Every month (or so) millions of women from puberty up until menopause experience their menstrual cycle. Just like each woman is different and unique, so is their period. Some last for a few days, while others span over a week. Some periods cause shooting pain into the abdomen, coupled with cramps, while others stroll blissfully through their cycle without so much as a bloated belly. But more noticeably, some women have light, medium, or heavy bleeding each month — what does it mean?

For starters, the blood is a result of a clockwork system. Every month, the woman’s body prepares itself for pregnancy by creating a thick lining inside the uterus. If no pregnancy occurs, menstrual blood leaves the uterus and releases from the body through the vagina. Menstrual blood is a blend of blood, tissue from the uterine lining, and remnants of the eggs that weren’t fertilized that month. Learn about what happens when you have a heavier flow than your friends or family; you may be surprised by what it means for your health.

1. You don’t have fewer eggs than the average person.

A woman will experience 500 menstrual cycles during her lifetime, between 21 to 35 days, and which last between 2 and 6 days long. Hormones play a huge part in that. By the time a woman hits puberty she has about 300,000 eggs and loses about 1,000 each month regardless of how much blood is lost during that cycle. So don’t worry, you probably aren’t going to have any fewer eggs than your lucky friend with the light period.

To find out what your menstrual cycle can tell you about your fertility, read here.

2. It may be a simple, fairly treatable hormone imbalance.

The hormone estrogen builds up the lining of the uterus. The hormone progesterone is responsible for stabilizing the lining. When progesterone decreases it signals the uterus to shed the lining, which starts our cycle. However, if progesterone levels don’t drop as they should, the lining will continue to build up until it becomes too thick and unstable, which leads to a heavy bleeding.

Changes in hormone levels, the approach of menopause, and certain birth control pills can trigger abnormal bleeding. Just a slight tilt in the balancing act between estrogen and progesterone can throw your cycle off, which is why there’s no need to panic. Just get it checked out by a doctor and be sure to go prepared with a list of menstrual cycle dates you tracked.

3. You’re not losing as much blood as you think.

While it is not uncommon to soak through a pad or tampon, some bleeding can be abnormally heavy or long-lasting. In most cases, you just need to keep track of the days your period is usually the heaviest and use it as a predictor of when to switch to a more absorbent or super pad or tampon.

The average woman loses around 2 to 3 tablespoons during the entire period cycle. For those with heavier periods, women experience soaked-through tampons or pads every few hours or so, forcing them to wake up in the middle of the night to change their sanitary napkins. It’s only worrisome if this occurs for more than seven days; in that case, you should visit to your doctor or Ob/Gyn.

4. Untreated heavy bleeding can lead to anemia.

Menstrual bleeding that’s heavy and lasts more than seven days should be checked out by a doctor because it can lead to an iron deficiency known as anemia. Even mild anemia can cause weakness and fatigue, and in serious cases shortness of breath, rapid heart rate, lightheadedness, and headaches. Iron supplements should help bring oxygen levels in the blood levels to normal.

According to the Centers for Disease Control and Prevention, anemia symptoms or heavy bleeding can be signs of menorrhagia. Menorrhagia, which is an abnormally heavy menstrual cycle, is typically caused by a hormonal imbalance in the body. Those who are at the greatest risk for menorrhagia are adolescent girls who recently started their menstrual cycles and women approaching menopause.