heavy flow
The Best Period Underwear for Heavy Flow and Overnight
Short answer
For heavy flow and overnight, choose a high-waist pair with a stated high capacity and an absorbent layer that runs to the back of the waistband. Kiri nightwear holds up to 75 ml, about 8.5 regular tampons, and is cut for lying down and side sleeping.
For heavy flow and overnight, the best period underwear is a high-waist style with maximum absorbency and padding that runs all the way to the back of the waistband — not just along the gusset. At Kiri that's the nightwear style, which holds up to 75 ml (about 8.5 regular tampons) and is cut so the coverage sits where the flow actually goes when you're lying down. Everything else about a heavy-day pair is a detail on top of those two things: capacity, and where the padding is.
Why heavy and overnight are really the same problem
A daytime pair is designed around sitting and standing, where gravity keeps the flow at the gusset. Lying down changes the geometry — flow travels backward toward the waistband, which is exactly where a standard cut stops absorbing. That's why people leak overnight in underwear that was perfectly fine all day: the capacity was there, but the coverage wasn't in the right place. Solving heavy flow and solving overnight turn out to be the same design fix.
What to look for in a heavy-flow pair
- Capacity you can quantify. Look for a stated millilitre figure, not a vague "heavy" label. Kiri nightwear holds up to 75 ml — roughly 8.5 tampons — so you can actually match it to your flow.
- Full back coverage. The padding should run gusset to waistband, front and back. This is the part that makes overnight and side-sleeping work.
- A high waist. Beyond coverage, a high-waist cut stays put through a night of moving around rather than shifting.
- A real leakproof shield. Capacity is pointless without a leakproof shield that keeps it off your sheets.
How Kiri's nightwear is built for it
Our nightwear panties use the same four bonded layers as the rest of the range — moisture-wicking top, antibacterial layer, absorbent core, leakproof shield — but scaled up: a 75 ml core and padding cut all the way to the back. The aim is simple: sleep through the night without waking up to check or change. Side sleepers are covered because the padding wraps front to back rather than running down the middle.
Using them on a heavy day (awake)
The same pair works through a heavy daytime flow. Worn on their own, they'll usually carry you through the day with one change — they're designed to be worn alone. If you want extra peace of mind on your very heaviest day, you can add a tampon or cup, but it isn't necessary.
How often to change on a heavy day
Change when the pair starts to feel full rather than at set times. On your heaviest day that might mean one change around midday and a fresh nightwear pair before bed. Rinse the used pair in cold water as soon as you can.
Small things that help on heavy nights
- Start the night fresh. Put on a clean nightwear pair just before bed rather than one you've worn since the evening.
- Get the fit snug. Nightwear is cut slightly closer than daywear; if you're between sizes, size down so it stays in place as you move.
- Sleep how you like. The absorbent layer wraps front to back, so side and back sleeping are both covered.
Building a rotation
Because heavy days need changing and washing more often, two nightwear pairs beat one — you're never waiting on a wash. The Nightwear duo and day-and-night bundles exist for exactly this, and they work out cheaper than buying pairs singly. One fitting note: nightwear runs a little tighter than daywear, so if you're between sizes, go down a size — the size guide has the measurements. Browse all our period underwear to see day and night side by side, or the full range for everything else.
When to talk to a doctor
Period underwear is built for heavy flow, but it isn't a fix for unusually heavy bleeding. If you regularly soak through protection every hour or two, pass large clots, or your period lasts longer than seven days, it's worth seeing a doctor.
Keep reading
Frequently asked questions
Why do I leak at night but not during the day?
Lying down sends flow backwards towards the waistband, where a daytime cut stops absorbing. Overnight pairs need the absorbent layer to run all the way to the back.
How much does Kiri nightwear hold?
Up to 75 ml, about 8.5 regular tampons, in a high-waist cut with absorbency from front to back.
What size nightwear should I choose?
Measure your waist and hips. Nightwear runs XS to XL and is cut slightly closer than daywear; if you are between sizes, size down so it stays in place overnight.
When should I see a doctor about a heavy period?
If you regularly soak through protection every hour or two, pass large clots, or your period lasts longer than seven days, it is worth seeing a doctor. Period underwear handles heavy flow but is not a fix for unusually heavy bleeding.
Can I sleep in daywear?
On a light night, yes. Daywear's absorbent layer doesn't run as far back, though, so for heavier nights choose nightwear.
Can I see the nightwear before buying?
Yes. It's on display inside Blomstre, Shop 401, 4/F C & D, Hopewell Mall, Wan Chai, open daily 12pm to 9pm.
Heavy Flow
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