Why you should delete your menstrual cycle app now

My Hormonology

Why you should delete your menstrual cycle app now



  • Menstrual cycle tracker apps may be a convenient way to keep tabs on your period, ovulation and other facets of your cycle. Unfortunately, you may be giving up your privacy for this convenience.


UPDATED MAY 4, 2022 (originally published January 18, 2020)—When I update a post, I typically do so to add recent studies, relevant news or useful tips. I don’t usually point out all the parts that I add since they’re not extremely important. The update to this post, however, is different. Please read my entire original post below. But, I’m placing my addition to the top of this post so it can’t be missed. It’s that important. Here’s what I’d like to add today:

If your menstrual cycle tracker app can access your data, it may be able to detect pregnancy. There have been recent changes in laws and protections within the United States regarding a woman’s right to choose as well as laws that have deputized private citizens to sue those providing reproductive care to patients. And, there are restrictive laws about reproductive freedom in other parts of the world. This means that if others get information that you’re pregnant through your app, you could be at risk of being surveilled or harassed.

That’s because when you agree to allow menstrual cycle tracker apps to access your data in their terms and conditions, you may not know where your data ends up. Your personal information (your menstrual cycle calendar or diary notes, for example) could be deliberately shared with third parties. Or, your information could be accessed surreptitiously by unscrupulous contractors, organizations or people somehow affiliated with the app developers or the company that oversaw creation of the app.

The bottom line: If you aren’t comfortable with strangers potentially knowing your pregnancy status, and you are not certain if an app protects your privacy, consider deleting that app.

As a reminder, all of my Hormonology apps (Hormone Horoscope and Female Forecaster apps) are 100% private. They were built in a way that no one–not me nor my app team–can access. And, I don’t have advertising on any of my apps, so they aren’t accessed in this back-door type of way, either.

That said, I encourage everyone to track their menstrual cycles on paper for 100% privacy. I created a paperback journal for this, my Hormonology Menstrual Cycle Tracker Journal, which is available at Amazon. But, you can use a regular notebook, a “bullet journal”, or any other type of journal of your choosing.


I launched my first Hormone Horoscope App in 2013. This was a full six years before Apple’s watch finally included its own menstrual cycle tracker. My Hormone Horosocope App was among the first menstrual cycle tracker apps ever created. And, it was–and as of this writing, still is–the only app that delivers a detailed daily summary of how hormones impact your moods, health and behavior.

I hired a two-person app development team from upstate New York to design and code the app, and we worked closely together to painstakingly pave the way, break ground and iron out the kinks of what kind of menstrual cycle tracker app I wanted to create.

In 2015, I released more Hormonology apps with the same team–the Hormone Horoscope Pro App that delivered lengthier, more detailed information about hormonal effects every day of a woman’s cycle and allowed you to track your cycle for months and years. Soon after that came the Female Forecaster App–an app written for male partners of cycling women. All in all, we created six menstrual cycle tracker apps together.

Creating the apps was back-breaking work for my app team. And they were an expensive venture for me personally. But, it was all worth it because I knew these apps would be an effective way to disseminate vital hormone information and teach woman about tracking where they were in their cycle, an important tool for self-knowledge.

I point out all this because I want to underscore my long experience with menstrual cycle tracker apps and how important I felt they were to create.

So, when I say the following, I’m not saying so lightly: If you have a menstrual cycle tracker app that is not one of my Hormonology apps, consider deleting it from your device now. At least until you can confirm with 100% certainty that menstrual cycle tracker app isn’t selling, sharing, using or accessing your personal cycle data and any other information you store in the app.

The privacy problem with menstrual cycle tracker apps

From the beginning, all of my Hormonology apps have been 100% private. There has never been any way for my app team or I to see any information that a user puts in. I can’t access your cycle length, your diary or notes or even the types of emoticons you use in your Cycle Calendar. All information is stored on your own device. That’s why there is a reminder to back-up your data on the app; only you have access to it.

I don’t have any advertising on any of my apps. Never have. Never will. Not only do I find ads a cluttery mess that detracts from the app itself, ads track user habits, which means invading privacy.

Unfortunately, as the menstrual cycle tracker app industry grew, other developers had different goals in mind: They saw apps as a huge money-making opportunity. And they knew that the best way to make the most money wasn’t by selling the apps to users–it was by selling the data  users put into the apps themselves to third parties.

Developers realized they can tap into the now-growing trend to track and understand our cycles. After all, we use our menstrual cycle trackers to monitor virtually every aspect of our lives: our moods, energy, food intake, sex drive, sex frequency, memory, shopping habits, health issues and more. We’re inputting a treasure trove of detailed information. These developers figured out that they can sell this data to anyone–advertisers, corporations, political entities, insurers, you name it–and make themselves and their investors a bundle of cash.

