Daysy Fertility Tracker

In stock

Discover your menstrual cycle – and your fertility!

Daysy empowers you to understand your menstrual cycle.

The DaysyDay app is free on iOS and Android smartphones

Understand your fertility window to make better fertility choices.

Two year manufacturers warranty.


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Daysy Fertility Tracker
  • Buy 2 for £269.00 each and save 10%

How to use Daysy fertility monitor

Discover your menstrual cycle – and your fertility!


Daysy empowers you to understand your menstrual cycle.


What Daysy is:


Daysy is a medical device and lifestyle fertility tracker. Daysy is to be used to facilitate conception and track your cycle. Daysy allows every woman who wants a health-conscious lifestyle to monitor her individual monthly cycle and determine her fertile and infertile days in natural harmony with her body.


What Daysy does:

Daysy is an effective and science-based method which allows you to easily, reliably, and precisely differentiate between your fertile and infertile phases, based on the precise measurement of your basal body temperature. 

Fertility Chart

How to use Daysy:


Every morning, upon waking, you measure your basal body temperature under your tongue for just 60 seconds and enter menstruation if necessary. Daysy immediately analyzes your cycle data and shows you if you are in your fertile window or not.

Why you can rely on Daysy:

Due to an intelligent algorithm based on scientific evidence, decades of experience, and well-engineered technology, Daysy provides the highest quality, reliability, and precision in fertility tracking. 


How Daysy informs you:

Daysy shows you your fertility status as either a red or a green light. This way, you always know when you are in your fertile window and when you are not. This technology-based temperature method, used by Daysy, is one of the most reliable methods in the world for fertility tracking.


Daysy has her own app:

DaysyView app

The DaysyDay app makes Daysy compatible with smartphones and thus offers new options for digitally expanding your knowledge of your unique menstrual cycle and body. DaysyDay also gives you the ability to share your information with your partner, doctor, or our expert team.

In addition to displaying your individual cycle calendar and temperature curve, DaysyDay shows you a range of statistics about your menstrual cycle. You will see a prognosis for your fertility status over the coming weeks so you can plan ahead. 


Daysy highlights:

  • Daysy is perfectly simple and straightforward.
    Take your basal body temperature in just about 60 seconds, enter menstruation when necessary, and Daysy will indicate the days when you’re fertile and the days when you’re not.

  • Daysy is reliable and precise.
    With well-engineered technology and an intelligent algorithm, Daysy guarantees top quality and reliability – in a completely natural way. Be in touch with your body.

  • Daysy has its own app.
    With "DaysyDay," you can view the details of your cycle and can share these with your partner, doctor, and our team of experts.

87% would recommend Daysy


#LoveYourBody - Daysy is all natural and empowers you to live in harmony with your body.



General questions about Daysy


I sleep with my mouth open. Can I still use Daysy?

Yes. If you sleep with your mouth open, just close it once and swallow before you measure. The measurement is finished when the temperature has reached its final value and you hear a soft beep beep from Daysy. Daysy may take a couple of seconds longer to measure for those users who sleep with their mouths open. Please be sure not to open your mouth while measuring.


If I upgrade from Daysy 1.0 to Daysy 2.0, will my data automatically transfer from the app to my new Daysy 2.0?

No, in order to transfer your data from your Daysy 1.0 to your new Daysy 2.0 you will need to send your data file to customer support. Customer support will transfer your data file to your new Daysy 2.0 before it ships out. Please get in touch with customer support prior to purchasing a Daysy 2.0 if you’d like to have your data transferred.


How do I store Daysy at night?

To avoid damage, please do not place Daysy under your pillow. Keep Daysy in a safe place within easy reach.


Can I share Daysy with a friend?

No, Daysy is your individual fertility tracker with your individual data.


How does Daysy work?

Daysy is programmed with a complex algorithm which evaluates your cycle by tracking your morning temperature (taken under the tongue) and knowing when you have your period. Daysy will then show you right away if you are currently fertile or not.


Does Daysy come with all the necessary accessories?

Yes, your initial Daysy order includes everything you need.


Will my displayed fertility status be correct while I am taking medication?

