Period Leaks: How to Make Them Less Likely, and What to Do in the Moment

A leak is arithmetic, not a failure of character. The NHS says you lose about 20 to 90ml of blood over a whole period — roughly 1 to 5 tablespoons. A review of menstrual products in Obstetrics & Gynecology estimates that a fully saturated super pad holds about 5ml and a nighttime pad up to 15ml. Put those figures next to each other and the surprise is not that pads leak but that they hold as much as they do. A leak is a heavy hour meeting a product near the top of what it holds. The first half of this page is that arithmetic; the second half is what to do in the ten minutes afterwards, which almost nobody writes down.

This page is for anybody who has spent a lesson sitting very still, and anybody dreading doing so.

The numbers, side by side

Everything measured, on one scale, drawn against the largest figure on it.

Capacities as estimated by a 2023 review in Obstetrics & Gynecology; the underwear figure weighed in a randomised study of 20 adults. Total loss is the NHS's.

Look at the bottom bar against the top one. A whole period at the heavy end of the ordinary range is 90ml; the biggest capacity on that chart is 79ml, for a disc basin, and the smallest is a super pad's 5ml. That total is spread across several days, but not evenly, because a period has heavier stretches and lighter ones. The NHS puts that in terms of colour: at its heaviest the blood will be red, and on lighter days it may be pink or brown.

So a leak is one of those heavier stretches landing inside a lesson, a bus ride or a night, while the thing you are wearing reaches the top of its bar. Not a mistake you made. A capacity meeting a flow.

One more figure puts the page in proportion: across 213 normal cycles the median loss was 17ml — not an hour's worth, the cycle's. Which product suits which stretch of which day is answered in period products explained.

The trap in "just change it more often"

This is the one piece of advice that quietly stops working when the product changes, and a randomised study of 20 adults with heavy menstrual bleeding measured it over two cycles. Participants changed disposables a mean of 5.5 times a day, menstrual cups 3.3 times and period underwear 3.5 times — but the underwear held 22 plus or minus 18 grams of fluid against 48 plus or minus 30 grams with disposables. Fewer changes, less fluid held. The authors conclude that the frequency of changing or emptying underwear and cups is not equivalent to the frequency of changing pads or tampons, and that reusable products may therefore lead to missed diagnoses of heavy menstrual bleeding. They are careful about their own study too: the sample was sized for feasibility because no earlier work existed to power it, and eight of the ten cup users were new to cups.

That matters because the NHS's test for heavy periods is written in changes — needing to change your pad or tampon every 1 to 2 hours. If you are wearing something that is not a pad or a tampon, that clock reads reassuringly while you are still leaking. The capacity review makes the same point from the other end: no regulations exist regarding period underwear content or capacity. The full version is in period underwear, honestly.

Making leaks less likely

Nothing here is a rule or a moral position about products. It is what the capacities above imply.

• Match the product to the stretch, not to the day. The NHS notes that pads come in many sizes so you can choose one to suit how heavy or light your period is, and that pantyliners are a smaller, thinner type for very light days. The review puts a nighttime pad at up to 15ml and a super pad at 5ml, and nothing stops you wearing the bigger one at two in the afternoon.
• Two products at once is a real strategy and also a signal. Plenty of people double up for a long journey. Needing two types together is also on the NHS's list of signs of heavy periods — so if it is your default rather than your away-day plan, that is information.
• Change on a clock, not on a feeling. Before a long lesson, before the bus, before you leave the house. Waiting until you notice is waiting until it has happened.
• Carry the spare. Two products and a spare pair of pants in a pencil case is five minutes of preparation and removes most of the fear. The first period kit checklist is that list on one printable page, and periods at school covers who to ask when you have not got it.

It has already happened. Here is the next ten minutes.

This is the part left out of every leaflet, and the part you actually needed.

Cover it and buy yourself time. A jumper tied round your waist. A coat. A bag held at your side. None of it feels subtle to you and all of it is invisible to everyone else, and it turns an emergency into a walk to the toilets.

In the toilets, deal with the product first. Change it, then look at the clothes. Fixing the fabric while the cause is still running is how a five-minute problem becomes a twenty-minute one.

Cold water on the stain, never hot. Rinse from the back of the fabric if you can. If there is no time, blot it, put the spare pair on and deal with it at home — a stain rinsed cold and left is far easier later than one scrubbed hot now.

Ask. Out loud, in a normal voice. A teacher, the school nurse, the friend you would tell anything, your mum, your dad, an aunt, an older sister — whoever is easiest. Schools keep spares, and so do most people. The sentence is "I've come on and I've leaked, can I get sorted out", and adults hear it all the time.

At someone else's house, say so. The one that feels impossible and is the most straightforward: tell whoever lives there, and they will hand you something. If it is on a chair or a bed, say that too — cold water and a wash sorts it, and nobody sensible has ever thought less of anybody for it.

White trousers, on the bus, in front of everyone. Sit down. Tie something round your waist. Get off where you were getting off. A long ten minutes, and then it is over.

And the flat truth underneath all of it: other people notice enormously less than you think. Half of them have done exactly this, and the other half are not looking at you. You will remember it far longer than anybody else does, and it will not have changed a single thing about how anybody sees you. Being embarrassed is a normal reaction, and it is not evidence that anything shameful happened. Blood on a chair is a laundry problem.

When leaks stop being a laundry problem

Here is the turn, and it is not a scare. The NHS's list of signs of heavy periods includes, in its own words, bleeding through to your clothes or bedding — beside changing a pad or tampon every 1 to 2 hours, needing two types of product together, periods lasting more than 7 days, passing clots larger than about 2.5cm, avoiding daily activities, and feeling tired or short of breath a lot.

The NHS is equally plain that many women have heavy periods and they may be normal for you. So the point is not that a leak means something is wrong. It is that repeated leaks are information, and information is worth handing to a GP rather than hiding under a jumper for four years. Its threshold: see a GP if heavy periods are affecting your life, if you have had them for some time, if you have severe pain, or if you bleed between periods. What that appointment is like is in when to see a doctor about your period.

Why writing it down beats going on a feeling

There is a measured reason not to trust your own impression here. A clinical review of menstrual blood loss defines heavy menstrual bleeding as losing more than 80ml in a cycle, puts its estimated prevalence at 18 to 32%, and says it is known to be under-reported because people recognise and estimate their own loss poorly. The figure that proves it: 37% of women whose measured loss was above 80ml described it as moderate, and 14% of those losing under 20ml described theirs as heavy. Judgement runs wrong in both directions.

Which is why the boring thing works. A row of dates with a mark for the days you leaked is evidence; "I think mine are quite heavy" is not. The printable period tracker holds the start dates and the printable symptom tracker gives you a box a day for what actually happened; both print at home and store nothing anywhere. Two or three cycles of that turns an awkward appointment into a short one.

And if the real question underneath is whether any of this is ordinary, that is answered with the ranges in is my period normal.