Just how much money can be made? According to this January 8, 2020 Forbes article, “Femtech” (female health technology, which includes menstrual cycle tracker apps) is projected to be “a $50 billion dollar industry by year 2025.” And in 2019 alone, “Femtech received just short of $800 million in funding.”

Alarmed by the potential for abuse, independent consumer advocacy groups have been examining popular apps to uncover what kind of sensitive data they’re selling and to whom. In January 2020, the Norwegian Consumer Council released this report that found 10 popular apps–including two well-known menstrual cycle trackers–were collectively feeding personal information about users to 135 third-party companies.

What’s so bad about your data being sold or shared?

In many countries, there are no laws limiting who these app developers give your personal data to. And there’s no way to ensure that there isn’t any identifying information attached. This leaves the door wide open for all types of abuses that can boomerang on women.

For example, say health insurers buy information from a menstrual cycle tracker app and they discover that women with pelvic pain make four times more frequent visits their doctor than those without pelvic pain. This can impact health insurance premiums and whether a woman diagnosed with pelvic pain can even get insured.

Or, say a political party wants information about women’s moods, thoughts and opinions leading up to an election so they can create advertisements designed to manipulate women into voting the way that this political party wants–or manipulate those from the opposing party into staying home and not voting at all. If they purchase app data, they’re getting access to any personal notes you’ve typed in about how you’re feeling and any opinions you’ve expressed.

These are just hypothetical examples, but since you don’t know who is looking at your data or how much of your personal information they have access to, you certainly don’t know what they’re doing with it or how they’re using it against you.

But, for one real-world example of user data abuse, simply look to Facebook. In 2012, Facebook allowed researchers to access users’ accounts and select which posts nearly 700,000 Facebook users would see in their feeds to deliberately affect their emotions.(1) Their purpose was to examine “emotional contagion”, which is how much someone else’s mood rubs off you on, making you adopt that mood. In the experiment, some Facebook users saw mainly negative posts by others and some Facebook users saw mainly positive posts by others. The researchers found that this manipulation created a small change in mood–those who saw negative posts became more negative about themselves; those who saw positive posts became more positive about themselves. According to an article about this study in The Atlantic, even the researchers recruited to work with the data felt uncomfortable about the sticky ethical issues involved.

Been told sharing your data helps women’s research?

App developers are finding out that many women value their privacy and aren’t too happy to learn that their personal emotional, physical and health information is being sold and shared on the open market. So, these developers have been trying out a new tactic to get you comfortable with the idea: They’re telling you that by letting them sell and share the data from your menstrual cycle tracker app, you’re helping to advance women’s health research.

This is misleading.

As the creator of six menstrual cycle tracker apps and as a professional women’s health journalist for more than 25 years, I can tell you that data collected from these apps is unreliable. This is for several key reasons:

You cannot know how many app users are using the app incorrectly. This can be due to a language barrier (apps are available worldwide, but typically in just one or two languages) or because they simply didn’t understand the instructions. I know this because since 2013, I have received tens of thousands of emails from app users with their feedback. And using an app incorrectly is a common issue.

You cannot know how many app users are inputting inaccurate data. Some users let their app lapse for months at a time, essentially letting it go on auto-pilot, before picking it back up again. Others toy around with the settings to see what happens. Still others could be people who don’t menstruate at all–for example, teenage boys who are just having fun and want to see what all this cycle stuff is about. But, there is no setting that tells the app developer who the app user really is and if they’re inputting correct cycle data.

You cannot know how many app users have medical issues that impact their cycle. Some users could have diagnosed or undiagnosed conditions that impact the data they enter into the app. Imagine trying to rely on data about menstrual cycles when an unknown portion of this data comes from women with health issues that make their cycles longer or shorter, or their periods heavier, lighter or non-existent. On top of all this, lifestyle issues can impact follicular and luteal phase length, such as stress and tobacco and marijuana use.(2,3)

We’ve already seen published research using app data. A 2019 study in the journal Digital Medicine that claims the average cycle length is not 28 days as we’ve all heard, but 29.3 days.(4) The researchers determined this based on more than 600,000 entries from a popular menstrual cycle tracker app. But, how many of these entries were reliable? How many fit the above categories and skewed the data?

Let’s go back to that infamous 2012 Facebook study. That data included nearly 700,000 Facebook users, yet in the founder of PsychCentral, John M. Grohol, Psy.D., concluded that the study was still faulty and unreliable.

So why are app developers giving my data to researchers?

You may have read or heard that app developers aren’t making any money off of sharing your data with researchers. They’re doing it out of the goodness of their heart to advance science. Well, that’s not exactly the entire reason.

When an app company gets included in a study that the media covers, then that app company gets two benefits: They get media coverage they don’t have to pay for, which is free advertising. Plus, they get the credibility that comes with being attached to a “scientific study”. And there are bonus points if the researchers come from a well-known university of health facility.

So, yeah, maybe they’re hoping to advance science. But, they’re also hoping to get more downloads by spreading the word about their product. Make no mistake about that.

