Type “period tracker app” into your phone app store, and you can scroll through more than 40 options, both free and for purchase.

There are ample reasons women use them – to track their menstrual cycles for the convenience of knowing when they’ll likely start and stop, to track ovulation to try to prevent pregnancy or to support conception (especially in their first year of trying to get pregnant), to identify patterns of frustrating symptoms and more.

Depending on which one you choose, your period tracker app can process data you input over time, like period start and stop times. That will allow it to start predicting future start and stop times, along with fertility windows, too. Certain apps can also be programmed to send you reminders about your period and ovulation times. If you are using a period tracking app or are considering one, know that privacy concerns have been raised. Experts advise you to research the issue using trusted sources of information.

Dr. Alyse Kelly-Jones is wearing a white lab coat and smiling.
Dr. Alyse Kelly-Jones
Choosing the best period tracker app for you should be goal-based. Look at the reviews and try to write down your top five goals for using an app, said Dr. Alyse Kelly-Jones, the founding provider of Novant Health Women’s Sexual Health & Wellness in Charlotte. “Try to find an app that fits those goals whether you have to pay for it or not.”

Need a little guidance? Here are seven things to know about using a period tracker app.

Information stored in period tracker apps can help you manage mood fluctuations.

“It’s important for women to realize they do have dramatic hormonal fluctuations during their cycle when they’re not on birth control,” Kelly-Jones said. “Even women with IUDs can have these changes because the ovary still works in the background of an IUD.”

Rather than assuming there’s something wrong with your moods, you could start to notice a pattern in the symptoms you track in your app that could coincide with rises and falls in hormones over each month.

“If you know it’s that time of your cycle where you get mood issues, or you get bloated, then that’s the time to do the things that are natural that can help,” said Kelly-Jones. Those strategies can include exercising and eating high-quality foods.

They can prompt you to become more aware of the physical signs that you’re ovulating.

During ovulation, Kelly-Jones said, “There’s actually a change in your cervical mucus. Basically, that turns into a change in your vaginal discharge. So you go from having something you don’t even notice to having this thicker, stickier stuff, and that’s a sign you’re ovulating.”

Since a lot of apps indicate when you’re ovulating, you can be reminded to pay more attention to your body’s physical cues.

Apps can help you better understand ebbs and flows in sex drive.

Libido can be heightened or lessened depending on where women are in their menstrual cycles. “Mother nature gave us a testosterone peak right before we ovulate,” Kelly-Jones said. “So women often have more sexual desire for a partner when they’re most likely to conceive.”

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Period tracker apps can help ease anxiety for women trying to conceive.

Women coming off birth control pills may notice their period doesn’t come right on time, the way it may have during years of hormonal contraception usage. But if they're paying attention, Kelly-Jones said, and they know their cervical mucus changes around day 14 (for example), they can acknowledge that they’re ovulating. That’s a good sign that the woman is making an egg, meaning that part of her reproductive process is working well.

You can’t rely on period tracker apps to prevent pregnancy.

No matter how much data you give them, period tracker apps are not always accurate. Many offer a more data-driven way to follow the rhythm method, a type of natural family planning that relies on menstrual history to predict ovulation and to indicate windows of time where conception is most likely.

But, Kelly-Jones said: “You can ovulate earlier than you think, your egg can hang around longer, the sperm can hang around longer.” You can’t expect an app to know that information.

Period tracker apps can help you store useful information for doctor visits – like the date of your last menstrual period.

“I’d consider that almost like a vital sign,” Kelly-Jones said. “Blood pressure, height, weight, when was your last menstrual period.”

For younger women, doctors need to be aware of pregnancy risk, especially when prescribing medications or advising procedural or surgical care. That applies to women in their 40s as well, plus the additional question of whether they are beginning to transition toward menopause (when their period stops) and whether more information about upcoming physical changes would be helpful.

If you do start using a period tracker app, be diligent about entering your information.

“The app basically learns who you are,” Kelly-Jones said. “The more data you put in there, the more it’s going to figure out how you actually work.”