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Frequently Asked Questions

Read up on the questions we get asked the most.

To use the app you will need a basal thermometer. Basal thermometers are more sensitive than regular fever thermometers as they show two decimals (e.g. 36.72°C / 98.11°F). The amount your temperature changes is quite small, so to get the most out of Natural Cycles and receive more green days you will need the correct thermometer. The good news is that you get one included when you sign up for our “annual subscription”.

The Natural Cycles algorithm adapts to your unique cycle pattern by learning over time as you add more data. When you start using Natural Cycles, it can take some time to get to know your unique cycle, resulting in an increased number of red days during your first few cycles. The increase in the number of red days is to ensure that the app is effective, but once it has detected your ovulation you are likely to receive more green days. After three months, most women will see an increase in green days, depending on the regularity of your cycle and the consistent input of temperature data.

Your temperature will deviate if you feel sick, hungover, have slept more or less (±2 hours) than usual or are traveling across different time zones or climates. Under these circumstances do not measure your temperature that day – then tap ‘Skip today’ – or mark the entry as a ‘Deviating temperature’ in the Add Data view. This way the measurement will not be used in the algorithm’s calculation. The app will still work effectively, but you might get a few more red days. Please read the User Manual thoroughly as this contains all the information you will need to use Natural Cycles effectively.

The number of red days varies Cycler to Cycler as every woman is different so there is no set number of guaranteed red days. It depends on the regularity of your menstrual cycle and how regularly you input data into the app, as well as having a steady temperature. Have patience and give the algorithm time to learn about your body, after three months you should see the number of red days decrease. You and your partner should be comfortable with abstaining from sex or using protection on red days to prevent a pregnancy.

It depends on the type of contraception you are using. If you are using NON-hormonal contraception (condoms, copper IUD etc.), you can get started right away. Hormonal contraception affects your cycle and temperature, so you cannot start using Natural Cycles until you have come off it. You will have to wait approx. a week to get started (read more on Cyclerpedia). After coming off hormonal contraception cycle irregularities are quite common, but you should speak to your gynecologist if you have any concerns.

Natural Cycles may be suitable for women who are looking for an effective,* natural method of birth control and have a lifestyle that enables them to take their temperature first thing most mornings. It is very important that women who want to use Natural Cycles feel comfortable using protection (such as condoms) or abstaining from sex on red days. Using Natural Cycles does require a level of commitment, so the better it suits your lifestyle, the more you will get out of it.

*Natural Cycles is 93% effective with typical use. This means that in a year of use, an average of 7 women out of 100 will get pregnant while using Natural Cycles.

If you have irregular menstrual cycles (i.e. cycles lasting fewer than 21 days or greater than 35 days in length), Natural Cycles may be a less suitable choice of birth control for you. This also applies to users with fluctuating temperatures as predicting fertility is more difficult under these circumstances. Natural Cycles can still be used if you have irregular cycles or an overly varying temperature, but it’s important to remember that you will likely experience a higher number of red days. With this in mind, please consider that you may be less satisfied with Natural Cycles as a means of birth control.

Once you have ordered your thermometer you can expect the following shipping times:

Up to six days for Sweden and the UK. Up to 11 days for the rest of Europe and the US (except Alaska and Hawaii). Up to 22 days for Brazil. Up to 30 days for the rest of the world.

You can order your thermometer in Celsius or Fahrenheit.

We ship thermometers all around the world except to the countries of Mexico, Argentina, Colombia, South Africa, Saudi Arabia, United Arab Emirates, and Chile. You can, however, get your own two decimal certified thermometer and use it in conjunction with the Natural Cycles app.

It’s important to note that Prevent Mode is only approved for use in Europe and the U.S. residents of other countries should use Natural Cycles for planning a pregnancy only.

