Period Flow: How heavy is too heavy?

It can be hard to figure out how much blood you’re losing during a period, especially if you’re using more than one product, leaking through them, and/or using different kinds of sizes for each day of flow. 

Many period products will say how much approximate fluid they can hold.

How much flow can a period product hold?

Commercial absorbent products (one-use pads and tampons) usually use these descriptors and parameters:

  • Junior: <6g (~1 tsp)
  • Regular: 6-9g (~ 1.5 – 2 tsp)
  • Super: 9-12g (~2 to 2.5 tsp)
  • Super plus: 12-15g (~3 tsp or 1 tbsp)
  • Ultra: 15 – 18g (>1 tbsp)

If you use a cup or a disc, there should be volume markings on there. Or, perhaps, the packaging will tell you how much it holds.

If you use period underwear or another product, those should tell you as well; however, period underwear claims tend to overestimate the quantity of blood they can hold. Depending on the feel and colour (which is usually dark), it can be really difficult to say how much blood you’re actually looking at.

How much flow is normal over a period?

On average, menstruators lose 30-50 mL of blood over 3-7 days.

Those are averages. Some people might naturally sit a bit beyond that.

Period flow contains lots of things like uterine tissue, cells from the vaginal wall, secretions from the vagina and cervix, and some of the bacteria that live in the reproductive tract.

Rarely, you may even shed a big membranous tissue called a decidual cast. This happens when the uterine lining is shed intact instead of in little bits.

How heavy is too heavy?

Heavy or prolonged menstrual bleeding can be called abnormal uterine bleeding.

This is when period flow volume goes >80 mL or >7 days of bleeding.  This should be discussed with your medical team to figure out what’s going on. Is it something like fibroids, adenomyosis, a clotting disorder, or endometriosis?

Other indicative signs could include anaemia, menstrual blood clots that are larger than 2.5 cm or 1″ in diameter, frequent period product change, doubling up on  products, and flooding beyond your products.

Scant bleeding, on the other hand, is defined as <10 mL of blood loss throughout your whole period.

Scant bleeding is usually seen in conditions where hormone production is low or suppressed, like if you’re using hormonal contraceptives, if you have primary ovarian insufficiency, or if you have hypothalamic amenorrhea.

Final thoughts

The odd time your menstrual flow changes is usually nothing to be concerned about. However, if you’re noticing persistent changes in your blood loss, I encourage you to make notes and consult with your medical team.

You could fall within normal limits, like 60 mL of flow, but if your previous normal was 20mL, that’s a three-fold difference! Sometimes people with changes that are significant but technically within range slip through the cracks.

It’s not that these changes are always sinister (in fact, these are examples of what we might see in the menopause transition or during puberty), but they should be checked out!