• Nausea — May improve if you take Myfembree with food
• Dizziness
• Fatigue
• Back pain
• Decreased libido — Related to hormonal changes
• Menstrual cycle changes — Irregular bleeding, spotting, or changes in flow are common, especially in the first few months

Many women find that these side effects are much more manageable than the symptoms of untreated fibroids or endometriosis. Talk to your doctor if any of these become bothersome — there are often ways to manage them.

Serious Side Effects of Myfembree

While less common, Myfembree does carry risks of more serious side effects. Some require immediate medical attention.

⚠️ Boxed Warning: Thromboembolic Events

Myfembree's most serious warning relates to blood clots and vascular events. The estrogen and progestin components increase the risk of:

• Deep vein thrombosis (DVT) — blood clots in the legs
• Pulmonary embolism (PE) — blood clots in the lungs
• Stroke
• Heart attack (myocardial infarction)

This risk is highest in women who:

• Are over 35 and smoke
• Have uncontrolled high blood pressure
• Have a history of blood clots
• Have obesity, dyslipidemia, or vascular disease

Call 911 or go to the emergency room immediately if you experience:

• Sudden severe headache
• Chest pain or shortness of breath
• Leg swelling, pain, or redness
• Sudden numbness or weakness on one side of the body
• Vision changes or difficulty speaking

Bone Loss

Myfembree can cause a decrease in bone mineral density. This is why treatment is limited to 24 months — prolonged use may lead to bone loss that is not fully reversible. Your doctor may order a bone density scan (DEXA scan) before or during treatment, especially if you have other risk factors for osteoporosis.

Other Serious Side Effects

• Increased blood pressure — Your doctor should monitor your blood pressure regularly
• Gallbladder disease or liver problems — Report any yellowing of skin/eyes, dark urine, or upper abdominal pain
• Mood changes — Including depression and, in rare cases, suicidal thoughts. Tell your doctor about any significant mood changes
• Elevated blood sugar — Important to monitor if you have diabetes or prediabetes
• Elevated cholesterol and triglycerides
• Allergic reactions — Anaphylaxis, hives, or swelling (rare but serious)
• Uterine fibroid prolapse or expulsion — In women with submucosal fibroids

Specific Populations: Who Needs Extra Caution

Women Over 35 Who Smoke

If you smoke and are over 35, the risk of serious cardiovascular events with Myfembree is significantly higher. Your doctor may recommend quitting smoking before starting this medication or may suggest an alternative treatment.

Women with Cardiovascular Risk Factors

If you have high blood pressure, diabetes, high cholesterol, or obesity, your doctor will carefully weigh the risks and benefits before prescribing Myfembree.

Pregnancy and Breastfeeding

Myfembree is contraindicated in pregnancy. A pregnancy test is required before starting treatment. Myfembree is not a contraceptive, so you'll need to use non-hormonal birth control (such as condoms or a copper IUD) while taking it. Breastfeeding is not recommended while on Myfembree, as Relugolix passes into breast milk.

Women at Risk for Osteoporosis

If you already have low bone density or risk factors for osteoporosis, your doctor may recommend extra monitoring or an alternative treatment. Myfembree is contraindicated in women with known osteoporosis.

How to Manage Common Side Effects

Here are some practical tips for dealing with the most common Myfembree side effects:

• Hot flashes and night sweats: Dress in layers, keep your bedroom cool, use a fan, and avoid spicy foods, alcohol, and caffeine before bed
• Headaches: Stay hydrated, manage stress, and ask your doctor about safe pain relievers
• Nausea: Try taking Myfembree with food. Eat smaller, more frequent meals
• Hair thinning: Use gentle hair products and avoid excessive heat styling. This usually improves after stopping the medication
• Fatigue: Prioritize sleep, stay active with light exercise, and talk to your doctor if it's severe
• Mood changes: Keep a mood journal, stay connected with supportive people, and reach out to your doctor if you notice depression or anxiety worsening

Don't stop taking Myfembree without talking to your doctor first, even if side effects are bothering you. Your provider may be able to adjust your treatment plan or help you manage symptoms more effectively.

Final Thoughts

Most women who take Myfembree experience mild side effects that improve over time. However, because of the boxed warning about blood clots and the risk of bone loss, it's important to stay in close contact with your doctor throughout treatment.

Know the warning signs of serious side effects, keep up with your scheduled appointments, and don't hesitate to call your doctor if something doesn't feel right.

If you're ready to start Myfembree, use Medfinder to find a pharmacy near you that has it in stock. And for more information about what Myfembree is and how it works, check out our other guides.