There is a number that tells you more than almost anything else in medicine, and most people have never heard of it. It is called number needed to treat. NNT. It answers a very simple question: how many people have to take this thing for one person to get a benefit?
One benefits, ninety-nine do not
If the NNT is 100, then 100 people take it. One benefits. Ninety-nine take it and get nothing. They still get the cost. They still get the side effects. They still get the daily reminder that they are a person with a condition. They just do not get the benefit. That is not a scandal on its own. Sometimes an NNT of 100 is absolutely worth it, especially if the benefit is enormous and the harm is near zero. That is a real and reasonable trade. But you cannot make that trade if nobody tells you the number.
The number can be made to look better without improving
And here is where it gets interesting. NNT can be made to look better without anything actually improving.[1] Stretch the study out over more years. Change what counts as a benefit. Bundle several different outcomes together so a small soft outcome carries the whole result. None of that is lying. All of it is presentation.
You are allowed to ask
I am not here to tell you what to take. I am a nurse, not your prescriber, and decisions about medication belong between you and the person who prescribes it. What I am here to say is that you are allowed to ask. You can walk into any appointment and say: "What is the number needed to treat, and what happens to people who do not take it?" A good clinician will respect that question. Many will not have the number on hand, because we were not taught to think this way either. That is not a reason to stay quiet. That is the reason to ask. Informed consent is not a form you sign. It is a number you understand.
Key Takeaways
- Number needed to treat (NNT) = how many people take something for one person to benefit.
- An NNT of 100 means 99 people get the cost and side effects and no benefit -- sometimes still a fair trade, but only if you know the number.
- NNT can be made to look better with no real improvement: longer studies, changing what counts, bundling outcomes.
- Medication decisions belong between you and your prescriber -- and you are allowed to ask for the NNT and what happens to people who don't take it.
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