Menstrual Flow: How Much Blood Do You Lose During Your Period, and How to Manage It

"Am I bleeding too much?" It's one of the most common questions about periods, and a fair one: you rarely see how much blood you actually lose, and your flow can look alarming. In this article, we go over the numbers, what counts as a heavy flow, the signs that mean you should see a doctor, and ways to make your period easier to live with.

How much blood do you lose during your period?

According to Women's Health Concern, the patient information arm of the British Menopause Society, the average amount of blood lost during a period is about 35 ml, roughly 2 to 3 tablespoons over the whole period.

Yet the flow often seems like more. That's normal: menstrual flow isn't only blood. It also contains tissue from the uterine lining, cervical mucus and vaginal secretions. In total, you lose on average 70 to 80 ml of fluid per cycle, about half of which is blood.

A few more benchmarks:

• Periods usually last 3 to 7 days.
• About 80% of the flow happens in the first 3 days. That's why the start of your period often needs more protection.
• Everyone is different, and your flow can vary from one cycle to the next, with age, stress or a change in contraception.

Light, normal or heavy flow: how can you tell?

Medically, heavy menstrual bleeding has traditionally been defined as losing more than 80 ml of blood per cycle. But nobody measures their flow down to the millilitre. In practice, doctors focus mostly on how your period affects your daily life.

To get an idea, look at how often you need to change your protection. A fully soaked regular tampon holds about 7 ml of fluid. If you need to change a regular product more than once every 2 hours, or if your flow soaks through your clothes, your flow is probably heavy.

Signs that you should see a doctor

The American College of Obstetricians and Gynecologists (ACOG) lists these signs of heavy menstrual bleeding:

• bleeding that lasts more than 7 days;
• bleeding that soaks through one or more pads or tampons every hour for several hours in a row;
• needing to wear more than one pad at a time;
• needing to get up during the night to change your protection;
• blood clots the size of a quarter or larger.

Also see a health professional if you notice:

• bleeding between periods or after sex;
• bleeding after menopause;
• unusual tiredness, dizziness or shortness of breath. Repeated heavy periods can lead to iron-deficiency anemia;
• a sudden, lasting change in your usual flow.

In most provinces, you can call 811 to speak with a nurse (Info-Santé in Quebec), or book an appointment with your family doctor or a clinic. Heavy periods are common and very treatable: never hesitate to talk about it.

What can cause a heavy flow?

A heavy flow isn't always a sign of a problem. But when it's unusual or very heavy, a doctor may look into several possible causes, including:

• hormonal imbalances, which are common in the teen years and approaching menopause;
• uterine fibroids or polyps;
• adenomyosis;
• bleeding disorders, such as von Willebrand disease;
• certain medications, or a copper IUD.

Only a health professional can make a diagnosis and suggest the right treatment for you.

How to manage a heavy flow day to day

1. Choose protection designed for your flow

Protection that's too light opens the door to leaks and stress. Heavy-flow period underwear offers a large absorbent area and a leak-proof barrier, with nothing to insert. Our Libre by Deys styles are designed precisely for heavy flow, with up to 12 hours of protection.

2. Match your protection to the time of day

• During the day: invisible period underwear stays discreet under fitted clothes.
• At night: when you're lying down, flow can run toward the back. A full-coverage cut like our period boxer protects better.
• Days 1 to 3: plan to change more often, and keep a spare pair in your bag with a waterproof pouch.

3. Track your cycle

Note in a calendar or an app when your period starts, how long it lasts and how many times a day you change your protection. This helps you plan ahead, and it's very useful information if you see a doctor.

4. Look after your iron levels

Heavy periods cause iron loss. A diet that includes iron-rich foods (red meat, poultry, fish, legumes, tofu, leafy greens), paired with foods rich in vitamin C to help absorption, helps maintain good iron stores. Don't take iron supplements without talking to a health professional first.

5. Listen to your body

Fatigue, cramps, needing rest: heavy-flow days sometimes call for slowing down. Stay well hydrated, and don't hesitate to see a doctor if pain or bleeding stops you from living normally.

Frequently asked questions

Is it normal to have clots?

Small clots, especially on heavy-flow days, are common. Clots the size of a quarter or larger, especially if they happen regularly, are worth getting checked.

Can my flow change with age?

Yes. Periods are often irregular and sometimes heavy in the first years after your first period, and again as you approach menopause (perimenopause). A marked change is still worth mentioning to your doctor.

Can period underwear handle a heavy flow?

Yes, if it's designed for heavy flow and changed on time. It's all explained in our guide How does period underwear work? If you regularly go through any product's capacity in less than two hours, that's a sign to show a doctor.

In summary

On average, you lose about 35 ml of blood per cycle, mixed with other fluids, mostly in the first 3 days. Above 80 ml of blood, or if your period disrupts your daily life, it's considered a heavy flow, and it's worth seeing a doctor. Day to day, the right protection, tracking your cycle and paying attention to your energy levels make all the difference.

Discover our heavy-flow period underwear, proudly designed in Quebec, and learn how to care for it properly.

Sources

• Women's Health Concern, Heavy periods (fact sheet, 2026)
• American College of Obstetricians and Gynecologists, Heavy Menstrual Bleeding
• Menstrual Matters, Menstrual blood loss: what's normal?
• CDC, About Heavy Menstrual Bleeding

This article is for information only and does not replace advice from a health professional. If you have concerns about your cycle, see your doctor or call 811, the health line available in most provinces (Info-Santé in Quebec).