Period Underwear for Heavy Flow and What to Look For

The best period underwear for heavy flow should combine high absorbency, enough coverage, a snug fit and a fabric you feel comfortable wearing for hours. At THATDAY, there are three heavy flow styles to choose from. Ella boxers are made for busy, active days, while Kima and Lola briefs are designed for your heaviest days and nights.

If your period has a day or two when you find yourself changing much more often than usual, period underwear can still be an option. The key is choosing a pair made for heavier flow and knowing when it’s time to change.

Not sure which absorbency you need? Start with how to choose period underwear for your flow, then come back here.

How do you know when to choose heavy flow period underwear?

Heavy flow period underwear makes sense on the days when you normally reach for super tampons or night pads, or find yourself changing more often than on the rest of your period.

Your flow can change throughout your cycle, so you may only want heavy absorbency for one or two days and switch to medium or light period underwear as your flow becomes lighter.

Can period underwear really handle a heavy flow?

Yes, period underwear designed for heavy flow can be used on heavier days, but how long one pair lasts depends on your individual flow.

THATDAY Ella boxers hold up to the equivalent of 6 regular tampons and are made for heavy flow. Kima and Lola are also designed for your heaviest days and nights.

Every pair has the same three-layer construction. A top layer pulls moisture away from your skin and dries fast, an absorbent core sits in the middle and a waterproof but breathable layer is on the outside. The fabrics are OEKO-TEX certified and each pair is handmade in Latvia.

On your very heaviest day you can also wear a tampon or menstrual cup together with your period underwear for extra peace of mind. Just skip the pad on top, since it takes away the comfort.

What should you look for in heavy flow period underwear?

Look at these four things before you buy.

• Heavy flow absorbency. Check that the pair is actually made for heavy flow rather than choosing based on the cut alone.
• Coverage that suits your day. Boxers and high-rise briefs give you more coverage, while a mid-rise feels more like your everyday briefs.
• A snug fit. Period underwear works best when it sits close to your body. THATDAY pairs run a little small because of the extra layers, so if you’re between sizes, go one size up.
• A fabric you love wearing. Some people love the softness of cotton, while others prefer a smooth, sporty stretch fabric. That part is personal.

Ella, Kima or Lola, which heavy flow pair is right for you?

All three are made for heavy flow. The difference is the cut, the fabric and the moments they feel best in.

Ella super absorbent period boxers are the pair we made for moving. They hold up to the equivalent of 6 regular tampons, stay in place when you’re on the go and look smooth under leggings or a fitted dress.

Kima and Lola are soft cotton briefs for the days and nights when your flow is at its strongest. Kima comes up high over your tummy, while Lola sits lower on the hips.

What should you wear on heavy nights?

For heavy nights, go for Kima or Lola. Both are soft cotton styles made for heavy flow. Choose Kima if you like more coverage over your tummy or Lola if you prefer a mid-rise fit.

Put on a fresh pair right before bed and change it in the morning. If your nights are especially heavy, you can wear a menstrual cup or tampon with your period underwear too.

And if you’re completely new to period underwear, a quiet night at home can be an easy time to try your first pair.

Can you work out on a heavy day?

Yes, and that’s exactly what Ella was made for. The boxer shape stays put while you squat, run or stretch, so you can focus on your workout instead of your flow.

Here’s a short gym clip in Ella on a period day if you want to see it in action.

Thinking of swimming? You can swim in period underwear, but we don’t recommend it on heavy flow days, because the absorbent layers soak up water as well as menstrual fluid. Your THATDAY pairs are happiest on land, at the beach or by the pool.

How often should you change period underwear on a heavy day?

Change it when it starts to feel full. One pair can be worn for up to 8 to 10 hours depending on your flow, but on your heaviest day that might be sooner.

You may want to change once during the day and again before bed. If you start to feel a little moisture, that’s your cue to swap.

Out and about? Take a spare pair with you and pop the used one into a waterproof zipper pouch until you get home.

How many heavy flow pairs do you need?

Most people start with 2 to 3 pairs per cycle in total.

If you have one or two heavier days, two heavy flow pairs are practical, so you always have a fresh pair while the other one is being washed and dried. A medium flow pair can then cover the lighter days around them.

Not sure yet? You can try your first pair with our 40-day risk-free trial. If it’s not for you, send it back within 40 days for a full refund.

How do you wash period underwear after a heavy day?

Rinse it in cold water first, then machine wash at 40°C with your other clothes. Skip fabric softener and chlorine bleach and let it air dry.

Heavy flow pairs can take a little longer to dry than lighter ones, so give them time.

You’ll find the full routine in how to wash period underwear.

So, which heavy flow period underwear should you choose?

Pick Ella for busy, active heavy days and workouts. Pick Kima or Lola for your heaviest days and nights, choosing high-rise or mid-rise depending on what feels better for you. Start with two heavy flow pairs and add a medium flow pair for your lighter days.

Find all three in our Heavy Flow collection.

Frequently asked questions