That depends on whether the medication influences your body temperature or your cycle. In general, you should skip measurements while you are taking such medication. If you have doubts, contact your doctor or our customer service team.


Does illness reduce the reliability of the device?

In general, you should skip measurements during illness and while you are taking medication that can have an influence on your body temperature or cycle. If you have doubts, contact your doctor or our customer service team.


What do I do when I stop using Daysy?

Daysy 1.0: Remove the battery and store Daysy in a dry location in its original packaging, if available. You can find more information in the instruction manual.

Daysy 2.0: Please store it in a cool, dry location. While stored, please remember to charge your Daysy once every 2-3 months to maintain the internal battery.


How long until Daysy knows my personal cycle?

The first 2-4 cycles of use are considered Daysy's learning phase. Over the course of her learning phase, Daysy will come to understand your cycle and begin narrowing down your fertile window. Daysy remains quite cautious and conservative during this time, which is why Daysy is accurate starting the very first day.


What happens if I miss a measurement?

Based on its recorded data, Daysy can compensate for the occasional missed reading. We still recommend you measure as regularly as possible so that your fertile phase can be narrowed down as precisely as possible. If you have to skip measurements due to illness, Daysy will get back on track once you start again.


When can I start to rely on Daysy's results?

You can rely on Daysy's results starting the very first day of use. In the beginning, you will see more yellow and red days because Daysy is still learning your unique cycle. You will see more green days as Daysy comes to understand your cycle and can narrow down your fertile window. The more regularly you measure, the better.


Do alcohol or smoking influence the measurement?

Smoking should not influence the result. Alcohol, if consumed excessively or when your body is not used to it, does influence basal body temperature. If you can feel that you were drinking yesterday, you should skip your reading in the morning. If you feel just fine and have no headache or other symptoms of alcohol consumption, you are fine to temp as usual.


How long does my order take to arrive?

3-5 days. For more information please check our general terms and conditions.


Does Daysy come with a warranty?

Daysy comes with a 2-year warranty. You can find all the relevant information in the general terms and conditions.


How often should I take my temperature?

Ideally, you measure daily. The fewer measurements you miss, the better.


How does Daysy react to increased temperatures, e.g. fever?

A fever is when your body temperature reaches at least 38°C (100.4°F) degrees - if this is the case, you will most likely feel ill and you will notice that your temperature curve is unusually high (see example curve). The DaysyDay app will alert you that your temperature is high and recommend you temp with a standard medical thermometer. Temperatures above 37.8°C (100.4°F) or below 35°C (95°F) degrees are automatically excluded from the algorithm and will not be used for your fertility calculations.


What do Daysy´s lights mean?

Red = fertile / possibly fertile (On red days you can plan for a pregnancy.)

Red flashing = predicted day of ovulation

Green = infertile days (You are not fertile on green days.)

Yellow = learning phase/cycle fluctuation (Yellow days should be considered as red days.)

Red, green, yellow (blinking) = possible pregnancy

Tutorial for Daysy 1.0

Tutorial for Daysy 2.0


Should I keep measuring after a vaccination?

First things first: If you feel that there is something not right, you feel sick, or you have pain, never hesitate to consult your doctor! Most people tolerate vaccinations without any problems. Sometimes, however, vaccination reactions occur: These are almost always harmless after-effects of vaccinations, which in the vast majority of cases pass very quickly. Some vaccinated people react with a slight fever (below 39°C / 102°F), aching limbs or faintness. The fever can occur only a few hours after vaccination and last up to 3 days. Such vaccination reactions are usually completely harmless and no cause for concern. As a rule of thumb: If you wake up in the morning after the vaccination and feel different than usual, for example sick or overtired, then interrupt the measurements until you feel better again.



How do I use Daysy?


What is the best way to measure?

Use Daysy in the morning right after waking up, before getting up and becoming active. Measure below your tongue, with your mouth closed, and keep the device steady while it is measuring. We do recommend that you sleep 3-4 hours before measuring.

Tutorial for Daysy 1.0

Tutorial for Daysy 2.0


I want to start using Daysy after a pregnancy. What do I do?

Please contact your customer service for guidance.


I missed a couple of measurements. What should I do?

