What GB/T 39391-2020 Actually Says About Period Pants

When I first saw a pair of period pants labeled "executes GB/T 39391-2020," I had to laugh a little. Most buyers don't even know that code exists. They just want to know if the thing will hold up through the night. But that string of numbers is actually the reason you can trust the "holds up" claim at all.

GB/T 39391-2020 is China's national standard for female sanitary pants — basically any pant-style product built for menstruation, the category most of us call period pants, overnight pants, or comfortable menstrual pants. Before this standard came out in 2020 and took effect in June 2021, a lot of these products were tested under the older pad standard GB/T 8939. That never made sense. A pad and a pant are worn differently, leak differently, and fit differently. The 39391 standard finally treats them as their own product class.

What the standard actually checks

The standard splits its requirements into a few practical buckets. Here's the part worth knowing before you buy:

• Absorption speed: The test liquid has to be absorbed in ≤60 seconds. That's measured with a device that mimics real use better than the old beaker-and-stopwatch setup. If a pant takes longer, surface wetness becomes a problem fast.
• pH: 4.0 to 9.0. Skin in that area is naturally slightly acidic, so anything outside this band can irritate.
• Formaldehyde: ≤75 mg/kg. Same limit as the pad standard.
• Migratable fluorescent agents: Must not be detected. This matters because recycled or cheaply bleached fibers sometimes carry optical brighteners that have no business near skin.
• Delivery moisture: ≤10.0%, but that's checked at the factory gate, not in your bathroom drawer.
• Size and fit: The standard defines S, M, L, XL by hip circumference and maximum waist stretch — not by weight. A lot of brands still label "for 50-60 kg," but GB/T 39391 wants the actual centimeters on the pack.

It also says that if a pack contains five pieces or more, each piece should be individually wrapped. Hygiene counts.

Why this matters for B2B buyers too

If you're sourcing OEM period pants, asking whether the factory tests against GB/T 39391-2020 is a quick sanity check. A supplier that only quotes GB/T 8939 for a pant-style product may not even have the right test fixtures. The same standard underpins our guides to period pants for postpartum recovery and for sport, where fit and absorption speed are non-negotiable. We've seen samples that looked fine in photos but failed the 39391 absorption-speed test because the acquisition layer was too thin. The standard gives you a shared language to catch that before production.

That said, GB/T 39391 is a recommended national standard (the "T" in GB/T), not a mandatory law. A product can legally be sold without claiming it. But when a brand does claim it, and the package shows the right hip-range labeling, it's a sign the factory took the product category seriously.

How to read the label

Look for these five things on the pack:

1. Product name includes "女性卫生裤" or the English equivalent.
2. Standard number: GB/T 39391-2020.
3. Hip circumference range, in centimeters.
4. Main raw materials.
5. Production date / shelf life and the producer's contact details.

If the pack only says "fits 45-65 kg" and nothing about hip measurement, the sizing guidance is weaker than what the standard recommends. That doesn't make the product unsafe; it just means you might get a tighter fit than expected.

FAQ

Last note: Standards evolve. We wrote this against GB/T 39391-2020, the version in force at publication. If a newer revision appears, we'll update.