The effectiveness of Natural Cycles is supported by clinical evidence, which shows a typical use effectiveness rate of 93%. Typical use effectiveness takes into account all possible reasons for becoming pregnant while using the app: from having unprotected sex on a red day to the app wrongly attributing a green day or the chosen method of birth control on a red day having failed.

It is important to note that the effectiveness of Natural Cycles relies on you and your partner using protection (e.g. condoms) or abstaining from sex on red days.

Before you get started, read the User Manual thoroughly as this contains all the information you will need to use Natural Cycles effectively.

Natural Cycles is an app you can download from the App Store or on Google Play. You can start using the app by purchasing a “Monthly or Annual Subscription”. The annual subscription includes a two decimal basal thermometer, which you will need to be able to use Natural Cycles. A basal thermometer is more sensitive than a regular fever thermometer.

Both subscriptions will renew automatically unless cancelled. You can cancel, renew or change payment type at any stage in your “Profile” within the app. If you have purchased via in-app purchases go to your iTunes settings. Please note that with the “annual subscription” payment and you will be charged in full for 12 months of access to Natural Cycles.

Before you get started, read the Instructions for Use thoroughly as this contains all the information you will need to use Natural Cycles effectively.

During your menstrual cycle your temperature rises and falls slightly which is due to the change in your body’s hormone levels. The Natural Cycles algorithm analyzes your temperature (and optional LH test results) and also takes into account other factors like sperm survival, temperature fluctuations, and cycle irregularities to identify ovulation and thereby calculate your red and green days.

Natural Cycles goes beyond just birth control. Our “Plan a Pregnancy” mode can support you in your journey to become pregnant by letting you know the days that you are fertile. Find out about the “Plan a Pregnancy” mode here.

Our CE marking and FDA clearance have been granted based on mandatory clinical data that demonstrates that the effectiveness rate of Natural Cycles is 93% with typical use. This means that Natural Cycles is the first app that has been assessed and deemed effective enough in preventing pregnancy to be categorized as a method of birth control in Europe and the US.

Natural Cycles works by analyzing your basal body temperature measurements. That’s why it is important to measure with a two decimal basal thermometer, after you have slept enough (at least 4 hours) and before getting up and out of bed. You place it under your tongue, as far back as possible and press the button to turn it on. Once it beeps, enter your measured data into the app. 

We recommend that you measure your temperature at least five out of seven days in the week. The app will still work effectively if you forget to measure, but will give you more red days.

The number of green days increases as the algorithm gets to know each woman’s individual cycle pattern. Every woman is different so there is no precise number of green days you will receive. However, the more consistent your data input and the more regular your cycle, the more you will get out of the app. You and your partner should be comfortable with using protection like a condom or abstaining from sex on red days to prevent a pregnancy.

Natural Cycles does not protect against Sexually Transmitted Infections (STIs). Please do keep in mind that the only method of birth control that protects against STIs is the male and female condom. Should you have reason for concern, be sure to use them at all times.

Natural Cycles is an effective*, natural method of birth control and is the only CE marked app intended to be used as birth control and is cleared by the US FDA. It is powered by a smart algorithm that can determine a woman’s daily fertility using basal body temperature. Unlike other fertility awareness methods, Natural Cycles uses only objective data and minimizes human error as the app does all of the calculations and interpretations for the user.

*Natural Cycles is 93% effective with typical use. This means that in a year of use, an average of 7 women out of 100 will get pregnant while using Natural Cycles.

We offer a free demo mode so you can see if the app is right for you before committing to a subscription.

There are two subscription options: either an annual and monthly subscription. Click here for pricing.

Our ovulation prediction algorithm plays an important part in detecting your fertile days. In the graph view you can see your predicted ovulation window – this also shows when the algorithm is waiting to confirm your ovulation and once it has been confirmed. Your predicted ovulation is visible in the Today and Calendar views as well. If the algorithm doesn’t detect your ovulation, you may have had an anovulatory cycle. This means you did not ovulate this cycle. We will let you know if this happens by sending you a message in the app.