One or two skipped measurements are not a problem; Daysy will simply use your earlier data to calculate your fertility. Multiple missing values per cycle will lead to a higher number of red or yellow days.


How can I check my fertility status later in the day?

Simply press the activation button and your fertility status will be displayed.


Can I measure multiple times per day?

No. Daysy will only record the first measurement of the day.


When can I start using Daysy?

You can immediately start with the measurements. If you were using hormonal birth control before, stop using it before you begin measuring. The first bleeding after coming off hormonal birth control is a withdrawal bleeding and must not be entered as your period. If you are menstruating when starting with Daysy and you cannot enter all days, do not enter the current menstruation, but the next one. The first day of menstruation is important because it marks the beginning of your cycle.


Where do I measure?

Below the tongue in the pocket next to your frenulum and with your mouth closed. It is best to measure on the same side each morning if comfortable.


I am slowly approaching menopause. Can I still use Daysy?

Yes, you can. Daysy is also reliable during the transition to menopause. If your ovulation is delayed or doesn't occur, Daysy will display more red and yellow days. Using Daysy will allow you to directly observe the changes that are happening to your cycle.


Can I use Daysy during breastfeeding?

Yes, Daysy can be used while breastfeeding. You should not start measuring until 6 weeks after birth. Since there is no way to predict the first ovulation after birth, Daysy will stay yellow until the first menstruation is entered postpartum. Once you enter your first period, Daysy will display fewer red and yellow days in the following 2-4 cycles as Daysy gets to know your unique cycle rhythm.


Is there something I have to be aware of when traveling to a different time zone?

Daysy 1.0: If you traveled overnight, skip the first measurement after your arrival and continue to measure regularly the next day after resuming a normal sleep cycle. Do the same thing when you return home from traveling.

Daysy 2.0: When traveling with your Daysy, it is important to set the time on your Daysy to the local time before resuming your temperature readings. Set your mobile phone to the local time zone (many phones will do this automatically) and synchronize your Daysy with DaysyView/DaysyDay to set the time on Daysy. Take your temperature and resume use as normal the next morning.


I had a sleepless night. Can I still rely on Daysy?

Yes, you can always rely on Daysy. If you have to skip a measurement after a sleepless night, Daysy will still reliably display your fertility status. Depending on where you are in your cycle, Daysy will react accordingly.


How long does it take to measure?

It will take approximately 60 seconds to measure.


How do I switch Daysy off?

Daysy automatically switches off after 60 seconds.


Is it possible to delete individual measurements?

No. Daysy only records the first daily measurement. If you have concerns about a reading, please contact our customer service team.


Do I have to measure at the same time every day?

No. What is important is that you measure immediately upon waking after getting 3-4 consecutive hours of sleep, before getting up and being active.


How do I know when I am fertile?

When Daysy displays a red light, it means that you are fertile. You can check your status anytime by activating Daysy.


My sleeping intervals are irregular (rotating work shifts, getting up at night, sleeping in on the weekend, etc).: Is Daysy also suited for me?

Yes. Daysy has been designed for women like you. Simply take your temperature when you wake up.

Daysy 1.0: Daysy only registers one measurement after 18 hours have passed since your last reading.

Daysy 2.0: Daysy only registers one measurement per day. If the next day has not yet started, a tone (beep-beep) will sound.


I have to get up frequently during the night because I have a baby. Can I use Daysy?

Yes, but for the optimal use of Daysy we recommend that you sleep at least 3 consecutive hours before measuring.. If you don't get that during certain nights, there is no reason for concern. Daysy can handle skipped measurements from time to time.


Should I also use Daysy during my period?

Yes, please take your temperature throughout your entire menstrual cycle. However, on some days you should refrain from taking a measurement: for example, after excessive alcohol consumption, when you are ill (fever) or when you are feeling very bad.


How do I enter or edit menstruation?

Turn on Daysy. Press the activation button until the violet light lights up without flashing and you hear a "beep". Confirm you are menstruating for each day of active bleeding and flow for a minimum of three consecutive days. You can change menstruation data for the same day by turning Daysy on and pressing and holding the activation button until the purple/blue light is no longer solidly lit.

Tutorial for Daysy 1.0

Tutorial for Daysy 2.0



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