Can menstrual cups really shorten your period?

Rhiannon’s periods were usually quite heavy and lasted about six days. The first few days were the heaviest, but even days 4-6 were a lot heavier than what she would consider to be normal. After going on the pill at age 16, Rhiannon used various contraceptives that sometimes made her period irregular and for a number of years, stopped it from coming.

In October 2017, she decided to come off contraception in order to try for a baby. She had been using a menstrual cup on-and-off since age 18, but this was the first stretch of time she would do so without being on any contraception. Her period came back and she started tracking it. She noticed that it was a lot shorter than it used to be.

“Now, sometimes my period is only for three full days and whilst still very painful the day before it starts and the first day, it eases a lot and becomes a lot lighter after the first day or two,” she says. “It could be the cup if other long-term users have found this, too. But it could be because of the various contraception I was on, and I’ve since been diagnosed with PCOS. So, I don’t know.”

Flow is purely a mechanical process — it’s gravity

Like other women who have noticed a shorter period since using a menstrual cup, Rhiannon isn’t certain that the cup is causing the changes to her flow. In fact, no one knows for sure, because there is no clinical research whatsoever on the topic.

Cherie Hoeger, CEO and co-founder of menstrual cup company Saalt, says that many of their users report a shorter cycle once switching to a cup. “We usually see a comment at least weekly in our Facebook group about this,” she says. “We hope more research is done in the future to better understand why this may be the case.”

Theory one: suction

One theory that has been floated is that because the cup creates suction once inserted, this can increase the flow and shorten the duration of the bleed. “I would find that difficult to believe, because the menstrual cup doesn’t form a complete seal with the vaginal walls,” says Professor of Gynaecology and Consultant Gynaecological Surgeon Dharani Hapangama, who also does research with women’s health charity Wellbeing of Women. “But, who knows, because no one has properly looked into this.”

While Obstetrician & Gynaecologist Dr Gemma Goodyear agrees that more research is needed to be sure, she thinks that this could be possible, due to the potential effect of the cup’s suction on the endometrial lining.

“I’ve not heard it personally, but it’s not a wild theory, because the cup has got some suction over the cervix so there is some suction on the last bits of lining towards the end of the cycle,” she says.

The endometrial lining doesn’t shed at a consistent rate, and in some it may shed more steadily and in others, shed more during the first few days of your period. So, if your endometrial lining has mostly been shed by, say, day three of your period, the suction created by the cup could theoretically help to pull it down faster, explains Dr Goodyear. “Flow is purely a mechanical process — it’s gravity,” she says.

Could this phenomenon be down to perception, because with a menstrual cup, we can see the amount of blood lost more clearly than with a pad or tampon?

Theory two: chemicals in menstrual products

Others suggest that the use of chemicals in pads and tampons may affect the vagina and, therefore, have an effect on the period. “It could be that the chemicals used, such as fragrances and dyes, irritate the vagina, causing cramping, and possibly affecting blood flow or clotting,” says Superintendent Pharmacist at The Independent Pharmacy Andy Boysan. “Menstrual cups are generally made from medical-grade silicone or latex, so wouldn’t have the same effect if this were the case.”

Again, there is minimal research into the effects of chemicals used in menstrual products on the period, and no industry-wide standards in the UK to ensure their safety. But, notes Dr Goodyear, the chemicals are unlikely to affect the flow itself, which refers to the process of the shed lining passing through the vagina.

Theory three: misperception

Could this phenomenon be down to perception, because with a menstrual cup, we can see the amount of blood lost more clearly than with a pad or tampon?

“I think that is very much more likely, and to some extent we have some evidence for that,” says Professor Hapangama. “There have been studies looking at women’s assessment of their amount of menstrual bleeding and the estimates are very wrong. That’s why for most clinical studies, [participant] estimates are not accepted. You need to collect the menstrual products worn by the participants and extract blood from those.”

It’s important, however, not to mistake these discrepancies in perception as an indication that women’s experiences are imagined or somehow less real

A 2004 review found that while someone’s estimate of their own menstrual blood loss is an appropriate reason to investigate further, it is not an accurate way to quantify blood loss. Across different studies, between 38-76% of women were found to accurately have identified that their flow qualified as heavy menstrual bleeding.¹

This is in part due to the thinking that if you use more menstrual products during a period, then your flow must be heavier. However, the most important reasons for changing menstrual products were found to be someone’s personal hygiene practices, how attentive they are to their flow, and their financial resources,² rather than necessarily changing them only once soaked through. Plus, different brands of pad and tampons vary in their absorbency.

And then there is the impact of personal bias towards cups, which may further skew perception of their effects. “Generally, using a menstrual cup requires more effort, so someone who has decided to use that is already biased towards it,” says Professor Hapangama. “From an academic perspective, we want to know things objectively. But if someone is already biased towards it, they will have a positive perception towards it. That’s why we do randomised controlled trials.”

It’s important, however, not to mistake these discrepancies in perception as an indication that women’s experiences are imagined or somehow less real. The disconnect between perceived and actual menstrual blood loss speaks more to a wider lack of education and understanding around menstrual health.

The reason why someone experiences a shorter period when using a cup could be down to any of the above factors, a combination of them, or none of them. Without dedicated clinical research, all we can do is hypothesise.

Featured image is an illustration of a woman sitting in her bathroom and holding an almost-full menstrual cup

Page last updated September 2020