It is not possible to use a trackle that has been used by someone else. Here is why:

As a certified medical and hygienic product, trackle must meet high legal requirements, which include strict regulations to protect against possible health consequences. Passing on the sensor is therefore not possible and explicitly prohibited, as stated in the instructions for use. 

A trackle sensor can only be linked to one user account once in its lifetime. In addition to a possible risk of infection, the data of two different persons would be mixed if the sensor were used by more than one user. This means that the calculation bases for the fertile period can no longer be used and the contraceptive safety of the system is no longer guaranteed. 

As a result, there is a risk of becoming pregnant unintentionally.

Disregarding and reselling an already used trackle sensor to a third party is considered as use contrary to the intended purpose. As a consequence, the user account of the respective sensor will be blocked immediately.

If you purchase a sensor privately, please note the following: 

The sensor should always be in its original packaging (sealed bag around the sensor undamaged) and should never have been paired with another trackle account, so that you can use it safely. 

Tip: Ask the seller to provide you with the serial number of the sensor and contact our support team at We will be happy to check whether the sensor is still uncoupled.