It may not always be easy to tell the difference between spotting or a light period. If you’re experiencing unexpected vaginal bleeding, it’s a good idea to talk to a doctor. They can determine if the bleeding is normal or a sign of an underlying condition.

If you’re a woman in your reproductive years, you’ll typically bleed every month when you get your period. Sometimes you might notice spots of vaginal bleeding when you’re not on your period. Most of the time, this spotting is nothing to worry about. It can be triggered by a variety of factors, from pregnancy to a switch in birth control methods. It’s always a good idea to have your doctor check out any unexpected vaginal bleeding, especially if you’re not sure of the cause.

Here’s a guide to help you tell the difference between spotting and your period.

During your period, the flow of blood will usually be heavy enough that you’ll have to wear a sanitary pad or tampon to avoid staining your underwear and clothes. Spotting is much lighter than a period. Usually you won’t produce enough blood to soak through a panty liner. The color may be lighter than a period, too.

Another way to tell whether you’re spotting or starting your period is by looking at your other symptoms. Just before and during your period, you may have symptoms like:

If you have spotting that’s due to another condition, you may also have some of these symptoms, either at other times during the month, or at the same time you experience the spotting:

You get your period when your uterine lining sheds at the beginning of your monthly cycle. Spotting, on the other hand, may be caused by one of these factors:

  • Ovulation. During ovulation, which happens in the middle of your menstrual cycle, an egg is released from your fallopian tubes. Some women notice light spotting when they ovulate.
  • Pregnancy. About 20 percent of women have spotting during the first three months of their pregnancy. Often, the blood appears in the first few days of pregnancy, when the fertilized egg attaches to the uterine lining. Many women mistake this implantation bleeding for a period because it happens so early they don’t realize they’re pregnant.
  • Polycystic ovary syndrome (PCOS). Irregular bleeding is a symptom of PCOS, a condition in which your ovaries produce extra male hormones. PCOS is common in young women. It leads to the growth of small, fluid-filled sacs in your ovaries.
  • Birth control. Birth control pills can cause spotting, especially when you first start using them or you switch to a new one. Continuous birth control pills are more likely to cause breakthrough bleeding than 21- or 28-day pills. Spotting is also common in women who have an intrauterine device (IUD).
  • Uterine fibroids. Fibroids are small, noncancerous lumps that can form on the outside or inside of the uterus. They can cause abnormal vaginal bleeding, including spotting in between periods.
  • Infections. An infection in your vagina, cervix, or another part of your reproductive tract can sometimes make you spot. Bacteria, viruses, and yeast all cause infections. Pelvic inflammatory disease (PID) is a serious infection you can get from an STD like chlamydia or gonorrhea.
  • Cervical polyps. A polyp is a growth that forms on the cervix. It isn’t cancerous, but it can bleed. During pregnancy, polyps are more likely to bleed because of changing hormone levels.
  • Menopause. The transition to menopause can take several years. During this time, your periods will likely be more unpredictable than usual. This is due to fluctuating hormone levels. The bleeding should taper off once you’re in full menopause.
  • Rough sex or sexual assault. Any damage to the lining of the vagina can make you bleed a little bit.

You’re more likely to notice spotting in between periods if you:

  • are pregnant
  • recently switched birth control methods
  • just started to get your period
  • have an IUD
  • have an infection of the cervix, vagina, or other part of the reproductive tract
  • have PID, PCOS, or uterine fibroids

Although spotting is usually not a sign of something serious, it isn’t normal. Any time you notice bleeding outside of your period, you should mention it to your primary care doctor or OB-GYN. It’s especially important to call your doctor if you’re pregnant and notice spotting. Spotting could be a sign of a serious complication, such as an ectopic pregnancy or miscarriage.

During your visit your doctor will ask about your symptoms and do a physical exam to try to identify the cause of your spotting. The physical exam will likely include a pelvic exam. Tests that can help diagnose the cause include:

The treatment for spotting will depend on what condition is causing it. You might need:

  • an antibiotic or antifungal drug to treat an infection
  • birth control or other hormones to regulate your menstrual cycle
  • a procedure to remove polyps or other growths in your uterus or cervix

The outlook depends on the cause of your spotting. Spotting during pregnancy and from a birth control switch will usually stop after a few weeks or months. Spotting that’s due to an infection, polyps, fibroids, or PCOS should go away once the condition is under control with treatment.

Usually spotting is nothing serious, but it can be inconvenient, especially when you’re not prepared for the bleeding. One way to figure out whether you’re spotting or menstruating is to track your periods. Keep a diary or use a period app on your phone to record when your monthly bleeding starts and ends each month, and when you have spotting. Share it with your doctor to see if you can find any patterns.

Ask your doctor about hormone treatments that can help regulate your periods and prevent spotting. During pregnancy you can manage bleeding by getting as much rest as possible and by not lifting anything heavy.

Until you can get your spotting under control, always keep panty liners close by. Have a box at home and carry a few in your purse, just in case you start to bleed.