The danger of a person diagnosing his symptoms is that he might be completely wrong about them, according to Psychology Today. A person may look at his symptoms and conclude he has one disease or condition when he really has something else. This may lead the person to do little for a disease that is potentially life threatening or overreact to a condition that is benign or nonexistent.
For example, people misdiagnose psychological symptoms for physical symptoms and vice versa, according to Psychology Today. A person who suffers from panic attacks may assume he is simply suffering from panic attacks. The truth may be that he has a heart condition that causes tachycardia or an irregular heartbeat or a thyroid problem with symptoms of anxiety.
A person who sees a doctor after a wrong self-diagnosis runs the risk of making the doctor-patient relationship more difficult than it needs to be, says Psychology Today. The patient may insist on the doctor treating a disease that he doesn't have or resists what could be life-saving treatment for a condition he does have but doesn't want to acknowledge. Moreover, if the person distrusts his doctor because he is convinced of his self-diagnosis, he may refuse to get a second opinion from another physician.