Period Underwear in Perimenopause: What to Check Before You Buy

In perimenopause, periods can arrive early, late, light or suddenly heavy. Period underwear, washable briefs with a built-in absorbent layer, can be a comfortable backup on unpredictable days. A drawerful isn’t cheap, so here is what to know before you buy.

How the FDA classifies it

The FDA¹ treats period underwear as a type of menstrual pad that combines the absorbent features of a pad or liner with underwear.¹ Menstrual pads are regulated as medical devices. Before they can be sold legally in the U.S., makers must register and list the product with the FDA, follow its manufacturing and adverse event reporting rules, and meet its labeling requirements.¹

That doesn’t mean the FDA¹ tests each pair before it’s sold. Read the label and the maker’s instructions closely.

Checks before you buy

1. Match the absorbency to your flow. Brands use their own scales, so compare how much each style says it holds rather than names like “heavy” or “super.”
2. Plan to pair it on heavy days. The FDA² notes that products can be used together, such as a tampon or cup with something that absorbs outside the body.²
3. Read the care instructions first. The FDA¹ advises following the labeling, including cleaning instructions, and not reusing period underwear longer than the maker recommends.¹ Check whether you can machine wash or tumble dry, and how many washes the maker expects it to last.
4. Know what it’s made for. Period underwear is designed for menstrual flow. If you also leak urine, look for products labeled for bladder leaks. Our article on paying for bladder leak pads covers that side.
5. Buy one or two first. Test fit, comfort and how they hold up in the wash before you commit to a full set.

Wear and care

• Change regularly. The FDA’s¹ advice for pads is to change every few hours, even when flow is light, and more often when it’s heavy.¹
• Wash your hands before and after changing.¹
• Watch your skin. If you notice itching, rash, pain, swelling or discomfort, stop using the product and contact your healthcare provider.¹

What about chemicals?

Questions about substances in reusable menstrual products are still being studied. A 2025 study found plastic additives such as phthalates in both single-use and reusable menstrual products, including menstrual underwear. Its risk estimates assumed a worst-case scenario in which the skin absorbed 100% of these chemicals, which the authors noted may not reflect everyday use.³ If this matters to you, ask the maker what the absorbent layers are made of and whether they’re tested for added chemicals.

When soaking through means a visit

Period underwear helps with leaks. It doesn’t treat the cause of heavy bleeding. If you’re soaking through protection quickly, passing large clots, bleeding longer than usual, or feeling tired and short of breath, talk with a clinician. Our article on how to tell if a period is too heavy lists the signs. Any bleeding after you’ve gone 12 months without a period needs to be checked.

Try: “My periods in perimenopause have become heavy and unpredictable, and I’m soaking through period underwear and a tampon together. What could be causing it, and what are my options?”

Period, Handled includes a Period Scorecard and a visit script. Use them to record how often you change products on heavy days, so your clinician sees how much you’re bleeding. See the book.