What Causes Bleeding Between Periods?

by Robin Elise Weiss, Ph.D. Health Professional

Your period is not expected for weeks, but you find that you are spotting or bleeding. What could this mean? It's normal to worry, but before you panic, you should know that there can be many reasons for bleeding in between periods. Some of the causes of this sort of bleeding are harmless, but some of them are quite serious. Technically, bleeding between periods is not considered normal, and you need to figure out the source.

What is considered abnormal uterine bleeding?

Breakthrough bleeding, also called intermenstrual bleeding, is bleeding that occurs in between two periods and is one form of what is defined as abnormal uterine bleeding. Other forms of abnormal bleeding can include:

What causes bleeding between periods?

A number of things can cause bleeding between periods. The majority of the causes are easily identifiable and treated, while others may take some time to track down or may be more problematic.

Often, your hormone levels are what lead to abnormal bleeding. Hormonal abnormalities can be caused by a number of factors, including illness or medication, including birth control.


Any illness that creates havoc on your endocrine (hormonal) system can interfere with your menstrual cycles. This means that if an illness, such as problems with your thyroid, alters your estrogen or progesterone, you can easily have breakthrough bleeding. These issues are often easily identified by seeing your doctor or midwife. Sometimes they can figure out the problem just from taking a health history, but blood work can also confirm or identify the cause.

Birth control

Birth control methods of nearly all types can cause fluctuations in your cycles. This is particularly true if you are starting a new method of birth control. So if you are starting a new method, or even just a new brand, talk to your provider about when bleeding between your cycles might be normal, and when you need to seek help for it.


As you age, your body begins to head into perimenopause. You still have periods during this time, but they can become irregular, sometimes leading to bleeding between periods. Your doctor or nurse practitioner can help diagnose perimenopause.

Structural abnormalities

You may also find that you have an issue with your uterus on a structural levelthat is causing bleeding between periods. An example might be a fibroid, or a polyp. These can be identified with the use of physical exams and ultrasound. But you may also need additional testing, including an endometrial biopsy.


Many people worry about cancers like uterine cancer or cervical cancer as a reason for bleeding between periods, but this is the case only around two percent of the time. Still, even with those low numbers, it is important to get abnormal bleeding checked out sooner rather than later.

Treatment for bleeding between periods

The treatment for bleeding between periods will depend on the cause. For example, if bleeding is related to a new birth control method, sometimes time (and patience) will help. If bleeding is related to another disease, like thyroid disease, there may be specific medications you can take to address the issue. Or you may require surgery to help in the event of a structural issue or cancer.

Some of the surgeries can be simple, like a dilation and curettage (D&C) or an endometrial ablation. Other surgeries may remove part or all of the structure in question, or lead to a hysterectomy.

In the end, it’s important to realize that there is no substitute for working with your doctor when you’re dealing with abnormal bleeding. They can help you figure out the cause and help you design a treatment plan to get you back on the road to a normal menstrual cycle.

Robin Elise Weiss, Ph.D.
Meet Our Writer
Robin Elise Weiss, Ph.D.

Robin Elise Weiss, Ph.D., LCCE, CLC, AdvCD(DONA) is a childbirth educator, doula, founder of Childbirth.org, and the award-winning pregnancy and parenting author of “The Complete Illustrated Guide to Pregnancy” and more than 10 other books. Between her nine children, teaching childbirth classes, and attending births for more than two decades, she has built up an impressive and practical knowledge base. You can follow Robin on Twitter @RobinPregnancy, Instagram @Robineliseweiss, and Facebook @childbirthtrainings.