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Doctor Decoded: Diagnosis vs. Prognosis

In this video, learn the difference between diagnosis and prognosis and why each is important for making treatment decisions.

Lauren SmithPreeti Parikh, MD
Written by Lauren Smith | Reviewed by Preeti Parikh, MD
Published on May 6, 2020

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?


Definition of diagnosis. Bethesda, MD: National Cancer Institute. (Accessed on March 11, 2020 at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/diagnosis.)

Definition of prognosis. Bethesda, MD: National Cancer Institute. (Accessed on March 11, 2020 at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/prognosis.)

View All References (2)

Halabi S, Owzar K. The importance of identifying and validating prognostic factors in oncology. Semin Oncol. 2010 Apr;37(2):e9-18.

What is the prognosis of a genetic condition? Washington, DC: Genetics Home Reference, U.S. National Library of Medicine. (Accessed on March 11, 2020 at https://ghr.nlm.nih.gov/primer/consult/prognosis.)

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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