Which side effects are reported most for metformin?

Nausea (30,587 reports) and diarrhea (28,674) are the reactions named most often in reports to the FDA, as of September 2026, that list a medicine containing metformin, including combination pills. Nausea and diarrhea are known stomach side effects of metformin; high blood sugar may describe the diabetes being treated, and lactic acidosis is a rare but serious known risk. 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, 30,587, followed by Diarrhea (28,674) and High blood sugar (blood glucose increased) (27,705).
  • Loss of appetite has the lowest figure, 12,148, followed by Feeling unwell (12,996) and Weakness (13,616).
  • The highest is 2.5 times the lowest.

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Source and date

Source
U.S. Food and Drug Administration, Adverse Event Reporting System (FAERS) via openFDA
License
Public domain (U.S. government work); source U.S. Food and Drug Administration, openFDA
Data as of
Published

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 September 30, 2026). https://chart.ly/charts/metformin-side-effects-reported (accessed November 4, 2026).

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The data

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The file has the numbers in this table, with the source, license and date. Please credit the source and Chartly. Developers can also get them as JSON (how).

Reported reaction Reports to the FDA naming metformin
Nausea 30,587
Diarrhea 28,674
High blood sugar (blood glucose increased) 27,705
Fatigue 21,809
Vomiting 20,001
Lactic acidosis (acid buildup in the blood) 19,902
Acute kidney injury 18,756
Weight loss 17,655
Shortness of breath 16,956
Dizziness 16,099
Headache 15,374
Pain 14,514
Weakness 13,616
Feeling unwell 12,996
Loss of appetite 12,148

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