Pharmacologic class (EPC) · 7 drug pages

Biguanide: adverse event reports filed with FDA

116,598 reports list a drug in this class as a suspect or interacting product, 2004–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

116,598
reports across the class: 0.6% of all reports; 7,340
reports, 12 months to June 2026: 7,269 in the 12 months before; 81.3%
marked serious by the reporter: 57.4% across all reports; 7
drugs with a page: brand and generic names counted separately

Biguanide is a pharmacologic class (an FDA Established Pharmacologic Class) with 7 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 116,598 adverse event reports received by FDA, 0.6% of the database, from January 2004 to June 2026.

7,340 reports arrived in the 12 months to June 2026, close to the 7,269 of the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 81.3% of the class's reports are marked serious, 13.9% record death among the outcomes and 43.1% record hospitalisation, as reported.

Across the class the reactions recorded most often are lactic acidosis (16.9%), acute kidney injury (10%) and diarrhoea (8.3%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is 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."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
Metformin	generic	66,495	5,178	87.1%	Lactic acidosis
Metformin hydrochloride	generic	24,187	1,851	80.6%	Lactic acidosis
Metformin hcl	generic	11,314	0	67.2%	Lactic acidosis
JanumetSitagliptin and metformin hydrochloride	brand	10,509	133	64.9%	Blood glucose increased
XigduoDapagliflozin and metformin hydrochloride	brand	2,199	177	76.5%	Diabetic ketoacidosis
InvokametCanagliflozin and metformin hydrochloride	brand	1,336	1	60%	Osteomyelitis
Actoplus MetPioglitazone and metformin hydrochloride	brand	558	0	89.1%	Bladder cancer

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."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Lactic acidosisa build-up of lactic acid in the blood16.9%19,730
Acute kidney injurysudden loss of kidney function10%11,628
Diarrhoealoose or frequent stools8.3%9,653
Toxicity to various agentspoisoning or toxic effect of one or more substances5.7%6,674
Nauseafeeling sick5.5%6,442
Hypoglycaemialow blood sugar5.3%6,225
Vomitingbeing sick5.3%6,153
Metabolic acidosistoo much acid in the body fluids5.3%6,137
Blood glucose increasedraised blood sugar reading5.3%6,123
Drug ineffectivethe medicine did not work as expected5.2%6,116
Hypotensionlow blood pressure3.5%4,040
Completed suicidedeath by suicide3.3%3,859
Dyspnoeashortness of breath3.1%3,667
Fatiguetiredness3.1%3,640
Malaisegeneral feeling of being unwell2.9%3,432
Weight decreasedweight loss2.9%3,399
Drug interactionan interaction between medicines2.8%3,224
Astheniaweakness or lack of energy2.7%3,154
Hyperkalaemiahigh blood potassium2.6%3,072
Dizzinesslight-headedness or unsteadiness2.6%3,070
Renal failurekidney failure2.6%3,010
Headachehead pain2.5%2,864
Overdosea dose above the recommended amount2.4%2,833
Off label useused for a purpose or in a way not on the label2.4%2,806
Abdominal painstomach or belly pain2.4%2,747

Solid bar: share of all class reports. Hollow bar: the median share across the 7 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death13.9%16,183

Life-threatening12.4%14,450

Hospitalisation (initial or prolonged)43.1%50,219

Disability2.7%3,172

Congenital anomaly1.5%1,760

Other serious49.9%58,189

Not serious18.7%21,801

Patient age

Under 20.4%425

2 to 110.2%176

12 to 171%1,120

18 to 448.5%9,881

45 to 6425.9%30,245

65 to 7418.9%22,022

75 and over15.3%17,807

Age not given30%34,922

Who reported

Physician28.3%32,973

Pharmacist8.5%9,928

Other health professional30.4%35,395

Lawyer0.4%429

Consumer or non-health professional28.4%33,077

Not given4.1%4,796

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Biguanide reports

Which drugs are in the Biguanide class on this site?

Metformin, Metformin hydrochloride, Metformin hcl, Janumet, Xigduo and Invokamet and 1 more. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

116,598 reports through June 2026, 7,340 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

lactic acidosis (16.9%), acute kidney injury (10%), diarrhoea (8.3%), toxicity to various agents (5.7%) and nausea (5.5%).

Can the members table be used to rank the drugs?

No. 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." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. 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 class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. 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.