Several types of misdiagnoses occur and harm patients. Doctors get things wrong, take too long to arrive at the correct conclusion, fail to account for all symptoms and test results, and fail to notice that their patient is suffering from more than one health problem. The reasons doctors make such errors vary, and the causes can be related.

Cognitive bias, or seeing things through a specific lens, is a major cause of misdiagnoses. Doctors tend to treat certain patients in certain ways, and they often make the same diagnoses over and over again.

Time pressures also lead many doctors to rush to conclusions about what ails their patients. A doctor who spends too little time interviewing patients about symptoms and medical histories can easily miss essential information.

Bias and time pressures can then compound or cause other issues such as failing to order appropriate tests, doing tests incorrectly, misinterpreting test results, failing to communicate with other health care providers and ignoring new or worsening symptoms.