FDA Adverse Event Reports (FAERS): How to Read and Report Them (2026)
- What it is: FAERS is the FDA's public database of reported drug side effects and medication errors, fed by MedWatch.
- The biggest trap: a high report count is a safety signal to investigate, never a rate or proof that the drug caused the harm.
- You can report: any patient or clinician can file a MedWatch report of a suspected reaction in about 30 minutes.
Table of contents
By Vincent Couey, OmniRx founder. Source-cited from the FDA, FAERS public dashboard, and the openFDA documentation. Updated .
When a news story claims a drug has "thousands of adverse event reports," it is almost always citing FAERS, and it is almost always being read wrong. The FDA Adverse Event Reporting System is one of the most valuable and most misunderstood public datasets in medicine. Used correctly, it is an early-warning radar for drug safety. Used carelessly, it produces scary-sounding numbers that prove nothing. This guide teaches the difference, and it underpins the OmniRx Drug Safety Explorer, which reads FAERS through openFDA while keeping the caveats front and center.
We cover what FAERS actually contains, the specific ways report counts get misread, how to read an adverse-event profile responsibly, how openFDA exposes the data programmatically, and the step-by-step process for filing your own MedWatch report. The throughline is one discipline: counts are signals, never rates.
What is FAERS?
FAERS is the FDA's database of adverse event and medication error reports for approved drugs and therapeutic biologics. It aggregates reports from two streams: voluntary submissions from patients and HCPs through MedWatch, and mandatory submissions from manufacturers who are legally required to forward reports they receive. Events are coded using a standardized medical dictionary (MedDRA) so that similar reactions can be grouped. The FDA uses the combined dataset for post-marketing surveillance, a core function of pharmacovigilance, looking for new safety signals that did not surface in pre-approval trials.[1] The system's purpose and limits are spelled out in the FDA's FAERS questions and answers.
What FAERS is not is a registry of confirmed, drug-caused harms. A report enters the system because someone suspected a connection, not because anyone proved one. The FDA explicitly states that the existence of a report does not establish that the product caused the event. That single design fact is the key to reading everything else correctly.
Who reviews FAERS reports?
FDA safety evaluators and pharmacovigilance teams mine FAERS for patterns, using statistical signal-detection methods to flag drug-event pairs that report more often than expected. A flagged signal triggers deeper investigation, which can lead to label changes, safety communications, or further study, but the report count itself never makes that decision automatically.
Why do people misread FAERS data?
The core misreading is treating a raw report count as if it were a risk rate, when FAERS has no denominator. To compute a rate you need to know how many people took the drug without harm, and FAERS captures only reports, never total exposure. A drug taken by fifty million people will accumulate more reports than a niche drug taken by fifty thousand, even if the niche drug is far riskier per patient. Counts without exposure data cannot rank danger.
| What FAERS can tell you | Valid use? | What it cannot tell you |
|---|---|---|
| That a suspected reaction has been reported | Yes | That the drug caused it |
| The types of events reported for a drug | Yes | How common the event is per patient |
| A rising signal worth investigating | With caution | A definitive risk rate |
| Raw report counts as a danger ranking | No | Anything reliable on their own |
Three other distortions compound the denominator problem. Stimulated reporting inflates counts after news stories or lawsuits. Underreporting does the opposite for quiet, long-marketed drugs. And duplicate reports, where the same case is submitted by a patient, a doctor, and a manufacturer, can stack. None of these are flaws to fix; they are properties to account for when reading the data.
How do you read a FAERS adverse-event profile correctly?
Reading FAERS correctly means using it for shape and signal, not for ranking or rates. The responsible approach treats a drug's adverse-event profile as a qualitative map of what has been reported, cross-checked against the FDA label and controlled evidence, rather than as a quantitative danger score.
- Start with the label, not the count. If an event is already on the FDA label as a known reaction, FAERS is confirming, not revealing. Unlabeled events that recur are the more interesting signal.
- Look at proportions within a drug, not counts across drugs. What fraction of a drug's reports are serious, or cluster around one organ system, is more meaningful than its total versus another drug.
- Weight serious outcomes. FAERS flags outcomes like hospitalization, disability, and death. A pattern of serious outcomes warrants more attention than a pile of mild ones.
- Never compute your own rate. Without exposure data, any "X percent of users" figure derived from FAERS is invalid. Resist it even when it is tempting.
This is exactly the discipline our drug-interaction checking guide applies: surface the signal, anchor it to the label, and defer causation to controlled evidence. It is also why the OmniRx Drug Safety Explorer labels every count as a report count, never a rate.
What is openFDA and how does it expose FAERS?
openFDA is the FDA's free public API and search layer for its datasets, including FAERS. It lets anyone query adverse-event records, drug labels, recalls, and enforcement reports programmatically, without special credentials, returning structured data, often keyed to a product's NDC, that tools can read directly.[2] The endpoints and fields are documented in the openFDA drug adverse-event API reference. Before openFDA, this data lived in quarterly files that were hard for the public to use; the API made real-time, queryable access the norm.
The OmniRx Drug Safety Explorer sits on top of openFDA, pulling reported side effects, severity breakdowns, and demographic distributions into a readable interface while preserving the caveat that counts are not rates. The point of building on openFDA rather than scraping is provenance: every figure traces back to the FDA's own dataset.
