What causes spotting? The lowdown on bleeding between periods

Seeing blood in your underwear when you’re not due for your period can be unsettling, but it’s actually more common than you might think.

Around a third of women will experience what’s known as abnormal uterine bleeding, which includes light bleeding or spotting outside of the normal period that may not be heavy enough to need a tampon or pad. There are many possible causes.

So what is spotting? And when should you speak to your doctor about it? We asked an obstetrician and gynecologist (OB-GYN).

Remember: You know your body best, so it’s always worth getting any vaginal bleeding checked out if you have any concerns. 

Key takeaways

• Spotting simply describes bleeding between your periods. Typically, spotting is lighter than your normal period. 
• Between fluctuations in your hormones to birth control and having sex, there can be lots of reasons why you might experience spotting, and usually, it’s nothing to worry about. 
• If you notice any changes in your cycle, then it can be a good idea to keep your health care provider in the loop. They can run some tests if necessary.

What is spotting? 

Before we get into what can cause spotting, it can be helpful to understand what it is. Experts define spotting as blood or bloody vaginal discharge that isn’t heavy enough to require a pad or tampon. 

This can be confusing as spotting might look like small dots of darker blood in your underwear. However, if it mixes with your discharge, it can look slightly different. Healthy vaginal discharge tends to be clear or white. But if you’re spotting, the blood can mix in and make your discharge appear pink. A darker color means the blood is older because it’s had contact with the air and “oxidized.” Fresh blood is a brighter red.

While spotting may not be as heavy as your period typically is, you may still choose to wear a pad or panty liner to stop the blood or discharge from staining your underwear. 

The differences between spotting and your period

If both spotting and your period include blood, how can you tell the difference? Well, the truth is it may be difficult. 

Dr. Jennifer Boyle, an OB-GYN at Massachusetts General Hospital, US, says: “Not all vaginal bleeding represents a menstrual period.” She explains that there are a few key differences between your period and spotting to look out for: 

• Spotting can happen at random points in your cycle, whereas if you have a regular cycle, your period can be tracked. Due to fluctuations in your hormones, your period happens when the lining of your uterus builds up and then breaks down. You can work out when your period might be using a period calculator or a period-tracking app like Flo. Spotting can also be caused by changes in your hormones but can happen at any point in your cycle.
• Spotting is a lot lighter than your period. 
• Spotting may appear like pink or brown discharge rather than bright or dark red blood. 

Light bleeding before your period

You might notice light bleeding just before your period begins. If this isn’t typical for you, try not to panic. “It is very normal for a menstrual period to start very light before it turns into normal flow,” says Dr. Boyle. “Some people have spotting for one to two days before heavier bleeding begins. It’s also normal to have one to two days of spotting at the end of a period too.”

Things that might cause spotting

Bleeding outside of your period can be confusing, but logging spotting in Flo can help you and your doctor see any patterns in your cycle (e.g., light bleeding just before your period). You can then have this information available in the app if you want to share it with your doctor. 

There are some common reasons for spotting that they might want to rule out before running any tests: 

Ovulation 

Ovulation is when one of your ovaries releases an egg in the hope of being fertilized by a sperm (aka you becoming pregnant). This typically happens at around the midpoint in your cycle if you have an average cycle length of around 28 days.  

Your estrogen levels rise just before ovulation during your fertile window. This is the few days in your cycle when you’re most likely to get pregnant. Estrogen plays a key role in triggering the lining of your uterus to thicken in preparation for a possible pregnancy. But if you don’t conceive, your estrogen levels start to drop again. 

This shift can cause a little light bleeding (or pink or brown discharge). Ovulation spotting is relatively rare, though. Research suggests that less than 5% of us experience it. 

Implantation bleeding

After your ovaries release an egg during ovulation, it may be fertilized by a sperm and start the journey down one of your uterine tubes to attach to the lining of your uterus. This is called implantation and officially marks the beginning of pregnancy. 

While there isn’t a lot of medical proof, some people say that they experienced spotting and cramping around the time that they think implantation happened. However, everyone is different, so you may not experience this. 

Pregnancy

Bleeding during pregnancy may sound like a red flag. However, you might experience light spotting during early pregnancy as your hormones go through some pretty monumental changes. 

It’s always worth speaking to your health care provider if you are experiencing bleeding during pregnancy. It could be a sign of an infection or pregnancy complication, so your doctor may want to check you and your baby over. 

