While alcohol can impact several hormones involved in menstruation, its exact effect on uterine bleeding isn’t clear.

Abnormal uterine bleeding (AUB) refers to heavy periods, or bleeding or spotting between periods. Many things can contribute to AUB, from medication side effects to endometriosis.

Alcohol may also contribute to AUB, but the exact link isn’t totally clear.

Here’s a closer look at the potential links between alcohol and uterine bleeding, what else might be causing your symptoms, and when to seek medical care.

The research around alcohol use and menstruation is both limited and conflicting.

An older research review from 2002 draws on research from the 1970s and ’80s that suggests a link between alcohol use and menstrual irregularities, even with low alcohol use.

However, a more recent study from 2014 reached a different conclusion. It involved interviewing 80,000 pregnant Danish women about their prepregnancy menstrual cycles and alcohol consumption.

Those who didn’t drink reported more menstrual irregularities than those who did. Keep in mind, the authors note this doesn’t mean drinking alcohol will reduce your risk of menstrual irregularities.

A 2015 cohort study reached similar conclusions. While moderate alcohol consumption resulted in increased levels of estrogen, testosterone, and luteinizing hormone, these increases didn’t have any short-term effects on menstrual cycle function, including uterine bleeding. There wasn’t a significant difference in menstrual function between binge drinking and non-binge drinking.

Based on the limited research available, it seems occasional drinking, even to a moderate degree, likely won’t cause AUB.

But more research is needed to understand the potential effects of heavy alcohol consumption or binge drinking on AUB.

Drinking alcohol may increase estrogen in your body. Estrogen stimulates the growth of the lining of your uterus. The more of this lining there is to shed at the start of the next menstrual cycle, the heavier the period.

The more alcohol you consume, the greater the increase in estrogen.

An occasional drink likely won’t affect your flow, but moderate to heavy drinking may have more impact.

Heavy alcohol consumption may cause symptoms that mimic those of menstrual cramps or AUB.

For example, heavy alcohol consumption can cause gastritis, or inflammation of the stomach. This can cause abdominal pain and bloating, both of which can be easily mistaken for period symptoms.

Long-term, heavy alcohol use can also lead to kidney damage. This can result in hematuria, or blood in the urine, which may resemble uterine bleeding.

Other causes of AUB

While alcohol may play a role in AUB for some people, many other things can cause it, too. These include:

  • Issues with ovulation: Lack of ovulation can cause a buildup of the endometrium, the tissue that lines the uterus and sheds each month during menstruation. This can result in heavy or irregular menstrual bleeding. Some possible causes of ovulation issues include:
  • Hormonal birth control: Hormonal methods of birth control can cause breakthrough bleeding, which is bleeding that occurs between periods.
  • Ovarian cysts: An ovarian cyst is a fluid-filled sac that develops on an ovary. Most ovarian cysts do not cause any problems and disappear on their own. However, a ruptured cyst can cause AUB.
  • Benign growths on the uterus: Fibroids and polyps are noncancerous growths that can form inside the uterus or on the cervix. Both can cause heavy or irregular menstrual bleeding.
  • Endometrial intraepithelial neoplasia (EIN): In EIN, the lining of the uterus grows too thick, which can result in AUB. Medical professionals refer to EIN as a precancerous condition because it can progress to endometrial cancer without treatment.
  • Endometrial cancer: More rarely, AUB may be an early symptom of endometrial cancer. Doctors usually detect the disease in its early stages, when treatment is most effective.

Consider talking with a healthcare professional about any changes to your menstrual cycle, including irregular bleeding, spotting between periods, or heavier periods. They can help determine the underlying cause and refer you to any necessary treatments.

If you experience an episode of very heavy uterine bleeding — either between cycles or during your usual one — seek immediate medical care.

If you notice uterine bleeding after drinking alcohol, it’s unlikely to be a direct result of drinking.

Most cases of AUB are due to other factors, such as hormone fluctuations, using hormonal birth control, or the presence of an underlying condition.

Still, alcohol may contribute to hormone fluctuations that increase estrogen and other hormones, which may impact your cycle.

If you experience AUB, talk with a healthcare professional to determine the cause. While some causes resolve on their own, others may require treatment.