So, you’ve made the switch to the Mooncup - hurrah! A healthier, greener, money-saving choice. But right now, instead of feeling smugly eco and leak-free, you might be thinking: “Why is my Mooncup leaking?” or even “Why won’t my Mooncup open?”
First off: don’t panic. You’re not doing anything “wrong”. Getting the hang of your Mooncup can take a couple of cycles, and leaks (or the cup staying a bit too folded) are usually part of the learning curve. The good news? With a few simple tweaks, your Mooncup will soon be sitting snug, doing its thing, and you’ll forget it’s even there.
What we mean by a “leak”
When we talk about a menstrual cup leaking, we mean actual leaks - menstrual blood making its way into your pants, period underwear, or liner. What doesn’t count? Those light streaks on the loo roll when you wipe. That’s just residual fluid from your vaginal walls and nothing to worry about.
While you’re finding your rhythm with the Mooncup, wearing a liner or period underwear can give you peace of mind.
Why your Mooncup might not be opening
The most common reason for leaks is your Mooncup not opening fully once it’s inside. Because it’s made from soft, medical-grade silicone (for your comfort), it sometimes stays folded instead of popping open straight away.
Here are a few reasons that might happen:
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The Mooncup is angled upwards, not back towards your tailbone.
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The fold you’ve chosen doesn’t “release” easily.
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Your vaginal walls are gently pressing the cup closed.
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The tiny air holes at the rim need a quick clean to let air in.
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You may be a little tense — your pelvic floor muscles can hold the Mooncup closed if you’re not fully relaxed.
How to help your Mooncup pop open
A Mooncup that’s fully open = a Mooncup that’s leak-free. If your Mooncup isn’t opening, try these little tricks:
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Switch up your fold: The punchdown or labia fold often makes it easier for the rim to spring open.
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Mind the angle: Point your Mooncup towards your tailbone, not straight up.
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Run a finger check: Feel around the base for dents or folds.
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Give a little tug: Pulling down gently can help the rim pop into place.
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Twist it: A small rotation at the base encourages the cup to open fully.
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Make space: Press a finger against the vaginal wall to give the rim more room.
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Clear the holes: Rinse the air holes at the rim — they help your Mooncup fill with air and expand.
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Relax first: Try inserting when your muscles are relaxed — in the shower, on the loo, or after a few deep breaths. It makes all the difference.
Picking the right size Mooncup
Your Mooncup comes in two simple sizes:
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Size A – if you’re 30 or over, or if you’ve given birth vaginally.
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Size B – if you’re under 30 and haven’t given birth vaginally.
Using the right size is key to getting that snug, leak-free fit. If the cup is too small, it may not form a proper seal.
Other reasons your Mooncup might leak
Even when your Mooncup is opening properly, leaks can happen if:
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It’s full: If your Mooncup is at capacity, it will leak. Empty it more often on heavier days.
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Placement is off: The Mooncup needs to sit just beneath your cervix so it can catch your flow.
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Seal isn’t formed: Run a finger around the base to check for a comfortable seal.
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Stem discomfort: If the stem feels uncomfortable, trim it (as per instructions). Comfort helps you insert with confidence and avoid leaks.
Position, practice, and patience
Every body is different. You might find the Mooncup opens more easily if you insert it in a certain position — squatting, sitting on the loo, or standing with one leg raised.
Empty your Mooncup a little more often at first while you learn your flow, and don’t worry if it takes a couple of cycles to feel natural. Once you and your Mooncup have figured each other out, it’ll be smooth sailing.
FAQs about Mooncup leaking and opening
Why is my Mooncup leaking when it’s not full?
If your Mooncup isn’t full but you’re still seeing leaks, it’s often because the cup hasn’t fully opened or it’s sitting slightly off-position. Make sure it’s angled towards your tailbone and sitting just beneath your cervix. A little twist or gentle tug can also help it pop open and seal.
How do I know if my Mooncup has opened properly?
You might feel a small “pop” when your Mooncup opens, but if you’re not sure, run a finger around the base. It should feel round and smooth, with no dents. If you notice a fold, gently adjust by pulling down or twisting the cup.
Can the wrong size Mooncup cause leaks?
Yes. Choosing the right size is important for a secure fit.
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Size A is recommended if you’re 30 or over, or if you’ve given birth vaginally.
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Size B is recommended if you’re under 30 and haven’t given birth vaginally.
If your Mooncup is too small, it may not form a proper seal, which can lead to leaks.
What if my Mooncup still leaks after trying everything?
Don’t worry – it usually takes a few cycles to get completely comfortable with your Mooncup. Keep experimenting with folds and angles, and double-check that the air holes are clear. Most people find that with a little patience, leaks become a thing of the past.
Final word: Practice makes perfect
If your Mooncup is leaking or your Mooncup won’t open right away, you’re not alone. Most people take a couple of cycles to find their groove. Once you’ve mastered insertion and sealing, your menstrual cup will feel like second nature — comfortable, secure, and reliably leak-free.
And that’s when you get to enjoy what the Mooncup is all about: freedom, comfort, and one small, powerful change for the planet.
Bottom line: Leaks don’t mean the Mooncup isn’t for you. With the right size, angle, and a little practice, your Mooncup will soon be your trusty, leak-free period pal.
Blog disclaimer
Our blog is intended to share information and ideas around periods, health, and sustainability. While we do our best to keep content accurate and up to date, things can change over time. The information here is not intended as medical advice — for any health-related concerns, please consult a qualified healthcare professional. For more information on our claims, please see our Claims Page, and for the most up-to-date product information, please visit our Product Pages.
