If your period has become irregular or gone missing, your doctor will need to work through various possible explanations, including whether it’s a side effect of one of your medications.
Some medications affect the menstrual cycle directly, by impairing ovulation or altering hormone levels. Others act indirectly, by affecting appetite, stress, sleep, or weight. And some can even have a beneficial effect, such as antihistamines, which can lighten periods and improve premenstrual mood symptoms.
Importantly, any negative effect on your period may not be immediate. It could take weeks or even months for your period to change after starting a new medication.
Types of medications that can cause irregular menstrual cycles
- Hormonal medications such as hormonal birth control, emergency contraception, dienogest (Visanne) for endometriosis, GnRH agonists and antagonists (e.g., Lupron), anti-androgens like spironolactone, menopausal hormone therapy, and even natural progesterone—although properly prescribed progesterone can improve menstrual regularity.
- Psychiatric medications, including some SNRI and SSRI antidepressants (especially paroxetine), tricyclic antidepressants, antipsychotics, and mood stabilizers like valproate.
- ADHD medication (e.g., Vyvanse), primarily via indirect effects such as appetite suppression, weight loss, or sleep disruption.
- Anti-seizure medications, especially valproate, which can promote a PCOS-like hormonal pattern.
- Endocrine medications, including corticosteroids and some diabetes medications, although properly prescribed metformin and GLP-1 agonists can improve ovulation and cycle regularity in PCOS.
- Chemotherapy, which can damage ovarian function and lead to temporary or permanent amenorrhea.
- Opioid-type pain medication, particularly with chronic use, which can suppress FSH and LH.
- Immunosuppressants, either by directly affecting hormones, or by impacting metabolic health.
What to do if your period is affected
If your cycle changed after starting a new medication—even if it was months ago—it’s worth checking with your doctor. Depending on the situation, you might be able to adjust the dose, switch to a different medication, or support your cycle in other ways.
