Doctor Decoded: Diagnosis vs. Prognosis

Both can help make crucial treatment decisions.

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Your doctor already gave you a diagnosis, but then said they need to run a few more tests before they can confidently give you a prognosis.

Um, what’s the difference?

A diagnosis is the identification of the problem that’s causing symptoms. It comes from Greek meaning “to distinguish or discern.” For example, if you are having digestive problems, a diagnosis determines whether your symptoms are being caused by ulcerative colitis, Crohn’s disease, irritable bowel syndrome, or something else entirely. 

Making a diagnosis requires a variety of tests, including evaluating your medical or family history, taking a biopsy, performing a physical exam, or running X-rays or other imaging tests. 

A diagnosis can also include more specific details about your condition, such as your disease subtype (e.g., plaque psoriasis vs. inverse psoriasis) or cancer stage (e.g. stage I or stage IV).  

A prognosis is more like a prediction of how the diagnosis will affect you. It comes from Greek meaning “to know before.” When making a prognosis, doctors are trying to predict your chance of recovery, relapse, complications, and/or survival.

Both the diagnosis and prognosis can help make treatment decisions. For example, if you are diagnosed with an early-stage skin cancer, the prognosis is probably good: You are expected to be cured with a simple surgery. In this case, you probably won’t need to undergo chemotherapy or other aggressive treatments, which would just cause unnecessary side effects.

On the other hand, if you’ve been diagnosed with a rare type of cancer in which traditional treatments have not been successful, the prognosis might be less optimistic. In this case, you and your doctor may be more willing to try riskier surgeries, novel treatment approaches, or clinical trials.

Got more questions about disease lingo?