Generic name
Metformin: adverse event reports filed with FDA
66,495 reports list it as a suspect or interacting product, 2004–2026. Class: Biguanide. Also reported as Metformin 500mg, Metformin 850mg, Metformin 1000mg.
- 66,495
- reports as suspect product
- 0.3% of all reports · about 2,978 a year
- 5,178
- reports, 12 months to June 2026
- 4,883 in the 12 months before
- 87.1%
- marked serious by the reporter
- 81.3% across the class
- 14.9%
- record death among outcomes, as reported
- 9,910 reports · not verified by FDA
66,495 adverse event reports received by FDA list metformin, a generic name as a suspect or interacting product, from March 2004 to June 2026. A further 237,665 reports list it only as a concomitant medication, and those are not counted in the figures on this page.
In the 12 months to June 2026, 5,178 reports listed it, close to the 4,883 of the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 2,978 reports a year and 0.3% of the 20,646,523 reports in the database, and 57% of the reports for the biguanide class. How many people take it is not in the data, so a count is not a rate of occurrence.
The reactions recorded most often are lactic acidosis (19.3%), acute kidney injury (12.5%) and diarrhoea (8.4%). A report can list several reactions, so shares add to more than 100%; 3,646 different terms appear across these reports. Lactic acidosis is recorded in 19.3% of these reports, a larger share than in the median biguanide drug (4.7%).
87.1% of the reports are marked serious by the reporter (81.3% across the class); 14.9% record death among the outcomes and 46.6% record hospitalisation, as reported. 32.8% of the reports came from other health professionals, and the largest patient age group is 45 to 64 (26.3%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
Reports by month, five years
Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.
By year received
2026 covers reports received through June 2026 only.
Reactions recorded in the reports
share of Metformin reports recording the termmedian drug in biguanide
- Lactic acidosisa build-up of lactic acid in the blood19.3%12,812
- Acute kidney injurysudden loss of kidney function12.5%8,344
- Diarrhoealoose or frequent stools8.4%5,559
- Toxicity to various agentspoisoning or toxic effect of one or more substances7.5%4,957
- Metabolic acidosistoo much acid in the body fluids6.3%4,199
- Hypoglycaemialow blood sugar5.9%3,927
- Drug ineffectivethe medicine did not work as expected5.5%3,665
- Nauseafeeling sick5.4%3,603
- Vomitingbeing sick5.3%3,529
- Blood glucose increasedraised blood sugar reading4.3%2,846
- Completed suicidedeath by suicide4%2,685
- Hypotensionlow blood pressure3.9%2,590
- Fatiguetiredness3.5%2,336
- Dyspnoeashortness of breath3.3%2,202
- Drug interactionan interaction between medicines3.2%2,145
- Malaisegeneral feeling of being unwell3%2,026
- Weight decreasedweight loss3%2,003
- Hyperkalaemiahigh blood potassium3%1,972
- Astheniaweakness or lack of energy2.8%1,862
- Renal failurekidney failure2.8%1,834
- Off label useused for a purpose or in a way not on the label2.7%1,804
- Headachehead pain2.7%1,776
- Overdosea dose above the recommended amount2.6%1,743
- Dizzinesslight-headedness or unsteadiness2.6%1,696
- Intentional overdosea deliberate overdose2.4%1,582
- Abdominal painstomach or belly pain2.3%1,547
- Painpain, site not specified2.3%1,517
- Condition aggravatedthe condition being treated got worse2.2%1,495
- Confusional stateconfusion2.1%1,416
- Arthralgiajoint pain2.1%1,375
Top 30 of 3,646 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 7 drugs in the biguanide class; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Outcomes recorded
Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 116,598 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."
Patients and reporters
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 34.7% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Type 2 diabetes mellitus | 17,760 | 26.7% |
| Diabetes mellitus | 11,625 | 17.5% |
| Suicide attempt | 357 | 0.5% |
| Polycystic ovaries | 276 | 0.4% |
| Gestational diabetes | 249 | 0.4% |
| Glucose tolerance impaired | 199 | 0.3% |
The indication field is filled in by the reporter and is often blank; shares are of all 66,495 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Metformin reports |
|---|---|---|
| Atorvastatin | 5,280 | 7.9% |
| Amlodipine | 4,541 | 6.8% |
| Aspirin | 4,216 | 6.3% |
| Ramipril | 4,013 | 6% |
| Furosemide | 3,995 | 6% |
| Gliclazide | 3,423 | 5.1% |
| Bisoprolol | 3,127 | 4.7% |
| Simvastatin | 3,057 | 4.6% |
| Omeprazole | 2,747 | 4.1% |
| Lisinopril | 2,675 | 4% |
Other products listed in reports where Metformin is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.
In context
| Measure | Metformin | Biguanide | All reports |
|---|---|---|---|
| Reports as suspect product | 66,495 | 116,598 | 20,646,523 |
| Share of that pool | — | 57% | 0.3% |
| Reports, latest 12 months | 5,178 | — | 1,332,454 |
| Marked serious | 87.1% | 81.3% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 149 | 139 | 91 |
| Hospitalisation recorded, per 1,000 reports | 466 | 431 | 213 |
| Consumer-filed share | 21.6% | 28.4% | 45.8% |
| Top term, share of reports | Lactic acidosis 19.3% | median 4.7% | 0.2% |
Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Other drugs in the biguanide class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Metformin hydrochloride | generic | 24,187 | 1,851 | 80.6% |
| Metformin hcl | generic | 11,314 | 0 | 67.2% |
| Janumet | brand | 10,509 | 133 | 64.9% |
| Xigduo | brand | 2,199 | 177 | 76.5% |
| Invokamet | brand | 1,336 | 1 | 60% |
| Actoplus Met | brand | 558 | 0 | 89.1% |
Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." A brand and its generic are separate rows because reporters name them separately.
Questions about Metformin reports
How many adverse event reports has FDA received for Metformin?
66,495 reports list Metformin as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 5,178 of them arrived in the latest 12 months. Another 237,665 list it only as a concomitant medication.
What reactions are recorded in Metformin reports?
lactic acidosis (19.3%), acute kidney injury (12.5%), diarrhoea (8.4%), toxicity to various agents (7.5%) and metabolic acidosis (6.3%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Metformin was responsible.
How serious are the reports?
87.1% are marked serious by the reporter. Among the outcomes recorded, 14.9% of reports include death and 46.6% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
other health professional (32.8%), physician (32%) and consumer or non-health professional (21.6%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Metformin rising?
5,178 reports in the 12 months to June 2026, close to the 4,883 of the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Metformin was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Metformin?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. See the guide on how to report.
Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Metformin as a suspect or interacting product; reports listing it only as a concomitant medication (237,665) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.
Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.