But how can researchers do their work if we don’t share?

Researchers have been conducting dependable, trustworthy studies on women’s health and menstrual cycles for decades. And, they have been overseeing studies that include large numbers of women, such as the Nurses’ Health Study and Study of Women’s Health Across the Nation (SWAN) study.

The benefits of these kinds of studies are that the researchers know who they’re getting information from because they meet them and survey them, they track these participants over time to ensure they’re getting accurate information and, I can’t stress this enough, the participants know they are part of a study. There is informed consent.

If we want more research examining women’s health, hormones and cycles, we need to support the scientists, facilities and organizations that conduct it. For starters, you can sign up to participate in studies. And since women’s health research is traditionally underfunded compared to men’s research, we can help fund it ourselves by leaving a portion of our estate to universities, healthcare facilities or organizations that support women’s health research. Or we can take out a life insurance policy and appoint a university, healthcare facility or organization as our beneficiary.

I actually do believe that there is, in fact, a place for menstrual cycle tracker apps and other fem-tech in women’s health research. But, I believe the participants need to be fully aware they’re participating in a study and what the study is. Right now, most app users are simply agreeing to a blanket legal jargon-filled privacy-waiving statement when they download their app. Additionally, participants need to be fully vetted so it’s certain they’re using the apps correctly, they fit the appropriate demographics, there are no health or lifestyle issues that complicate or nullify results, etc., so that the study can be reliable.

There are better ways to obtain accurate information about women’s cycles for research than casting a wide net and obtaining it blindly from menstrual cycle apps. And I don’t believe that guilting women into believing it’s their duty to give up their privacy to be able to track their menstrual cycles in order to advance cycle research is in their best interest.

But, does privacy really matter anyway?

When an app tracks your emotional states, physical changes and health issues, and you can type personal notes into it, it’s more than just an app. This is your diary. This is your healthcare record. This is a record of your life.

Would you give these personal items to strangers you saw on the street? Would you hand them over to advertisers? Would you let health insurers who decide rate premiums and coverage take a peek? Would you give them to researchers who could use them to manipulate your moods?

What if someone told you that they’ll remove your name and other identifying information linking it back to you? Would you simply trust that they’d do it?

What if someone told you that they’ll only sell or share these personal items with the most trustworthy and upstanding citizens they’ve ever met? Could you really believe that they would know who to trust with your personal records?

What if that person also told you that they’ll never lose these records and they’ll never get stolen while they’re in their care? Could you believe this?

If the answer is no to any of these questions, then you understand why privacy matters.

Get it in writing–but still be cautious

I’m saddened and disappointed to see that many of my peers in the menstrual cycle research community are vigorously encouraging women to share personal data that includes your emotional states, day-to-day behaviors and health.

Unfortunately, some who support this push to give up your privacy are benefiting from this app data themselves: They’re accepting advertising money from menstrual cycle tracker apps, are spokespeople for these apps or are getting this app data to use for their own studies, which in turn benefits their careers. And some of these ardent supporters have no background in fem-tech other than using apps themselves.

As an actual menstrual cycle track app creator and a longtime women’s health journalist, I’m telling you that you never have to give up your privacy to track your menstrual cycle. 

That’s why if you have concerns about privacy, I’m encouraging you to look for the privacy statement for your menstrual cycle tracker app–and if it doesn’t assure 100% privacy, delete it now. (Here is my Hormonology privacy statement.)

I think I’ve made it pretty clear that I would never sell or share your data. But, please keep in mind that privacy policies for other apps can change at any time, so keep checking them.

Switch to a paper menstrual cycle tracker journal

I was at the forefront of menstrual cycle tracker apps. Now I’m encouraging you to go old-school: Keep a paper menstrual cycle journal. Use a plain notebook. Use a Bullet Journal. Or use my Hormonology Menstrual Cycle Tracker Journal, which includes more than 70 categories to track and can be customized to include even more. I created this paperback journal specifically to help ensure you have 100% privacy while being able to comprehensively track every facet of your cycle.

Tracking your menstrual cycle is an important part of understanding your hormonal effects and treating cycle-related issues. Keeping your personal cycle information and health details private is just as important.

(1) Adam D. I. Kramer, Jamie E. Guillory, Jeffrey T. Hancock, “Experimental evidence of massive-scale emotional contagion through social networks,” PNAS, 111 (2014): 8788-8790
Sara Lammert, et al., “Menstrual Cycle in Women Who Co-use Marijuana and Tobacco,” Journal of Addiction Medicine, 12 (2018): 207-211
(3) Jinju Bae, Susan Park, and Jin-Won Kwon, “Factors associated with menstrual cycle irregularity and menopause,” BMC Women’s Health, 18 (2018): 36
(4) Jonathan R. Bull, et al., “Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles,” Digital Medicine, published online August 27, 2019



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