Self-diagnosis entails diagnosing, or identifying, medical conditions in oneself. It may be assisted by medical dictionaries, books, resources on the Internet, past personal experiences, or recognizing symptoms or medical signs of a condition that a family member previously had.

Smart sensors perform self-diagnosis by monitoring internal signals for evidence of faults. Although it is difficult to achieve a sensor that can carry out self-diagnosis of all possible faults that might arise, it is often possible to make simple checks that detect many of the more common faults.

Self-diagnosis is often used lately to identify what mental illness you may have without the help of a professional, such as a doctor or a psychiatrist. It may occasionally be useful, but often self-diagnosis is counterproductive and harmful to the person diagnosing themself. Mental illnesses and sicknesses discovered through self-diagnosis may just be slightly inaccurate, or sometimes completely wrong.

Mostly self diagnosis occur due to 1) the lack of resources and funding for a proper diagnosis, 2) the stigma that a particular condition carries.

However, diagnosing yourself wrong can be even deadly for you.