Daysy is a fertility tracker designed for people who want to conceive. It uses a proprietary algorithm and basal body temperature to calculate the daily menstrual cycle in real time.

Many people use it for natural family planning. But some people are interested in Daysy for its cycle tracking capabilities and use as an alternative to hormonal birth control or as a supplement to family planning tools.

Here’s what you need to know if you’re considering Daysy.

Daysy is a small medical device that functions as a fertility tracker. It uses your daily temperature to track when you’re most fertile or most likely to conceive during your cycle.

The small device takes your temperature each day and pairs with a free app, where you can view information related to your fertility.

People with a uterus and ovaries can use Daysy. In general, Daysy can be a good resource for people wanting to learn more about their fertility.

Knowing when you’re fertile may help increase your chances of conceiving if that’s your goal.

While some people like using Daysy’s fertility tracking features as part of their natural birth control method, it’s designed for people who are trying to conceive.

Daysy works by increasing your fertility awareness, so you can make family planning decisions accordingly. During your fertile window, you’re more likely to conceive than on the days outside your fertile window.

Daysy uses your basal body temperature and menstruation data to calculate when you’re more likely to conceive and when you’re less likely to conceive. Daysy takes your temperature using a precise sensor, stores your data, and calculates your fertility status.

Daysy signals the fertility status using the lights on the device:

Daysy is simple to use, but it must be used every day. Your results will be most accurate with consistent daily measurements.

You’ll use Daysy first thing in the morning before you get out of bed. It’s recommended to get at least 3 to 4 hours of sleep before using Daysy.

Part of using Daysy involves recording your menstruation. When you’re on your period, press the activation button until a violet light appears and the device beeps once.

In the beginning, Daysy will be in the learning phase. Expect to see a lot of yellow lights as Daysy’s algorithm learns more about your fertility. The more you use Daysy, the more it learns about you.

Daysy is available to purchase on the company’s website, usa.Daysy.me.

It’s also available on:

Daysy is rated highly on Trustpilot and Amazon. Customer reviews praise the company for good customer service and warranty. Many customers write about their positive experiences using Daysy to prevent or plan a pregnancy.

“This a great alternative if you [are] trying to avoid hormonal birth control,” writes Amazon user Stori Evans. “I am still learning about this device, but after a while, you get the hang of it. It has also helped me learn more about my body.”

Other reviews aren’t so positive, saying the company has faulty products, glitches in the app, and high prices. Users report experiencing technical difficulties with the device and app.

“It never syncs properly with the app. You have to continue doing it over and over [until] it finally works. When I input information, half the time it doesn’t save. It takes about 2 minutes for it to take your temperature,” explains a reviewer on TrustPilot.

A common complaint among users is the high frequency of yellow days, which indicate potentially fertile days or that Daysy is still learning. Some reviewers mention they still became pregnant despite using the device to prevent unwanted pregnancy. That being said, the device is not marketed for pregnancy prevention.

There are no physical side effects when using Daysy to track cycles. It’s as safe as taking your temperature with a regular thermometer. It’s also registered with the Food and Drug Administration (FDA).

Fertility and family planning are complex, so there’s a wide variety of birth control methods out there. The best option for you depends on your goals, and there’s a possibility that Daysy may not be a fit for you. However, there are other natural birth control methods to consider.

A popular alternative to Daysy is simply tracking your cycle and taking your temperature yourself. Tracking and understanding the rise and fall of your basal body temperature throughout your cycle can help you predict the days you’re fertile.

Daysy does this for you, but doing it yourself is an option if you have trouble with the app or want a budget-friendly option.

If the fertility awareness associated with Daysy is what intrigues you, consider the rhythm method. This involves tracking your menstrual cycle and using the data to predict future cycles and gain a better awareness of your body.

Additionally, Phexxi is a newer nonhormonal birth control gel, available by prescription, that’s placed inside the vagina just before penis-in-vagina sex to reduce the risk of pregnancy. It works by preventing semen from changing the pH of the vagina.

Natural Cycles, or NC, is an app designed for birth control and fertility awareness.

Using the NC thermometer and the app’s algorithm, it uses basal body temperature and menstrual cycle to help calculate a user’s fertility status.

It was first cleared for use as a contraceptive device in 2018 by the Food and Drug Administration (FDA).

Getting started with Daysy is simple.

You can start by ordering your Daysy tracker and downloading the app. Before the first use, you’ll need to charge the device. After that, you’ll need to charge it using the USB cable every 1 to 2 months.

Daysy comes with everything you need, so you don’t need to purchase anything else.

You can talk to a doctor at any point for advice or to work with you if you’re considering doing natural family planning. Consult your doctor if you’re taking any medications that affect your body temperature. This can interfere with the effectiveness of Daysy.

If you’re currently using other forms of birth control given to you by your doctor, check if Daysy is compatible with your existing method. Daysy should not be used while on hormonal birth control.

Daysy claims to be 99.4 percent accurate. This was confirmed by a study funded by the company. In 2018, unaffiliated researchers found that Daysy wasn’t as accurate as the company claims, and the company’s article was retracted shortly after in 2018.

A new study funded by the company in 2020 also found the device to be 99.4 accurate in distinguishing fertile days from infertile days, and still stands.

Daysy doesn’t accept health insurance as a form of payment, but you may be able to get a portion of the cost reimbursed by your health insurance plan.

It’s also eligible for health savings accounts (HSAs) and flexible spending accounts (FSAs).

Daysy is pricey, but it’s a one-time expense. Over time, it may be less expensive than ovulation test strips or other tracking devices.

If you’re looking for a natural family planning, it may be worth the money to you, but this is subjective.

By comparison, if you have health insurance or depending on where you live, the cost of birth control medication may be covered completely, while IUDs can be considered cost effective given that they last for years and are very effective at preventing pregnancy.

Yes, you can still get pregnant on your period and outside of ovulation. You can also still get pregnant on birth control, though this is rare, and in other scenarios such as while breastfeeding.

For those looking for ways to track their menstrual cycle and fertility, Daysy is one option on the market. However, if you’re not trying to conceive, we don’t recommend it as an alternative to hormonal contraception.

There are many other birth control methods, from conventional condoms to other natural or nonhormonal birth control methods.

Lacey Muinos is a health, wellness, and beauty writer based in Southern California. She holds a BA in English. Her work has appeared in digital publications like Livestrong, Verywell, Business Insider, Eat This Not That, and others. When she’s not writing, Lacey is likely pursuing her other interests: skin care, plant-based cooking, Pilates, and traveling. You can keep up with her by visiting her website or her blog.

Last medically reviewed on August 29, 2022

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