More than 47,000 members of MyLupusTeam take hydroxychloroquine (also known as HCQ and sold under brand names such as Plaquenil), an antimalarial drug also used to manage lupus.

Some MyLupusTeam members wonder whether HCQ can affect their periods. “Has anyone experienced wacky menstrual cycles when starting Plaquenil?” one member asked. “I just started taking it on Tuesday, and my period should be here and it isn’t.”

There isn’t much research on hydroxychloroquine and periods, so it’s hard to give a definitive answer. This article explains what’s known, what’s not known, and other reasons a menstrual cycle may change in people living with lupus.

Hydroxychloroquine and the Treatment of Lupus

Hydroxychloroquine (HCQ) is approved to treat systemic lupus erythematosus (SLE) and chronic discoid lupus erythematosus in adults. Common side effects of HCQ include:

• Nausea
• Vomiting
• Diarrhea
• Stomach pain

Rare but serious side effects can include retinal damage, heart rhythm problems, severe skin reactions, and blood-cell disorders. Menstrual changes aren’t listed as a known side effect in the current prescribing information.

Still, some MyLupusTeam members have connected HCQ with irregular periods in their own experience. They’ve shared comments such as these:

• “I started taking Plaquenil two months ago, and I’ve had three bizarre periods since then. It’s unusual for me, since my periods have always been regular. I’m currently on day 12 of nonstop bleeding, and my last two periods were back to back, only one week apart.”
• “I just started Plaquenil a few weeks ago, and my period has come nine days early — normally it’s 28 days on the dot.”

Others report no effect: “I take Plaquenil, and my menstrual cycles are on point.”

Hydroxychloroquine and Endometriosis Research

Endometriosis occurs when tissue similar to the lining of the uterus grows outside the uterus. It can cause symptoms such as pelvic pain and heavy menstrual bleeding.

Interestingly, a 2021 study found that people with SLE who were continuously treated with HCQ had a lower risk of developing endometriosis. However, this was an observational study, so it shows an association and doesn’t prove that HCQ prevents endometriosis.

More research is needed before HCQ could be considered a treatment or preventive therapy for endometriosis.

Other Lupus Medications and the Menstrual Cycle

If your period changes while you’re taking hydroxychloroquine, HCQ may not be the only possible explanation. Other lupus treatments may affect menstrual bleeding or ovarian function, which can make it harder to tell what is causing the exact change in your cycle.

• Corticosteroids — Corticosteroids, such as prednisone, help reduce inflammation caused by lupus. Some people report menstrual changes with corticosteroid treatment, especially with long-term or high-dose use.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) — NSAIDs, such as ibuprofen or naproxen, are often used to manage pain and inflammation. ACOG says NSAIDs may help control heavy bleeding and relieve menstrual cramps.
• Cyclophosphamide — It can damage the ovaries. In people with lupus, it has been linked to reduced ovarian reserve and ovarian failure, especially with older age and greater treatment exposure.
• Methotrexate — It can cause menstrual dysfunction and affect fertility.

Talk with your rheumatologist if you have concerns about how your lupus medications might affect your menstrual cycle. They can provide guidance based on your treatment plan and symptoms. Do not stop any of your medications without consulting your provider.

Other Causes of Irregular Menstrual Cycles

Menstrual cycle irregularities can occur in people with lupus, whether or not they take HCQ. Lupus and periods can also feel connected because flares, stress, birth control, pregnancy, breastfeeding, and perimenopause can all affect bleeding patterns.

Lupus Activity

Lupus itself may affect reproductive health, but the connection isn’t fully understood. Research suggests that changes in ovarian function in SLE are likely caused by several factors, including the disease and its treatments.

Birth Control

Birth control can also change your period. Combined hormonal pills, patches, and rings may make periods lighter, shorter, and more regular.

Intrauterine devices (IUDs) can affect bleeding differently. Hormonal IUDs may reduce heavy bleeding and cramps but can cause spotting or irregular bleeding during the first three to six months. Copper IUDs may cause heavier bleeding, more cramping, or bleeding between periods, especially at first.

Pregnancy and Breastfeeding

When you’re pregnant, you usually won’t have a period. After giving birth, it may take time for your period to come back. ACOG says if you’re breastfeeding, ovulation may be delayed but usually returns by about six months.

Breastfeeding can work as contraception only under specific conditions. Centers for Disease Control and Prevention (CDC) guidance says all three criteria must be met: no periods, fully or nearly fully breastfeeding with short intervals between feedings, and less than six months postpartum. If any of these don’t apply, talk with your healthcare provider about contraception.

Perimenopause and Menopause

If your periods become less frequent or less predictable, you may be in perimenopause, the transition before menopause. ACOG notes that during perimenopause, it’s common for periods to become lighter, heavier, skipped, or spaced differently.

Lupus-related ovarian effects appear to be complex and uncertain. Among lupus medications, cyclophosphamide has the most established ovarian toxicity, and risk is related to age, cumulative dose, and treatment duration.

When To Talk to Your Doctor

Menstrual cycles vary, but talk with your doctor if you have very heavy bleeding, bleeding between periods, bleeding lasting more than seven days, newly missed periods, or a sudden change from your usual cycle.

Your doctor can help identify possible causes, check for pregnancy or anemia if needed, review your medications, and recommend ways to manage heavy bleeding or cramps.