Menstrual Cycles 101 – Part 4: Why am I spotting?

Happy #MenstrualMonday! By now, you’ve probably read the first 3 installations of the Menstrual Cycles 101 series. We’ve talked about what normal, heavy, and non-existent periods are like. Now it’s time to talk about spotting in between periods, which is a super common, and let’s face it messy, unpredictable nuisance to many women. 

The most common causes of spotting in between periods are:

  • Polyps
  • Fibroids
  • Vaginal Infections
  • Medications



There are two types of polyps that can cause spotting in between periods – uterine polyps and cervical polyps. Uterine polyps are growths found inside of and on the lining of the uterus, that can cause spotting. Uterine polyps can also cause heavy periods. Cervical polyps are found on the cervix. The cervix is the bottom part of the uterus. Polyps can form on the cervix which can cause spotting in between periods, or even bleeding after sex.


As mentioned in Part 2 of this Menstrual Cycle series, fibroids are growths in the uterus that can cause heavy bleeding. Sometimes these growths can even be culprits for spotting in between periods as well.

Vaginal Infections

There are many different types of infections that can cause spotting. Some of the most worrisome infections, like Sexually Transmitted Infections (STIs), can cause spotting in between periods. An STI that commonly causes this symptom is chlamydia. Also, women who have really severe yeast infections can have spotting. You will be able to read more about these vaginal infections in future posts.


The most common medications that can cause spotting is birth control pills. These pills affect the hormones involved in the ovulatory menstrual cycle, as mentioned in Part 1 of this series. Due to the effects of birth control pills, it can cause changes to the lining of your uterus that can cause spotting in between periods. Other medications, like blood thinners can also cause spotting in between periods.

So how do you know what is causing your annoying spotting? You’ve probably guessed what I’m going to tell you… see your doctor! Your doctor will carefully evaluate your symptoms and examine you. They may perform an ultrasound and order  blood work so they can get to the bottom of it how best to fix it.