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Understanding Risk

Risks Knowledge

What is the chance of a person in the United States dying from a particular cause?

Test your risk knowledge by dragging each cause into the rectangle you think matches the risk of death. You may be surprised by the answers.

Sources1: National Safety Council, 2007 data; American Heart Association

Information about risks can be expressed in many different ways—from numerical odds to percentages. For example, "one in ten", "ten percent" and "one tenth" all mean the same thing. View the presentations of risk below to see how each compares.

The next time you are discussing medicine risks, ask your healthcare provider to help you view the numbers in a way that helps you fully understand the information.

Learn about statistics2

Example 1: When the risk of a side effect is less common like liver damage

Imagine that in the general population only 1 in 10,000 has a particular event happen to them, for example liver damage. However, when a person takes medicine A, their risk of having the side effect doubles.

This "doubling" of the risk (also called "a 100% increase of risk") is the relative risk. But what is the absolute or actual risk from taking the medicine? The actual risk for anybody taking the medicine is 2 in 10,000, which is still very low. You can see this in the image below.

Example 2: When the risk of a side effect is more common like nausea

Let’s go back to our group of 10,000 people. Imagine that a more common event like nausea happens in 10% of people. Patients taking medicine A have an added 16% increase in risk for nausea.

This 16% increase in risk sounds relatively low compared with the 100% increase in the previous example. But if nausea happens in 10% of people (which means 1,000 in 10,000), then a 16% increase means that 1,116 in 10,000 may now be affected as shown below. This is an extra 116 cases per 10,000 patients treated—which is more than the one extra case in Example 1.

Potential risks must always be weighed against the potential benefits of the medicine. It is also important to understand that there may be things other than taking Medicine A that can change someone’s risk. Overall, risk is unique for every patient. Patients should consider their individual risk in partnership with their healthcare team.


1 National Safety Council. Injury Fact Chart: What Are the Odds of Dying From...
2 American College of Physicians. Primer on Absolute vs. Relative Differences. Effective Clinical Practice. January/February 2000.