Key Takeaways

• "Won't pop open" and "turned inside out" are different problems with different causes and different fixes.
• A cup that hasn't opened is still correctly shaped — it just needs help releasing.
• A cup that's inside out needs to be manually reshaped before reinsertion.
• Both issues are common in the first few cycles and typically resolve with practice.
• The base-check (running a finger around the rim after insertion) catches opening problems early, before they turn into a full-day issue.

Problem 1: The Cup Won't Pop Open

What's Actually Happening

During insertion, the cup is folded into a narrower shape. Once inside, it's supposed to unfold and spring back into its full round shape, creating the seal against the vaginal walls. Sometimes it stays partially or fully folded instead of releasing, usually because the fold wasn't fully released during insertion, or because the insertion angle didn't give it enough room to naturally unfold.

How to Tell This Is What's Happening

Run a finger around the base of the cup (not the stem). If you feel any flat or folded section along the rim, rather than a consistently round shape, the cup hasn't opened. This is different from the cup being correctly round but just sitting in an uncomfortable position — this check specifically confirms shape, not position.

The Fix, Step by Step

1. Rotate the Cup

Using clean fingers, gently turn the cup a half-rotation in either direction. This motion often releases a stuck fold simply through the mechanical movement, even without directly touching the folded section.

2. Run a Finger Around the Entire Rim

Trace the full circumference with one finger, feeling for and gently releasing any remaining folded or flattened section as you go.

3. Gently Pull Down Slightly (Not Out)

A small, controlled downward pull — not a full removal attempt — can sometimes create just enough space and air movement for the cup to pop fully open, after which it will usually settle back into a secure position on its own.

4. Try a "Pinch and Release" at the Base

Gently pinch the base of the cup between two fingers and release. This small compression-and-release action can sometimes trigger the pop that insertion alone didn't achieve.

5. Recheck With the Base Test

After trying the above, run your finger around the rim again to confirm it's now fully round before considering the cup properly placed.

If It Still Won't Open After Trying These

Remove the cup entirely, make sure it's clean, and try reinserting with a different fold technique. Our fold techniques guide covers the punch-down and 7-fold as alternatives to a basic C-fold, and switching folds often resolves a persistent opening issue that a single fold technique keeps running into.

Problem 2: The Cup Has Turned Inside Out

What's Actually Happening

This is a different, though related, issue. Rather than simply staying folded, the cup's rim has collapsed inward on itself, essentially flipping the cup's shape — the opening edge folds into the cup's interior rather than remaining as an outward-facing rim.

This happens most commonly during removal, particularly if the seal is broken in a way that causes the rim to collapse inward rather than release cleanly, though it can occasionally happen during insertion with certain fold techniques too.

How to Tell This Is What's Happening

This is usually visually obvious once the cup is out. Rather than looking like its normal cup shape, it appears folded in on itself, sometimes resembling a smaller, denser shape rather than an open vessel. If you're unsure, compare it to how the cup looks when you first take it out of its original packaging or storage pouch — that's the correct, "right-side-out" shape to compare against.

The Fix, Step by Step

1. Don't Try to Reinsert It in This Shape

A cup that's turned inside out won't function correctly if inserted this way — it needs to be corrected first.

2. Gently Reshape It With Clean Hands

Using your fingers, gently push the collapsed rim back outward, working around the circumference gradually rather than trying to force the whole shape back at once. Take your time with this — rushing can cause you to push unevenly and create a different, equally unhelpful shape.

3. Compare It to Its Normal Resting Shape

Once reshaped, it should look like a consistent, open cup — similar to how it looked when new or freshly cleaned, with a smooth, round rim and no inward folds remaining.

4. Rinse and Recheck Before Reinserting

Once properly reshaped, give it a clean rinse (or a full sterilize if you have the time and it's a natural point in your routine) before reinserting, since handling it extensively with your hands during the reshaping process is worth following up with a clean rinse.

