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Knowledge is power. Learn how your cycle affects everything, from your skin to your relationships.
99 articles
Perimenopause age: when does it start, and how early?
What age does perimenopause start? Usually in your mid 40s, sometimes earlier. What is normal at each age, what brings it forward and when to see a doctor.
Best menopause app 2026: 6 apps compared honestly
Looking for a perimenopause or menopause app? We compared Balance, Caria, Clue, Flo, Stella and PERIOD. meno on features, price and privacy.
PMDD symptoms: signs, cause and what helps
A week of despair, rage or low mood every month, gone once your period starts? That can be PMDD. The symptoms, the diagnosis and what helps.
Perimenopause symptoms: every sign, with a checklist
Everyone knows hot flushes, but perimenopause often starts with something else: a changing cycle, poor sleep, forgetting words. Every symptom at a glance and when to see your GP.
Vaginal discharge: what is normal in each cycle phase?
White, clear, stretchy like egg white or brown: discharge changes all month. What is normal in each phase, what it says about ovulation and when to see your GP.
Blood clots in your period: when are they normal?
Small clots on your heaviest days are usually normal. When clots point to heavy periods, what causes them and when to see your GP.
Ovulation pain: what is it and how long does it last?
A sharp or dull pain on one side of your lower belly, mid cycle? That is often ovulation pain. How long it lasts, what helps and when to see your GP.
How long does a period last? And when is it too long
A period usually lasts 3 to 7 days. What is normal, why it varies month to month, and when a long or short period is a reason to see your GP.
Hot flushes: what is happening and what helps?
Hot flushes are part of menopause, but you do not have to just sit them out. What a hot flush is, how long they last, what sets them off and what really helps.
Perimenopause, menopause, postmenopause: what is the difference?
Perimenopause, menopause and postmenopause get mixed up. What each one means, at what age it usually happens and how to know where you are.
Tracking your HRT: why it helps and how to do it
Gel, patch, tablet or spray, often with progesterone: HRT can be a puzzle. How to keep track of what you use and how you feel, for yourself and your GP.
Seeing your GP about menopause: how to prepare
Ten minutes with your GP is short for hot flushes, sleepless nights and a cycle all over the place. With this preparation you get more out of the appointment.
Periods at work: what can employers do?
Many women work through period symptoms, and some call in sick because of them. Five things employers can do, without making it awkward.
Menopause at work: how to support colleagues
Hot flushes, poor sleep and trouble concentrating often land in the middle of a career. What helps colleagues in menopause and what employers can put in place.
ISO 45010 explained: what it asks of employers
Since September 2026 there is an international guidance standard for menstruation and menopause at work. What is in it, what it is not, and how employers can start.
When will I get my period? How to work it out
When is your next period due? Work it out from your own cycle length, learn why the date sometimes shifts, and when to see a doctor.
Two periods in one month: is that normal?
Two periods in one month? Often it is simply a short cycle. How to tell it apart from bleeding between periods, and when to see a doctor.
How to use an ovulation test: when to test, how to read it
When to start an ovulation test, what time to test, and when it is really positive. How LH works, your fertile days, and what the test cannot tell you.
How long does it take to get pregnant?
Most couples conceive within a year. What the numbers say, what improves your chances, the role of age, and when to see a doctor.
Early signs of pregnancy: what you notice first
A missed period, tender breasts, nausea or tiredness: the first signs of pregnancy, when they start, and when to take a test.
Flo vs Clue vs Natural Cycles (2026): an honest comparison
Flo, Clue and Natural Cycles side by side: what they cost, where your data goes, what they can and cannot do. With sources, as of October 2026.
Best period tracker app for privacy in 2026: 6 questions that decide it
Which cycle app is safest for your data? Six questions to test any app in two minutes, plus how Flo, Clue, Natural Cycles and PERIOD. compare.
Best free period tracker app in 2026: what is really free?
Many cycle apps call themselves free but put the basics behind a subscription. Here is what you really get for free with Flo, Clue, Natural Cycles and PERIOD.
Best app for period and ovulation tracking (2026)
Tracking your period and ovulation in one app: what an app can and cannot know, which measurements really help, and how Flo, Clue, Natural Cycles and PERIOD. approach it.
Looking for a Flo alternative? A European period app that does not sell your data
Looking for an alternative to Flo? What you take with you, what to check when switching, and why more women choose a European app.
Is PERIOD. free? What the app really costs (and what it does not)
Short answer: yes. Tracking your cycle, predictions and reminders cost nothing. Plus and baby are extras. Here is exactly what is what, no fine print.
Does my period app sell my data? How to check in 5 minutes
Short answer: you cannot tell from the app itself, but you can from the privacy policy and the trackers. Five checks you can do yourself, on any cycle app, including ours.
