Determine your ovulation with the basal body temperature

The progression of the basal body temperature during your menstrual cycle provides information about your fertility. The progression of the basal body temperature during your menstrual cycle provides information about your fertility. This is because around ovulation, the body's core temperature rises (and with it the lowest value of the body's core temperature, the "basal body temperature"). Because women are only fertile around ovulation, this rise is an important fertility indicator. On this page you can learn more about what basal body temperature is and how it can help you determine your ovulation.

What is basal body temperature?

Shortly after ovulation, your body temperature regularly increases by around 0.2 degrees compared to the first half of the cycle. The fact that this works so reliably is due to the hormone progesterone, which is increasingly released after ovulation. Among many other effects, it increases your body temperature in the second half of the cycle. When the temperature rise has occured, you know: you have ovulated!

However, it is not enough to just measure the temperature once, because the temperature level alone does not tell us how high the progesterone is. So what we need is a temperature history to see that your core body temperature (or the lowest value, the basal body temperature) has risen relative to the other temperature values. The basal body temperature is the lowest core body temperature your body reaches when at rest – that is when you are sleeping. It is usually measured in the second half of the night, i.e. in the very early hours of the morning.

Schwangere Frau hält sich den Bauch.

Basal Body Temperature & Pregnancy

Observing your basal body temperature not only helps you to determine whether you have ovulated, but also whether you may be pregnant – this is particularly interesting for all women who want to have children. After ovulation, the temperature rises and stays at this higher level until the next menstrual period. Then a new cycle begins and your core body temperature drops again. However, if you do not start menstruating and your basal body temperature remains at a higher level for at least 18 days, it may be time for a pregnancy test or a visit to your gynecologist.

  • It is best to measure the basal body temperature inside the body, because: While your body temperature inside the body always remains relatively constant so that your organs can work properly, the temperature on the skin surface is subject to greater fluctuations. The further away from the body core the spot where the temperature is measured, the greater the fluctuations. If you tend to have cold feet or hands in winter, you will be familiar with this effect: The extremities react much faster to cold with lower blood flow than the inside of the body. For the same reason, it is also recommended when taking a temperature that this is best done in the ear, mouth or buttocks. Even under the armpit, the body temperature can sometimes be subject to considerable fluctuations. It is therefore not easy to take meaningful basal body temperature readings, unless you measure inside the body, as the trackle fertility monitor does.

Why should you measure all night to get a good basal value?

Maybe you already know that from literature about the Natural Family Planning or the sympothermal method: there it is often recommended to use the so-called "wake-up temperature" for the evaluation, because the wake-up temperature comes very close to the real basal value.

The wake-up temperature is the temperature that you measure immediately after waking up – always at the same time, for three minutes. In the past, there was no way to measure the real basal body temperature, so wake-up temperature was used. However, regular measurement at the same time is often not easy to implement, especially for women who work shifts, have small children or or otherwise have irregular sleep patterns or daily routines.

The actual, exact basal body temperature can therefore only be measured when you are completely at rest - that is, while you are sleeping!

That's why the trackle fertility monitor is worn like a tampon at night and records the temperature curve, which is then used to determine the basal body temperature – very simple, safe and digital.

  • The basal body temperature can be influenced by so-called "disturbing factors" - whether and to what extent varies from person to person. You can recognize a "disturbed" temperature value by the fact that your temperature suddenly rises for one or two days and then drops again without any other reason being apparent (such as ovulation or an infection).

  • Common confounding factors that affect basal body temperature in many women include:

    – Drug consumption

    – Unusual consumption of alcohol

    – Short/disrupted night’s sleep

    – Stress

    – Time change

    – Cold or illness

For whom is basal body temperature monitoring suitable?

Basal body temperature monitoring for fertility tracking works for almost all women, because the temperature rise around ovulation is a very safe physiological phenomenon: if you ovulate, you have a temperature rise. Also women breastfeeding, women in shift work, women with irregular cylce, women who want to have children and women in any age group.