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The most commonly reported drug side effects

Across every medication in the FDA's adverse-event database, these symptoms are reported the most.

Data updated 2026-05-15

25.9M
Reaction reports
683
Distinct reaction terms
524
Medications

Fatigue is the side effect reported most often to the FDA Adverse Event Reporting System (FAERS) across PlainMeds-tracked drugs, appearing in 1,494,557 reports across 457 medications.

PlainMeds ranks the clinical side effects reported most often to FDA FAERS across the medications it tracks. Fatigue, Nausea, and Pain lead. A high report count reflects how often a reaction is reported, not how likely it is to happen to any one patient, and widely used drugs naturally accumulate more reports. Report volume is not a measure of incidence or causation.

According to the U.S. Food and Drug Administration (FDA), Fatigue is the single most-reported side effect in the FDA Adverse Event Reporting System (FAERS), appearing in 1,494,557 reports across 457 medications. Compiled from cumulative FAERS data, the list below ranks the 25 clinical reactions reported most often. Report volume reflects how widely a drug is used and how often an effect is reported, not how likely you are to experience it; see our methodology for how these figures are compiled.

Most-reported side effects by FAERS report volume

Value

What this shows Fatigue and Nausea top the list; both appear in reports for hundreds of different medications.

Source FDA FAERS (cumulative reaction reports)

Top 25 reported side effects

# Side effect FAERS reports Medications
1 Fatigue 1,494,557 457
2 Nausea 1,354,154 456
3 Pain 1,260,221 343
4 Diarrhoea 1,074,344 390
5 Headache 1,026,225 397
6 Dyspnoea 969,495 365
7 Arthralgia 808,949 202
8 Vomiting 720,509 333
9 Dizziness 692,271 335
10 Malaise 551,353 229
11 Rash 550,367 170
12 Asthenia 497,362 225
13 Death 493,056 205
14 Fall 482,974 225
15 Pneumonia 400,746 183
16 Rheumatoid Arthritis 371,845 34
17 Condition Aggravated 355,025 165
18 Pyrexia 338,868 178
19 Acute Kidney Injury 282,591 142
20 Pain In Extremity 256,863 72
21 Joint Swelling 256,311 31
22 Pruritus 244,551 115
23 Anxiety 217,939 143
24 Injection Site Pain 192,299 20
25 Toxicity To Various Agents 182,075 69

How to read this list

These counts come from the FDA's Adverse Event Reporting System (FAERS), a database of more than 25 million voluntary reports collected since 2004 from patients, doctors, and manufacturers. Two things matter when reading them:

  • Volume is not incidence. A side effect reported many times is one that is reported often, which tracks how widely the underlying drugs are used and how noticeable the effect is. It does not tell you the percentage of people who experience it.
  • These are clinical reactions only. FAERS also records administrative terms such as "drug ineffective" and "off-label use" that are not symptoms; those are excluded here so the ranking reflects real side effects.

A report in FAERS does not mean the drug caused the effect, only that someone reported it while taking the drug. Always read a specific medication's own label and talk to your pharmacist about side effects that concern you. You can also search any medication on PlainMeds to compare its own reported side-effect profile against this list.

Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.

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