If you sat down expecting the FDA's adverse event data to be a catalog of dramatic, dangerous side effects, the real numbers would surprise you. The most frequently reported event across every medication we track is not a rash, a heart problem, or anything a doctor would call a reaction. It is "drug ineffective," the formal way of recording that a medication simply did not work.
It shows up more than 6 million times. And it is not alone near the top. Of the five most-reported events in the data, two are not bodily reactions at all.
We pulled together the FDA's adverse event reports for 849 medications and looked at the patterns across all of them. The system that holds this data is now the FDA's Adverse Event Monitoring System (AEMS), formerly FAERS. Here is what stood out.
The most common "adverse event" is that the drug didn't work
Across the 849 medications, the five most frequently reported events are:
- Drug ineffective, about 6.1 million reports
- Fatigue, about 4.9 million
- Off label use, about 4.6 million
- Nausea, about 4.4 million
- Pain, about 4.1 million
"Drug ineffective" and "off label use" are the two that are not side effects in the way most people picture them. The first means someone reported that the medication did not do its job. The second means it was used for something other than its FDA-approved purpose, which is extremely common, often perfectly appropriate medical practice, and still gets logged. "Drug ineffective" is a top-three event for just over half of the medications we track — 429 of the 849.
This is the first instinct to bring to all of this data: a lot of what gets reported is not harm. People report when a drug fails them, not only when it hurts them. So a large pile of reports for a medication tells you it has generated a lot of reporting activity, not that it is dangerous.
The 2004 cliff
If you chart the reports by year, the most striking feature has nothing to do with any drug. It is a cliff in 2004.
Before 2004, the data shows almost nothing — under 2,000 reports a year. Then in 2004 it leaps to more than 800,000, and it climbs steadily from there: about 4.1 million reports in 2015, 5.6 million in 2018, and somewhere between 5.7 and 6 million a year from 2019 through 2025.
This is not because medications suddenly became more dangerous in 2004. It is roughly when the FDA moved to electronic submission, and reporting volume exploded as a result. This matters enormously for reading any trend. If you see a drug's reports rising over the years, a large part of that rise may simply be that the whole system started capturing far more reports over time. The shape of the data is driven by how reporting works, not only by what is happening to patients.
Who shows up in the reports
Across the roughly 70 million reports that record a patient's sex, about 60 percent are women and about 40 percent are men. By age, around 70 percent of reports involve people 50 or older, with the 50-to-64 group the single largest at roughly 29 percent.
It is tempting to read something dramatic into that, but the careful reading is more boring and more accurate. These splits mostly reflect who takes more medications and who files more reports, not who is secretly at greater risk. Older adults are on more prescriptions. Patterns in who seeks care and who reports differ by sex. The data describes the people in the reports, not the entire population taking these drugs.
What happened to the people in the reports
The FDA codes each report for outcomes, and a single report can carry more than one. Across all the outcome codes in the data:
- Other serious outcomes: about 36 percent
- Hospitalization: about 26 percent
- Non-serious: about 22 percent
- Death: about 9 percent
- Life-threatening: about 4 percent
- Disability: about 3 percent
At a glance, the heavy share of "serious" outcomes looks alarming. Here is the context that changes how you read it: serious events are far more likely to be reported in the first place. A mild, expected side effect rarely prompts anyone to file a report, while a hospitalization often does. So the high proportion of serious outcomes reflects what motivates people to report, not the true rate of serious harm among everyone who takes these medications.
The death figure deserves the most care of all. A report coded as a death means someone who was taking the medication died and a report was filed. It does not mean the medication caused the death, and the data cannot tell you that it did. People who take medications are often already seriously ill, and a death recorded alongside a drug is not evidence the drug was responsible.
A note on the numbers
The 78 million figure is the sum of report counts across the 849 medications we track. It is deliberately not presented as the number of unique reports in the FDA's system, and it is larger than that true total, for a straightforward reason: a single report often names more than one medication, and the same report then appears under each drug it mentions. We also curated the data before counting, removing duplicate store-brand listings and entries that were not really medications, so that each drug is represented once rather than dozens of times. Read 78 million as a measure of how much reporting activity these medications have collectively drawn, not as a headcount of individual people or events.
How to actually use this
The value of this data is not in any single big number. It is in learning to read it with the right instincts: that reports include failures and off-label use, not just harm; that long-term trends are shaped by how reporting itself changed; that the demographics describe who reports; and that even serious-looking outcomes reflect reporting behavior more than true rates, with death counts especially prone to misreading.
Read that way, the FDA's data is a genuinely useful starting point. It can show you what other people have reported about a medication you have been prescribed, which is a good thing to know walking into a conversation with your doctor or pharmacist. What it cannot do is tell you whether a drug is safe for you, or whether it caused anything. Those are questions for a professional who knows your situation, with this data as one input among many.
To go deeper on reading a single drug's page, see our guide on how to read FDA adverse event reports. And if you are wondering why the system is now called AEMS, we explain that change in our guide on what AEMS is.
Had an experience with a medication? How to Report a Drug Side Effect to the FDA →
The system behind this data has a new name — What Is AEMS? The FDA System That Replaced FAERS →
Ready to look up a medication? Search PillSignal →
Last updated: June 2026