Trying to conceive: when do you switch from a cycle app to a pregnancy app?
Short answer: preferably never. The moment you switch is exactly when your cycle data is worth the most. What you lose, what you need, and how it fits in one app.
Cycle app on the pill: is tracking still worth it when you use contraception?
Short answer: yes, but for a different reason than you think. On the pill you do not predict ovulation, but you do track complaints, bleeding and what happens when you stop.
How do I delete my cycle data from an app? Step by step, for any app
Short answer: in the EU you have the right to have everything erased, and the app must make that possible. Here is how at the app you use now, and how at ours.
Planning your work week around your cycle: practical, not woo
Plan presentations, deadlines and meetings around your own energy pattern. What works, what you can raise with your employer, and what stays private.
Cycle data is special category data: what that means for you
Your period data falls under the strictest category of the GDPR. Which rights that gives you, and how to use them in five minutes.
Cycle syncing: does it actually work, or is it mostly TikTok?
Training, eating and working in sync with your cycle phase. What holds up scientifically about cycle syncing, what does not, and how to apply it.
Our privacy policy in plain language, the 2-minute version
Our full privacy policy is thorough, but long. Here's the same content in plain language: what we do and don't do with your data, in 2 minutes.
Heat and your cycle: why a heatwave can make your symptoms feel heavier
Tropical nights, more headaches, worse sleep around your period? Not a coincidence. This is how heat and your cycle interact, and what actually helps.
Switching cycle apps: how to take all your data with you
Your cycle history is worth keeping, so do not leave it behind. How to request an export, use your GDPR rights and start in PERIOD. without losing your history.
Samsung Health vs PERIOD.: cycle tracking on Android compared
Samsung Health has built-in cycle tracking, with temperature-based predictions via the Galaxy Watch. When is that enough, and when do you want more? An honest comparison.
The Dutch privacy watchdog warns about period apps, and Editie NL names PERIOD. as the European alternative
The Dutch Data Protection Authority warned about cycle-tracking apps this week. RTL 4 / Editie NL covered it and named PERIOD. as the European, transparent alternative. Here is exactly what the regulator said, and what you can check yourself.
Apple Cycle Tracking vs PERIOD.: what the built-in tracker can and cannot do
Every iPhone has cycle tracking built into the Health app. When is that enough, and when do you want more? An honest comparison, including the point where Apple beats us.
The Dutch privacy watchdog warns about period apps: what is going on (and what to check yourself)
The Dutch Data Protection Authority urges caution with period apps and does not rule out an investigation. What exactly did the regulator say, why now, and how do you check your own app in five minutes?
PERIOD. in TechRound: can femtech put women back in control of their own data?
UK tech title TechRound interviewed Lisa Volkers about cycle data, business models and why collecting less beats writing a longer privacy policy.
PERIOD. in How About Mom: 'I came to learn, not to close pop-ups'
How About Mom interviewed Lisa Volkers about why she built PERIOD.: no pink pop-ups, no unsolicited pregnancy nudges and no data as a business model.
Tracking your cycle with a smartwatch or ring: how accurate is it?
Apple Watch, Oura and other wearables measure skin temperature during sleep to estimate ovulation. What they can and can't do, and what happens to that data.
PERIOD. in De Ondernemer: from 0 to 50,000 users in 5 months
Dutch business title De Ondernemer interviewed Lisa Volkers and Diederick Trampe about PERIOD.'s growth, cycle awareness at work, and why we will never sell your data.
Missed period and not pregnant: 10 possible causes
Your period is missing but the test is negative. From stress and weight change to PCOS, thyroid issues and contraception: the most common causes and when to see a doctor.
Supplements for PMS: what actually works, according to research?
Calcium, vitamin B6, magnesium, vitamin D, omega-3 and chasteberry: how strong is the evidence for each in PMS, and where to be careful.
Menstrual cup, tampon or period underwear: which suits you?
An honest comparison of menstrual cups, tampons, pads and period underwear: capacity, cost, wear time, safety and environmental impact. No marketing spin.
Heavy periods and iron deficiency: when is bleeding too much?
How much blood do you normally lose during your period, when is it 'heavy', and why do heavy periods so often cause iron deficiency? With concrete warning signs and what to do.
PERIOD. in Het Financieele Dagblad: cycle apps, millions raised, and intimate data
Het Financieele Dagblad wrote about cycle apps raising millions on intimate information. PERIOD. is mentioned as the Dutch, privacy-first alternative. What the piece means, and why we're glad it exists.
Menstrual leave in the Netherlands: why the conversation is happening now
Spain became the first EU country to introduce paid menstrual leave in 2023. France, Belgium and the Netherlands are now debating. What would it mean, and what do the numbers say?
