Things you need to know about LH tests!

Do you have irregular cycles? Or have you just quit the pill? You might want to combine measuring your temperature with LH tests that are now from our webshop:


What is LH and why test for it?

LH stands for Luteinizing Hormone and appears for about 48 hours and is shortly followed by ovulation. You can read more here if you are interested in the science of fertility.

If you have irregular cycles then we highly recommend testing for LH. If you have recently been on hormonal contraception, it is likely that your cycle will be out of balance and irregular for up to a year. This is very individual and is taken into account by NaturalCycles’ clever algorithm, which will be even more cautious if this is the case.

It is not necessary to test LH if you do not want to, but it is a powerful supplement to the basal body temperature to indicate when ovulation has occurred. Temperature measurements have day-to-day fluctuations, which can make it challenging to identify the exact ovulation day quickly – the more data entered the easier it becomes! However, positive LH tests can help speed things up and give you more green days quicker.


2. How do I know when to test for LH?

As a woman’s LH surge happens just before ovulation, NaturalCycles will recommend that you to check LH levels a couple of days before the expected ovulation. How far in advance you need to start testing depends on how regular your cycles are.

Depending on whether you use the website or the app, the LH reminder looks a bit different. On the website, you can hover over the calendar with your mouse and you’ll see a reminder in red, for instance on the day before predicted ovulation. On both the website and the app, you’ll see “LH” with an arrow pointing at the day of the week that you should measure on, and you will also see that the the LH field will be pre-opened on the ‘add data’ window.  Additionally, on the app you will see a “Today!” notification next to the LH entry field for the day that you should test on.




Or in the app:




Please get in touch if you have questions about LH or anything else!
Have a nice thursday!

Lots of Love

NaturalCycles Team


Red day Facts

A common question we often get from new users is: “Why do I have so many red days? Am I always fertile?”

The answer is of course, no! No woman is fertile for more than 6 days per cycle. The fertile window starts 5 days before ovulation (because sperm survival is ~ 5days) and ends after ovulation.

Before NaturalCycles can pinpoint your 6 day fertile window it has to first get to know what is normal for you. After all, every women is unique.



So what else can influence your number of green days?

Quitting the pill

Women who quit the pill (or other hormonal contraceptives) and switch to NaturalCycles question the number of red days they get at the start. Why? This is because hormonal contraceptives disturb a woman’s normal menstrual cycle, thus leaving women with irregular cycles until the synthetic hormones leave their bodies, and this can take several months. NaturalCycles takes this into account, giving more red days until things start to get back to normal.

Measuring and fluctuations

Another important factor to consider is, how and when you measure your temperature. We advise you to avoid measuring when you are sick, feeling hangover or if you wake up much later/earlier than usual. You can read more about measuring and basal thermometer here


Your temperature varies from day to day, but more considerable fluctuations can occur during ill or hungover days. These fluctuations in temperature can resemble ovulation or otherwise, which means NaturalCycles will give you a red ‘fertile’ day just to be safe. If you think this has happened to you then please get in touch at and we can take a look at your data and remove the anomaly that might be tainting how your cycles look.

So with this in mind, please don’t loose hope as green days are just around the corner. The more data you enter, the better NaturalCycles can pinpoint your fertile window, giving you green days in return. Have a look at this happy cycle:


To find out your fertile window and ovulation day faster, we also recommend taking an LH-test. A surge in LH hormones occur two days before ovulation and marks your most fertile days. NaturalCycles let’s you know when to check your LH levels, which also depends on how regular your cycles are. Have a look below to see what our reminders look like:


















So to sum-up – don’t worry, because green days are ahead! Just make sure you keep measuring everyday!


keep calm naturalcycles