Many women wonder how much blood is normal to lose during a menstrual period, and if this blood loss can pose any risk to their health. However, there is so much natural variation in cycle length, blood loss, and symptoms that it can be hard to determine what’s normal and what might be a cause for concern.
So how much blood loss is normal? And can this blood loss be related to conditions like anaemia?
But first, let’s recap what’s happening when your period comes. Every month, your body goes through a series of hormonal changes to prepare for a potential pregnancy. If this pregnancy doesn’t occur, the uterus sheds its inner lining during your menstrual phase, which is the blood (and tissue) that you lose during your period .
For most people, the amount of blood lost during a period isn’t enough to cause health problems. But in some cases, it’s possible for the blood loss to be significant enough to put you at risk for anaemia. Before diving into that, we’ll cover what anaemia is, its different causes, and how to spot the symptoms.
What is anaemia and what causes it?
At any given time, your heart is pumping about 4-6 litres of blood throughout your body. This blood has many important functions in your body: it carries nutrients and oxygen, fights infection, and regulates your body temperature .
Anaemia is a blood disorder where your body does not have enough red blood cells (RBCs). Red blood cells are the vehicle for haemoglobin in your body, a protein which carries oxygen. When this is low, your body receives insufficient oxygen, and you will likely feel fatigued or experience other symptoms .
There are many causes of anaemia. It can happen when your body doesn’t make enough RBCs, destroys them, or loses too many of them . Usually, if anaemia is related to menstruation, it falls into the category of losing too many RBCs . This happens when there is heavy blood loss during your period, which can cause low iron in the body, leading to an underproduction of RBCs (which need iron in order to make haemoglobin) . This is usually referred to as iron-deficiency anaemia, and it’s fairly common.
Heavy menstruation isn’t the only cause of anaemia, however. A lack of not only iron but also folate/folic acid and vitamin B12 can cause anaemia. This can be due to inadequate nutritional intake or can be related to other conditions such as Coeliac Disease, which can cause malabsorption of these nutrients . Furthermore, there are several medications, genetic, and non-genetic conditions which can impact the number, shape and function of the red blood cells, resulting in anaemia.
The symptoms of anaemia depend on the severity of the condition. If it’s very mild, you might not notice any symptoms at all, or you might notice tiredness, pale/yellowish skin, or general weakness. In more severe cases, however, symptoms include :
- Increased thirst
- Weak/rapid pulse
- Leg cramps during exercise
Heavy menstruation is a key cause of iron-deficiency anaemia in women, so it’s important to pay attention to its symptoms and get tested if you are experiencing fatigue, weakness, or other symptoms of anaemia .
But first, let’s explore the million-dollar question: How much blood loss is normal during a menstrual period? And, on the flip side, can anaemia actually cause you to lose your period altogether?
How much blood do you typically lose during your period?
Like with most things menstruation-related, there is a wide range of what’s considered normal. Some people have heavier flows, other people tend to have lighter ones. Typically, the normal range for the amount of blood lost during a period is around 2-3 tablespoons (or 10 to 35 ml), and the bleeding lasts about 4-5 days . Heavy menstrual bleeding—also referred to as Menorrhagia—on the other hand, is typically associated with symptoms like :
- Bleeding for more than seven days.
- Needing to change a normal-sized pad or tampon every hour for several hours and/or during the night.
- Passing clots that are larger than a quarter.
- Losing more than 80ml of blood (or 16 soaked pads) in a single cycle .
If you think you might be experiencing heavy menstrual bleeding, it’s a good idea to measure the amount of blood you’re losing during your period to see whether it falls in the normal range.
There are different ways to measure this. For example, you can count the number of normal-sized menstrual products you’re going through and how much time elapsed between them. Or you can use a menstrual cup that has millilitre readings on the side and count how much blood is lost in the course of one period.
Can anaemia cause you to lose your period?
While heavy menstrual bleeding can cause anaemia, on the flip side, there is some research to suggest that having iron-deficient anaemia can actually cause you to lose your period as well.
The research is still developing in this area, but there is some evidence that if iron-deficient anaemia becomes severe, your body will stop menstruating in order to avoid losing more iron (your body also may stop ovulating, a key part of your menstrual cycle, if iron is too low). However, the research done so far has been on mice, so it’s not yet clear whether it applies to humans. About 50 percent of women who have iron-deficient anaemia also experience amenorrhea (loss of period) , so while the connections aren’t entirely clear, iron certainly has an important role to play in overall fertility and menstruation.
What to do if you’re experiencing heavy bleeding or symptoms of anaemia
It’s a good idea to speak to your doctor if you have symptoms of heavy menstrual bleeding or anaemia to see what’s going on. They will perform a blood test to assess the complete blood count (CBC) or blood haemoglobin levels to determine if you have anaemia. Tests to measure for low iron, folate, vitamin B12 and inflammation are often added to help confirm the underlying cause of the anaemia.
The good news is that, in a lot of cases, the treatment is pretty simple: daily or intermittent iron supplementation is often enough to bring iron levels up to healthy levels . However, if there is an underlying cause of the heavy menstrual bleeding, that will be something your doctor will discuss with you further, as that may require intervention on its own.
Lastly, dietary changes can also help increase your iron levels. Incorporating foods like lentils, spinach, poultry, beef, nuts, and seeds into your diet will help support healthy iron levels .
Recap: Your period and anaemia
Anaemia is a condition with many causes and symptoms, so your period is just one factor. However, heavy menstrual bleeding is highly related to low iron levels in the body, so it’s important to pay attention to these symptoms, rather than dismiss them.
It’s common for menstrual symptoms like significant period pain or heavy bleeding to be normalised by those around us, but just because something is common doesn’t mean that it’s normal—it’s important to talk about any concerns you have with your doctor to rule out any underlying causes and make sure your iron levels aren’t too low.
Finally, if you are trying to conceive and know that you experience iron-deficient anaemia, it’s especially important to understand whether you are ovulating every month since iron has a role in ovulation and fertility .
The inne minilab uses your saliva to test progesterone levels—a key hormone in ovulation—from the comfort of your home.
Your daily readings are sent directly to your smartphone to help you understand whether you’re ovulating—and crucially, when you’re ovulating. These insights help to develop deeper self-knowledge and bodily awareness, which are important for overall health and well-being—whether or not you’re trying to conceive.
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