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Depending on how much blood you lose on your period, it can sometimes feel like you’re living through Shark Week. But just how much blood is supposed to be flowing?

It actually depends on the natural rhythm of your individual flow and whether you have any medical conditions that might cause more or less blood loss.

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The average amount of blood lost during your period is actually only 30 to 72 milliliters (about 2 to 5 tablespoons). Some research also suggests the average is closer to 60 milliliters (or 4 tablespoons). Either way, it’s definitely a lot less than it feels like.

But these are only averages, and your average blood loss during menstruation may be different.

Then what’s considered a light blood loss during your period?

If you find that your menstrual blood loss regularly falls in the “less than 30 milliliters” category, you’re the proud owner of a light period. But if you experience a light period when that isn’t your norm, it may be a sign of an underlying issue.

And what’s considered heavy blood loss during your period?

Some experts say a heavy period can be around 80 milliliters (about 5.5 tablespoons) or more.

Having a heavy flow isn’t something to be worried about. Heavy bleeding (aka menorrhagia) is normal for many folks, and treatment isn’t always needed. But if your bleeding starts to interfere with your daily life or if other symptoms pop up, it’s best to talk to your doctor.

At a glance: Period blood loss is a range

Light = less than 30 milliliters per month

Normal = 30 to 60 milliliters per month

Heavy = 80+ milliliters per month

No matter how much you lose, just remember: There’s no right or wrong answer for how your period is supposed to be. Your normal is unique to you, and knowing your cycle can help you determine if things are business as usual or if there’s a glitch in the matrix.

Before you bust out your calculator, it’s important to understand that your flow isn’t just blood.

What comes out during your period is a lovely mixture of blood and a slew of other materials, like mucus and uterine tissues. In fact, one study back in 1985 found that only 36 percent of menstrual flow is blood.

While it’s not an exact science, it’s still possible to get a good estimate of your total blood loss based on your preferred period product

If you use menstrual cups or discs…

Because they collect the fluid rather than absorb it, menstrual cups or discs will make measuring your blood loss way easier.

Cups typically hold 30 to 60 milliliters at a time, and some even have volume markings to help you track your flow. If your cup is unmarked, just check the packaging or the manufacturer’s website to find out the capacity.

Discs don’t have markings, so you’ll want to check the packaging or the web to see how much they hold.

During your period, keep a record of how much fluid is in your cup or disc every time you take it out. Do this for your next three or four cycles. (Because there truly is an app for everything, you can also log this in a handy-dandy period tracking app.)

If you use tampons, pads, or period undies…

Because they absorb the fluids, tampons, pads, and period underwear make measuring more of a challenge.

You’ll first need to determine the item’s fully soaked capacity. This info will be on your preferred product’s packaging (or you can always check online!).

To estimate how much you’re losing, keep a record during your period of the following:

  • what product you’re using and what size it is
  • how full it is when you change it
  • how often you change it

Track this info for your next three or four periods so you have enough info to determine your average total loss.

Don’t let your cup (or pad or tampon) runneth over

When using any absorbent product, you want to avoid letting it get fully soaked. Maxing out a product’s capacity can cause leaks and lead to a bunch of unpleasant side effects. Follow the golden rule of changing your period product every 4 hours.

After a few cycles, you should have enough info to determine your average total loss based on your period product of choice. Using this number, you can figure out how much is actually blood versus all the other things that come out.

To figure out if your total blood loss is in the “normal” range of 30 to 60 milliliters, multiply your total loss by 0.36.

Then, to get an idea of how much of your flow consists of other elements, subtract the resulting number from your total loss.

The period math word problem you never asked for

Question: Say you collect 150 milliliters of period fluid. How much period fluid is blood, and how much is the other stuff? Is the total blood loss amount considered “normal”?

Answer: Multiply 150 by 0.36 to get a total blood loss of 54 milliliters. This is in the “normal” range. Then subtract 54 milliliters from 150 milliliters to find that your period contained 96 milliliters of other components like uterine tissues and mucus.