Seed cycling: does it actually work, or is it a TikTok trend?
Flax and pumpkin seeds in phase 1, sesame and sunflower in phase 2, seed cycling is everywhere on TikTok. What does the evidence say, and is it worth it?
Cortisol, stress and your cycle: what the TikTok hype gets right and wrong
'Cortisol face', 'cortisol belly', cortisol mocktails, TikTok is obsessed with cortisol. What does stress actually do to your cycle, and which claims can you throw out?
Comparing period apps in 2026: what actually matters
Privacy, core features, paywalls and language: the eight questions that let you judge any cycle app in five minutes — including our own answers.
Ozempic, Wegovy and your cycle: what GLP-1 drugs do to your hormones
More and more women on GLP-1s report changed cycles, unexpected pregnancies or returning ovulation with PCOS. What do we actually know, and what's speculation?
Perimenopause in your 30s: why the conversation is finally happening
Perimenopause can start in your late 30s, years before 'real' menopause. Here are the early signals, what your cycle is telling you, and why generations of women missed this.
A cycle app that doesn't sell your data: how do you actually know?
Every app promises 'privacy'. But what should you look for in a privacy policy to check if it's really true? 6 concrete things to watch.
Inc. Magazine quotes PERIOD.: how founders use AI to stress-test their idea
US Inc. Magazine spoke with founders, including PERIOD.'s Lisa Volkers, about using AI as a hostile sparring partner instead of a cheerleader.
Contraception and cycle tracking: what can you still see if you're on the pill?
On hormonal contraception you technically don't have a real cycle anymore. But tracking can still be useful, for symptoms, not for predictions.
Your cycle after childbirth: when does your period return?
Breastfeeding or not, real period or breakthrough bleed: here's what postpartum cycles typically do and what to expect.
Breast tenderness before your period: why it happens and what helps
Tender, swollen or painful breasts in the week before your period? Here's what's happening hormonally, and what actually brings relief.
Postponing your period: what's safe and what isn't
Holiday, wedding, big race? Here are the ways to postpone your period, what works, the risks, and what to avoid.
Implantation bleeding or period? How to tell the difference
Light bleeding around the time your period is due? Here's how to tell implantation bleeding apart from a regular period, and when to test.
Calculating ovulation: how to find your fertile window
When exactly is your ovulation? Calculate it from your cycle length, and learn why your body is often a better predictor than any formula.
Why you suddenly sleep badly in week 4: cycle and sleep explained
Right before your period, your body temperature, heart rate, and melatonin shift. No wonder you're awake. What you can do about it.
Basal body temperature: what it tells you about your cycle (and what it doesn't)
A cheap thermometer and three minutes each morning can tell you a lot about your cycle. But BBT mostly confirms, it doesn't predict. Here's how to use it smartly.
Coming off the pill: what your cycle does in the first months
No period, sudden acne, irregular cycles, hormonal mood shifts, what your body does after you come off the pill, and what's worth flagging to a doctor.
PMS or PMDD? How to tell the difference
Everyone has a rough premenstrual week now and then. But if that week derails your life every month, we're not talking about 'just' PMS anymore. Here's the difference, and what to do.
Brown discharge: when it's normal and when to see a doctor
Brown discharge is usually old blood that took its time to leave the body. There are moments, though, when it's worth paying attention. An honest overview.
Can you get pregnant on your period? The honest answer
Some sites say 'no', others say 'yes'. The real answer is: rarely, but it can happen, especially with short or irregular cycles. Here's exactly when and why.
Ovulation symptoms: 8 signs your egg is on the way
Egg-white cervical mucus, a tiny dip in basal body temperature, a one-sided twinge low in the abdomen, your body usually signals ovulation clearly. Here are the signs you can actually trust.
Nutrition during your cycle: what your body actually needs in each phase
Cycle syncing sounds like hype, but there's a kernel of truth: your needs for iron, energy, and protein change in each phase. Here's a practical guide.
PERIOD. on BNR's De Grote Tech Show: 'We figure out how to safely manage your intimate data'
Lisa Volkers and Diederick Trampe were guests on De Grote Tech Show on BNR Nieuwsradio, with Joe van Burik and Ben van der Burg. About privacy, vibecoding and racing toward 100,000 users.
Irregular periods: 8 causes (and when it stops being 'just stress')
A cycle that varies month to month is normal. But if it disappears for months or becomes extremely short, something is usually going on. 8 causes listed.
PCOS explained: what it is, how to recognize it, and what tracking has to do with it
PCOS affects 1 in 10 women, but many diagnoses come after years of unexplained symptoms. An honest explanation, without panic or oversimplification.