Perimenopause

Another time when you go through big hormonal changes is perimenopause. Perimenopause describes the four- to eight-year transition to menopause. During this time, the amount of estrogen produced by your ovaries begins to fluctuate, which can trigger spotting. 

You might also experience longer or shorter cycles than you’re used to. Perimenopause usually starts in your mid-40s, but it can happen earlier. Chat with your doctor about any changes you’re experiencing. 

Hormone-based birth control

If you start taking hormonal birth control, such as pills, patches, injections, or intrauterine devices, it can take your body some time to readjust to the hormone levels. This can lead to spotting. Usually, this happens within the first three months of starting a new hormone-based birth control method. Health care professionals call this “breakthrough bleeding.” 

Dr. Boyle explains that “withdrawal bleeding” is also typical when you take hormonal birth control. While some hormonal birth control methods can be used continuously, others have a seven-day placebo period or break. During these few days, you might have a bleed that looks and feels like a period. However, it’s actually withdrawal bleeding. 

“Many people who use hormonal birth control will experience their withdrawal bleeding episodes as very light. This is one of the many benefits of these methods, in addition to preventing pregnancy,” says Dr. Boyle. “Sometimes, the withdrawal bleeding will just be spotting. This is completely OK and normal.” 

Having sex with your partner

Spotting after sex can be quite scary, but try not to be alarmed. It can happen for a few different reasons, including: 

Friction: Sex can cause friction or tears in your vagina. This might sound dramatic, but they aren’t uncommon after sex, especially if you experience vaginal dryness. There’s absolutely no shame in reaching for the lube before penetrative sex with a partner. You can explore the best type of lube for you together. 

Irritation of the cervix: Your cervix is the small muscular tube that connects your vagina to your uterus. If you have polyps — small, noncancerous growths — on your cervix, then this could lead to light bleeding after sex. If you have questions or concerns, don’t hesitate to speak to your health care provider. 

Some sexually transmitted infections (STIs) 

If spotting appears alongside other symptoms, it may indicate that you have an STI, like gonorrhea or chlamydia. Other symptoms to look out for include: 

• A change in the way your discharge looks and smells 
• A fever
• Pain when you pee
• Pain during sex
• Itching around your vulva 

The thought of having STI testing might sound daunting, but it’s crucial that you get the health care you need. If left unchecked, STIs can get worse, and your symptoms may become more severe as time goes on. You may develop other conditions, such as pelvic inflammatory disease, or develop complications if you try to get pregnant in the future. Tests are quick, and your doctor will be able to explain your best next step. Often, STIs are easily treated.

Uterine fibroids or polyps

Uterine fibroids and polyps are two types of noncancerous growths. Generally speaking, polyps can grow in your uterine lining, while fibroids can grow in your uterine muscle. They can cause irregular bleeding between your periods, often resulting in spotting. 

Reading the term “growth” might be scary, but often, polyps and fibroids don’t have any symptoms. In fact, you may not even know you have them. If you have noticed a change in your cycle, including new spotting, speak to your health care provider. They may suggest an ultrasound scan if they suspect you have polyps or fibroids. 

When to see your doctor and what to say

As a general rule, if you ever notice any changes in your cycle — be that spotting or longer, shorter, or more painful periods — then you should book a checkup with your doctor to figure out what’s causing your symptoms and get advice on the most appropriate treatment options or next steps. However, you should reach out to your health care provider immediately if you notice: 

• Persistent spotting or bleeding after sex
• Frequent spotting or bleeding in between periods or spotting that is not part of your period
• Spotting that doesn’t turn into a normal period (unless it is just light withdrawal bleeding from the birth control you’re taking)
• Green, yellow, thick, or clumpy vaginal discharge
• A strong vaginal odor or change in the way your vulva smells 
• Redness, itching, burning, or irritation around or inside your vulva
• Blisters or sores on your vulva
• Swelling of your vulva 
• Pain when you pee
• Pain in your lower abdomen or pelvic area
• A fever higher than 100.4 F (38 C)

Dr. Boyle explains that there are some questions your doctor might ask you at your appointment. If you’d like to prepare beforehand, think about: 

• When did the spotting begin?
• Can you give exact dates of when you saw the spotting and dates of any regular periods?
• Are you noticing any other changes in your vaginal discharge? 
• Does spotting happen after sex?
• Have you had any new sexual partners?
• What kind of birth control are you using?
• Is there any way you could be pregnant?
• When was your last Pap smear, and have you ever had an abnormal Pap smear result?