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What is Personalized Medicine?

An Outcome of the Human Genome Project


Updated September 06, 2013

Personalized medicine considers a person's genetic code among other forms of evidence to determine a diagnosis or tailor a treatment to improve that person's health or cure his medical problem.

There are approximately 25,000 different genes in the genetic code of human beings. They have been "mapped" as a part of the Human Genome Project, an effort undertaken by the U.S. Department of Energy and the National Institutes of Health. This project was completed in 2003.

Understanding what human traits those genes determine and the alterations that may cause human disease or medical problems helps researchers determine forms of treatment or therapies that can be tailored to a specific individual, thus, the development of personalized medicine.

How is Personalized Medicine Different from Traditional Medicine?

The two main forms of medicine practiced in the United States today are allopathic medicine, considered to be traditional, mainstream and "western" medicine, and alternative medicine, also called "eastern" medicine. Both these medical approaches are generalized across human beings. For example, when someone has symptoms of diabetes, they are symptoms that any human with diabetes might have, such as elevated blood sugar levels. Treatment, then, is determined by the knowledge developed by research on an entire population of people with the same blood sugar level problems.

On the other hand, personalized medicine takes a person's genetic code into account when determining how to treat whatever medical problem that person has. In the case of someone with diabetes, any treatment that a specific patient would receive would be based on a combination of diabetes genetic code findings plus generalized knowledge about blood sugar levels, the function of the patient's pancreas and more. (Note: this is only a concept. Genetically-based, personalized diabetes treatments are not yet a reality.)

How Does Personalized Medicine Work?

Personalized medicine is used in two aspects of human medicine: genetic testing for potential abnormalities and tailoring treatment.

The Human Genome Project "mapped" the approximately 25,000 human genes, determining what genes exist in human DNA and what their roles are in a healthy human being. Knowledge of what those genes look and behave like when they are normal means that they can be compared with the genes of patients with medical problems to determine whether those patients' genes are abnormal.

In some cases, a patient is tested when he or she begins to develop symptoms. In others, genetic testing is done prior to development of symptoms. Dozens of tests are already developed, and more tests will be developed over time to make those comparisons.

For example, there are several tests available to determine infection by the hepatitis C virus. One is a genotype test that may determine which form of treatment will work best in a patient. Phase III clinical trials are now underway to confirm this testing.

Once tests are developed to determine abnormalities in human genes, then treatments or therapies for medical problems, which may result, can be developed. In effect, those treatments will be personalized to all human beings with the same genetic abnormality. The gene test results will be considered along with other tests and environmental evidence for each person who needs treatment.

Breast cancer is one disease that is being treated based on genetic information. More than a dozen genes have been associated with breast cancer, and patients can make their treatment decisions based on the knowledge this genetic testing reveals. For example, women who have inherited the BRCA1 or BRCA2 genes know they have a high risk of developing breast cancer, ovarian cancer or other female cancers. Therefore, they may choose to have surgical intervention before they actually develop those cancers.

Learn more about personalized medicine:


The Human Genome Project U.S. Department of Energy and the National Institutes of Health

Marc L. Reitman and Eric E. Schadt Pharmacogenetics of metformin response: a step in the path toward personalized medicine (abstract) The Journal of Clinical Investigation

What is breast cancer? National Institutes of Health

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