Published: 7 December 2023


Discuss possible effects on uterine bleeding in people taking oral anticoagulant therapy

Published: 7 December 2023
Prescriber Update 44(4): 74–76
December 2023

Key messages

  • Inform patients they may experience new or worsened abnormal uterine bleeding when starting and during oral anticoagulant therapy.
  • Pre-menopausal patients and those with a history of abnormal uterine bleeding may be at a higher risk of abnormal uterine bleeding with oral anticoagulant use.

From August 2022 to February 2023, Medsafe issued a Monitoring Communication to gather more information about abnormal uterine bleeding with oral anticoagulants.

This article aims to increase awareness about this specific type of bleeding with oral anticoagulant use.

Oral anticoagulants

Apixaban, dabigatran, rivaroxaban and warfarin are oral anticoagulant medicines approved in New Zealand. These medicines are used in the prevention and/or treatment of blood clots.

Bleeding is a known side effect of oral anticoagulants, resulting from the action of these medicines on the coagulation cascade. Such risks are reflected in the data sheets and consumer medicine information.1-4

What is abnormal uterine bleeding?5

Abnormal uterine bleeding (AUB) is defined as a variation from the normal menstrual cycle. This may include changes in regularity, frequency, duration and volume of flow.

AUB can be caused by structural uterine pathology (such as fibroids or cancer) or nonuterine causes (such as polycystic ovary syndrome or medicines that interfere with blood clotting, such as anticoagulants).

Heavy or prolonged uterine bleeding can interfere with daily activities, and in some cases, may lead to iron deficiency with or without anaemia.

Some individuals may be at a higher risk of AUB when taking anticoagulants6,7

The risk of AUB occurring with oral anticoagulant use is higher in pre-menopausal individuals and individuals with a history of AUB.

Limited data from randomised clinical trials and observational studies suggests that the uterine bleeding profile may differ across oral anticoagulants.

The risk of AUB may be higher with rivaroxaban compared to apixaban and warfarin. There is limited information for dabigatran.

Evaluate for AUB during oral anticoagulant therapy6,7

When starting oral anticoagulant therapy, ask patients about their current and past menstrual bleeding patterns.

Inform pre-menopausal patients that they may experience new or worsened AUB and post-menopausal patients that unexpected uterine bleeding may occur with oral anticoagulant use. Remind patients to seek medical attention if they experience these symptoms.

AUB may develop at any time during therapy. Ask about changes to uterine bleeding patterns during follow-up appointments.

If AUB occurs while on anticoagulant therapy, consider possible underlying causes (such as fibroids, endometriosis or cancer).

New Zealand case reports

During the Monitoring Communication period, the Centre for Adverse Reactions Monitoring received four reports of AUB associated with rivaroxaban. No reports were received for apixaban, dabigatran or warfarin.

Table 1 outlines the number of reports of AUB with oral anticoagulants up to 27 September 2023, including those received with the Monitoring Communication.

Table 1: Number of reports of abnormal uterine bleeding, by reported term, with oral anticoagulants reported in New Zealand, up to 27 September 2023

Reported term Oral anticoagulant
Apixaban Dabigatran Rivaroxaban Warfarin
Intermenstrual bleeding (bleeding between periods) 0 0 0 1
(heavy bleeding)
0 0 3 2
(bleeding at irregular intervals)
0 0 1 0
Vaginal haemorrhage 0 3 2 1
Uterine haemorrhage 0 0 1 0
Total 0 3 7 4

Source: Centre for Adverse Reactions Monitoring, data extracted 27 September 2023

More information


  1. Pfizer New Zealand Limited. 2019. Eliquis New Zealand Data Sheet 30 August 2019. URL: (accessed 30 October 2023).
  2. Boehringer Ingelheim (N.Z.) Limited. 2020. Pradaxa New Zealand Data Sheet 11 March 2020. URL: (accessed 30 October 2023).
  3. Bayer New Zealand Limited. 2023. Xarelto New Zealand Data Sheet 29 May 2023. URL: (accessed 30 October 2023).
  4. GlaxoSmithKline NZ Limited. 2023. Marevan New Zealand Data Sheet 14 March 2023. URL: (accessed 30 October 2023).
  5. Kaunitz A. 2023. Abnormal uterine bleeding in nonpregnant reproductive-age patients: Terminology, evaluation and approach to diagnosis. In: UpToDate 24 July 2023. URL: (accessed 19 October 2023).
  6. Godin R, Marcoux V and Tagalakis V. 2017. Abnormal uterine bleeding in women receiving direct oral anticoagulants for the treatment of venous thromboembolism. Vascular Pharmacology 93–5: 1-5. DOI: 10.1016/j.vph.2017.05.001 (accessed 27 June 2023).
  7. Samuelson Bannow B. 2020. Management of heavy menstrual bleeding on anticoagulation. Hematology: American Society of Hematology. Education Program 2020(1): 533-7. DOI: 10.1182/hematology.2020000138 (accessed 27 June 2023).
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