So you’ve done the math and found you have a consistently heavy period (more than 80 milliliters per month). While it may just be how your body rolls (or flows!), it can also be a sign of an underlying condition or the effect of a medication. Here’s what could be to blame.

Intrauterine device (IUD)

An IUD is a contraceptive device that’s implanted in your uterus. During the first few days after it’s inserted, you might have cramping, back pain, and heavy bleeding. You may also experience longer, heavier, and overall irregular periods for the first 6 months.

Polycystic ovary syndrome (PCOS)

PCOS is a hormonal condition that impacts the way your ovaries work. It can cause irregular periods, weight gain, and hair growth in unwanted places (like your face, arms, back, chest, and abdomen).

Endometriosis

Endometriosis is a condition where the tissue that should be growing inside your uterus grows outside it instead. Endometriosis can cause pelvic pain, pain during sex, and bleeding between periods.

Pelvic inflammatory disease (PID)

PID is the p-i-t-s. This infection in your uterus, ovaries, or fallopian tubes can cause painful urination, severe abdominal pain, and irregular bleeding (both during and between periods).

Fibroids

Fibroids are noncancerous tumors that form in the muscles of your uterus. They can cause lower back pain, abdominal pain, and constipation, among other symptoms.

Polyps

No, polyps are not something you’d find in a garden. These noncancerous growths can develop in the lining of your uterus or cervix, preventing your uterine muscles from contracting.

This, in turn, prevents the lining of your uterus from shedding the way it’s supposed to, which can cause irregular periods, longer or shorter periods, or even bleeding between periods.

Adenomyosis

It may sound like something straight outta “Mary Poppins,” but adenomyosis is actually a condition where your uterine tissue embeds itself into your uterine walls instead of shedding and (literally) going with the flow. This can cause pelvic pain, pain during sex, large blood clots, and heavy, prolonged periods.

Hypothyroidism

Your thyroid produces hormones that regulate your body’s functions. An underactive thyroid doesn’t make enough hormones, throwing your body out of whack. This can cause weight gain, temperature sensitivity, and — oh, yeah — period problems.

Bleeding disorders

Some bleeding disorders can keep your blood from clotting, which can cause problems with your period and beyond. In addition to causing a heavy flow, these conditions can lead to unexplained nosebleeds, frequent bruising, and heavy bleeding after a cut or scrape.

Certain meds

Some medications (like anticoagulants and chemotherapy meds) can also prevent blood clotting, which can cause bleeding gums, easy bruising, heavy periods, and black or bloody bowel movements.

Think your flow is getting freaky when it comes to how much you bleed every month? Try these tips to help manage your irregular period probs.

Log it

Tracking your period can help you better understand your flow and determine what may or may not be normal for you. Keep track of when your period starts and stops, the number of times you change your period product, and any other symptoms you have.

Hydrate, hydrate, hydrate

Water is the elixir of life, and you should stay hydrated all the time. It’s especially key to keep up your H2O intake during your period, because your body is losing fluid. In addition to keeping you replenished, water can help ease PMS symptoms like dizziness and nausea.

Be Iron(wo)man

If your flow is heavy, your metal may not be (#DadJoke). A heavy flow can leave your body deficient in essential nutrients like iron. Low iron levels can make you feel tired and lethargic.

To boost your iron levels (and ease period symptoms!), enjoy iron-rich foods like:

  • meat
  • eggs
  • fish
  • nuts or seeds
  • tofu
  • whole grains

You know your body best. It’s normal for periods to change sometimes, but if something feels off, talk to your doctor.

Signs that warrant a trip to the doc:

  • bleeding for longer than 7 days
  • passing large blood clots (think bigger than a quarter)
  • your period restricting your daily activities
  • having to use double the period protection to prevent leaks, like a pad and a tampon
  • soaking through one or more pads, tampons, or cups every hour for several hours
  • experiencing signs of anemia, like fatigue and shortness of breath

If something foul’s afoot, your doctor can give you a diagnosis and work with you on a treatment plan.