Emergency? If you are soaking through a pad or tampon every hour, feel faint or short of breath, or might be pregnant and are bleeding with pain, call 911 or go to the nearest emergency room. Know the warning signs
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Medication-related causes

Medicines and devices are a common, and often fixable, cause of abnormal bleeding. The I stands for iatrogenic, meaning caused by treatment.

By the AUB editorial teamUpdated September 2026PALM-COEIN: AUB-I

Common culprits

  • Hormonal birth control: breakthrough bleeding, especially in the first months (see bleeding on birth control)
  • Copper IUD: often makes periods heavier and more crampy
  • Menopausal hormone therapy
  • Tamoxifen: can thicken the lining and cause polyps; bleeding while taking it should be evaluated
  • Blood thinners such as warfarin, apixaban, and rivaroxaban, and antiplatelet drugs
  • Medicines that affect ovulation, such as some antipsychotics that raise prolactin

Never stop a blood thinner on your own. Heavy periods on anticoagulation are common and treatable, often with the levonorgestrel IUD or a progestin. Your OB/GYN and the clinician who manages your anticoagulation should decide together.

Evaluation

Even when a medication seems like the obvious explanation, other causes can coexist. Your physician will decide whether you need a pregnancy test, blood count, ultrasound, or biopsy.

Sources

  1. Munro MG, Critchley HOD, Fraser IS; FIGO Menstrual Disorders Committee. The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions. Int J Gynaecol Obstet. 2018;143(3):393–408.

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