Why This Happens More Often During Removal

This typically occurs when the seal is broken abruptly, rather than gradually — for example, pulling or tilting the cup sharply right as the seal releases, which can cause the rim to collapse inward rather than simply releasing and maintaining its shape.

Our removal guide covers the "pinch the base, don't pull the stem" technique in detail, and following this specific method can help reduce how often a cup turns inside out during removal.

How to Prevent Both Issues Going Forward

A few consistent habits meaningfully reduce how often either of these problems comes up after your first few cycles of practice.

For Preventing "Won't Pop Open"

• Always do the base-check immediately after every insertion, not just when something feels off. Catching it early means a quick fix rather than a surprise leak hours later.
• Experiment with fold technique in your first few cycles rather than assuming your first fold is the only option.
• Pay attention to insertion angle. Aiming slightly toward your lower back or tailbone, following the natural curve of the vaginal canal, gives the cup more room to unfold properly than inserting too straight.

For Preventing "Turned Inside Out"

• Always break the seal fully before attempting to remove the cup. Pinch the base first, confirm you feel the seal release, then proceed with removal.
• Remove slowly and steadily rather than pulling quickly, which gives the rim time to maintain its shape as it comes out.
• Keep the cup relatively upright during removal rather than tilting it sharply, which can contribute to inward collapse.

Is Either of These a Sign Something's Wrong With the Cup Itself?

Generally, no — both issues are far more commonly related to technique and the learning curve than to any flaw in the cup itself, particularly in the first several cycles of use.

That said, if either issue happens persistently, cycle after cycle, despite trying the fixes and prevention tips above, it's worth checking the cup for any signs of wear affecting its flexibility. A cup that's lost some of its original flexibility due to age or improper storage can be more prone to these issues than a cup in good condition. Learn more in our menstrual cup lifespan guide.

Frequently Asked Questions

Is It Dangerous If My Cup Turns Inside Out While It's Still Inside Me?

This is generally a functional issue rather than an emergency. The cup may not seal properly in that shape, which can increase the risk of leaking. If you experience pain, difficulty removing the cup, or persistent discomfort, stop and seek medical advice rather than forcing it.

How Often Should I Be Doing the Base-Check — Every Single Time, or Just When Something Feels Off?

Every time, ideally, especially in your first several cycles while you're still building confidence and consistency with insertion. It takes only a few seconds and can catch an incompletely opened cup before it becomes a bigger problem later in the day.

Can a Cup Turn Inside Out Just From Normal Movement During the Day, Not Just During Removal?

This is uncommon. A cup changing shape is more strongly associated with insertion or removal than with everyday movement, sitting, or walking. If you repeatedly notice the cup changing position or shape, review your technique and consider speaking with a gynecologist.

Does This Happen More With Certain Fold Techniques Than Others?

It can vary by individual, but a punch-down or 7-fold, which create a narrower profile with a more defined release point, sometimes open more reliably than a basic C-fold for people who experience frequent "won't open" issues. This varies from person to person, which is why trying alternatives is worth it.

If My Cup Keeps Not Opening Properly Even After Trying Everything, Could It Be a Sizing Issue Instead?

It's possible, particularly if you've tried multiple fold techniques and insertion angles without success. A cup that's a significant size or firmness mismatch for your body can sometimes struggle to open fully regardless of technique, and revisiting sizing is a reasonable next step. A gynecologist or qualified menstrual health educator can help you assess your options.

The Real Takeaway

Both of these issues feel alarming in the moment, especially early on, but they're genuinely common, well-understood, and often fixable — not signs that something's gone wrong or that cups "aren't working" for you.

A cup that won't open just needs a little help releasing from its fold. A cup that's turned inside out just needs to be gently reshaped before going back in. Neither requires panic, and both can become noticeably less frequent with practice and the right base-check habit.

TESSA's cup is designed to open reliably and hold its shape through correct use, but even well-designed cups depend on getting a few fundamentals right. If you're building your technique from scratch, pair this guide with our beginner's guide and fold techniques guide for the complete picture.