Can I trust a third-party site that shows FAERS numbers?
Trust it only if it makes the same caveats the FDA does: that counts are not rates and reports are not proof of causation. A site that ranks drugs by raw report count, or implies a percentage risk from FAERS alone, is misusing the data regardless of how polished it looks.
How do you file a MedWatch report yourself?
Filing a MedWatch report is a short, free process that any patient can complete, and you do not need to be certain the drug caused the problem. The FDA wants reports of suspected reactions precisely because surveillance depends on volume; your report becomes one data point the system can analyze.
Step 1: Go to the MedWatch reporting page
Open the official FDA MedWatch voluntary reporting form for consumers and patients on fda.gov.
Step 2: Describe the event
Record what happened, when it started, the outcome, and whether the product was stopped or the dose was changed.
Step 3: Identify the product
Enter the product name, dose, and lot number if you have it, plus any other medications taken at the time.
Step 4: Add reporter and patient details
Provide the patient's relevant age and sex and your contact information so the FDA can follow up if needed.
Step 5: Submit and keep a copy
Submit the form and save the confirmation; your report enters FAERS and contributes to national safety surveillance.
The authoritative form, the consumer Form 3500B, lives on the FDA's MedWatch program page. Reporting is especially valuable for newer drugs, where the post-marketing safety picture is still forming, and for unexpected reactions not yet on the label.
- Primary sources
- FDA FAERS public documentation; FDA MedWatch program page; openFDA developer docs
- Verified definitions
- FAERS purpose and limits; "counts are not rates"; two report streams; openFDA free access
- Caveat logged
- Report-count figures are illustrative of structure, not quantitative risk claims
- Conflicts
- OmniRx earns ad and affiliate revenue; the Drug Safety Explorer is a free tool built on openFDA
- Last verified
- May 29, 2026
How should patients actually use this data?
Patients should use FAERS as a conversation starter with a clinician, never as a reason to stop a medication on their own. The data's real value to an individual is in surfacing questions worth asking, not in delivering verdicts. Stopping a needed drug because of a scary report count can cause more harm than the reported event ever would.
If a side effect has you reconsidering a drug on cost grounds as well, compare alternatives and pricing first rather than abandoning therapy; RxGrab's generic-versus-brand guide helps. And if you are layering supplements on top of a prescription, those carry their own under-reported interaction profile, covered in Health Britannica's evidence reviews and our own guide to supplements that interact with medications.
Frequently asked questions
What is the FDA Adverse Event Reporting System (FAERS)?
FAERS is the FDA's database of adverse event and medication error reports submitted for approved drugs and therapeutic biologics. It collects voluntary reports from patients and clinicians through MedWatch and mandatory reports from manufacturers. The FDA uses FAERS for safety surveillance, to detect new safety signals, and to inform label changes and safety communications. The data is public and accessible through the openFDA interface.
Does a high number of FAERS reports mean a drug is dangerous?
No, and this is the single most common misreading. A high report count can reflect how widely a drug is prescribed, how much media attention it has received, or reporting incentives, not just true risk. FAERS reports are not verified as caused by the drug, and the system does not capture how many people took the drug without harm. Report counts are a signal to investigate, never a rate or proof of causation.
How do I report a drug side effect to the FDA?
Use the FDA MedWatch voluntary reporting form, available online, by phone, or by mail. Describe what happened and when, identify the product and dose, and include the lot number if you have it. You do not need to be certain the drug caused the event; the FDA wants reports of suspected reactions. Your report enters FAERS and contributes to national safety surveillance.
What is openFDA and how does it relate to FAERS?
openFDA is a free public API and search interface the FDA provides to query its datasets, including FAERS adverse events, drug labels, and recalls. It lets developers and the public retrieve adverse-event records programmatically without special access. Tools like the OmniRx Drug Safety Explorer use openFDA to surface reported side effects, severity, and demographics in a readable form while preserving the caveat that counts are not rates.
Are FAERS reports proof that a drug caused a side effect?
No. A FAERS report documents a suspected association reported by a patient, clinician, or manufacturer; it is not adjudicated proof of causation. Establishing causation requires controlled studies, pharmacovigilance analysis, and biological plausibility. FAERS is an early-warning surveillance tool that helps the FDA decide what to investigate further, not a verdict on any individual drug-event pair.
The bottom line
FAERS is the FDA's public adverse-event surveillance database, fed by voluntary MedWatch reports and mandatory manufacturer submissions, and exposed for anyone to query through openFDA. Its value is as an early-warning signal, and its single most important limit is that report counts are not risk rates and never prove causation, because the system has no exposure denominator and is distorted by stimulated reporting, underreporting, and duplicates. Read it for shape against the label, file a MedWatch report when you experience a suspected reaction, and treat any number you find as a question for your clinician rather than a verdict on your medication.
- U.S. Food and Drug Administration. Questions and Answers on FDA's Adverse Event Reporting System (FAERS). fda.gov verified 2026-05-29 return
- U.S. Food and Drug Administration. openFDA. open.fda.gov verified 2026-05-29 return