Recognizing endometriosis: 7 signs that aren't 'just a heavy period'
1 in 10 women have endometriosis, but diagnosis takes 7-10 years on average. We list 7 signs that do warrant a conversation with your doctor.
Exhausted during your period? Here's what's happening in your body
You sleep 9 hours and you're still wrecked. Not a coincidence. On day 1 and 2, estrogen and progesterone both drop, your body is running on reserves.
Spotting between periods: 6 causes (from harmless to 'call your doctor')
A spot of blood outside your period can be ovulation, contraception, stress, or something that needs investigating. We list the causes.
Menstrual migraine: why your headache always shows up on day 1
Hormonal headaches come 2 days before or during the first 3 days of your period. It's not in your head, it's an estrogen dip. Here's what helps.
Relieving period cramps without painkillers: what actually works (according to research)
Heat pad, ginger, magnesium, yoga, what's hype and what actually has studies behind it? We check 8 popular methods against the evidence.
Recognizing PMS symptoms: 12 things that aren't a coincidence
Crying at commercials, suddenly craving chocolate, getting irritated over nothing, if it happens 7-10 days before your period, it's probably PMS.
Tracking your period for the first time? Start here (without it becoming a project)
Cycle tracking doesn't have to be a second job. With 3 things per day, you'll have a good picture of your body within 2 months. Here's the minimalist starter menu.
How to recognize ovulation: 5 signs that actually matter
Ovulation tests, basal body temperature, cervical mucus, there are countless ways to track ovulation. But which are actually reliable? We go through the 5 most important signs.
The luteal phase explained: why you can't stand anyone in week 4
The luteal phase is the second half of your cycle, after ovulation. Progesterone rises, energy drops, and everything feels a bit heavier. Here's why, and what helps.
The follicular phase: why you feel like a superhero on day 7
The follicular phase is the first half of your cycle, after your period. Energy rises, focus improves, skin calms down. Here's what's actually happening hormonally.
What is a normal menstrual cycle? (and when is 'something weird' actually normal)
A 'normal' cycle lasts between 21 and 35 days. But what does that really mean, and when should you actually worry? We explain it without the pink illustrations.
Why tracking your cycle does more than just predict your period
Tracking your cycle is about much more than knowing when your period is coming. It reveals patterns that change how you live.
Finally! PERIOD. is now on Android too
After three weeks of back-and-forth with Google, PERIOD. is now live on the Play Store too. A short recap of what it means.
The one thing no one tells you about cycle syncing your workouts
You don't have to train the same way every week. In fact, you probably shouldn't. Here's how your cycle affects your strength, endurance, and recovery, and how to use it.
Your cycle has four phases, here's what each one actually does to you
You're not the same person every day of the month, and that's not a weakness. It's biology. Understanding your four cycle phases might be the most useful thing you learn this year.
The two weeks nobody explains: how your hormones affect your feelings
Do you often feel down, anxious, or irritable in the two weeks before your period? Discover what the luteal phase is and why you feel this way.
The real reason behind your bad skin, energy dips and fluctuating libido
Spending hundreds on skincare without results? Discover how your menstrual cycle affects your skin, energy levels, and libido.
Flair (Belgium) features PERIOD.: on the luteal phase and cycle apps
Belgian magazine Flair spoke with our founder Lisa Volkers about PERIOD. the luteal phase, and why a privacy-first cycle app was needed.
Het Parool on PERIOD.: 'I don't want money to be made from women's data'
Het Parool published a feature on PERIOD. privacy, and why commercial period apps run on a business model most women don't know about. A short summary, and our take.
Radar (AVROTROS): "Your Intimate Data Isn't Safe With Popular Period Apps"
AVROTROS Radar investigated how popular period apps handle the data of one million Dutch women. Our response and why we built PERIOD.
Privacy at PERIOD. vs. other cycle apps, explained in plain language
What we do and don't do with your intimate cycle data, and how that differs from big tracker apps. A transparent explainer based on our actual privacy policy.
Why your relationship suddenly falls apart (and it's not your fault)
Do you sometimes feel irritable or distant towards your partner or friends? Discover how the luteal phase affects your relationships.
VICE on PERIOD.: "You Know When You Bleed, But Not Why"
VICE published an in-depth piece on how cycle apps profit from your intimate data, and why PERIOD. does things differently. Here's our take.
765,000 people in the Netherlands: what the CODE ROOD study tells us about period poverty
The 2024 CODE ROOD study by Neighborhood Feminists reveals how widespread period poverty really is in the Netherlands. The numbers, the context, and what you can do.
Why the basics of PERIOD. stay free, and how that actually works
We made a promise: the basics of PERIOD. stay free. No paywalls for knowing your own body. Here's the model behind it, and why it makes us different from every other period app.