Which side effects are reported most for metformin?
Nausea (30,267 reports) and diarrhea (28,320), known stomach side effects of metformin, are the reactions named most often in the roughly 440,000 reports to the FDA, as of June 2026, that list a medicine containing metformin, including combination pills. High blood sugar comes third, which may describe the diabetes being treated; lactic acidosis, a rare but serious known risk, has about 19,000. A report is not proof the medicine caused the problem: anyone can send one, it lists every medicine the person was taking, and the same case can be reported twice. Reports that the medicine didn't work or was used differently than labeled are left out. Don't stop a medicine without talking to a doctor.
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Key facts
Measure: Reports to the FDA naming metformin. Written from the data below.
- Nausea has the highest figure, 30,164, followed by Diarrhea (28,200) and High blood sugar (blood glucose increased) (27,577).
- Loss of appetite has the lowest figure, 11,927, followed by Feeling unwell (12,851) and Weakness (13,438).
- The highest is 2.5 times the lowest.
Source and date
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Citation
Chartly. “Which side effects are reported most for metformin?” Chart. Data: U.S. Food and Drug Administration, Adverse Event Reporting System (FAERS) via openFDA, https://open.fda.gov/apis/drug/event/ (data as of June 30, 2026). https://chart.ly/charts/metformin-side-effects-reported (accessed October 15, 2026).
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The data
Download data (CSV)The file has the numbers in this table, with the source, license and date. Please credit the source and Chartly.
| Reported reaction | Reports to the FDA naming metformin |
|---|---|
| Nausea | 30,164 |
| Diarrhea | 28,200 |
| High blood sugar (blood glucose increased) | 27,577 |
| Fatigue | 21,487 |
| Vomiting | 19,617 |
| Lactic acidosis (acid buildup in the blood) | 19,399 |
| Acute kidney injury | 18,251 |
| Weight loss | 17,507 |
| Shortness of breath | 16,731 |
| Dizziness | 15,837 |
| Headache | 15,122 |
| Pain | 14,276 |
| Weakness | 13,438 |
| Feeling unwell | 12,851 |
| Loss of appetite | 11,927 |
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