Metformin Side Effects are documented on the FDA prescribing label, and reported separately by patients and doctors to the FDA’s adverse event system. This page sets out what the official record actually says about Metformin: what it is approved to treat, what the label warns about, its recall history, and what the reported side effects are — along with what those figures do and do not mean.
- What Metformin Is Prescribed For, and Where Metformin Side Effects Come From
- The FDA Boxed Warning on Metformin
- Warnings Beyond the Common Metformin Side Effects
- Metformin Side Effects Listed on the FDA Label
- Reported Metformin Side Effects in the FDA Database
- Who the Label Says Should Take Extra Care
- Metformin Recall History
- Is Metformin the Subject of Litigation?
- If You Are Worried About Metformin Side Effects
- Frequently Asked Questions
- Official Sources
- Related Guides
Before you read on. Do not stop taking a prescribed medicine, or change how you take it, because of anything you read here. Talk to the prescriber or pharmacist who knows your medical history first.
What Metformin Is Prescribed For, and Where Metformin Side Effects Come From
According to the FDA label, etformin hydrochloride extended-release tablets are indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. Metformin hydrochloride extended-release tablets are a biguanide indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. ( 1 )
Two separate official sources describe metformin side effects. The prescribing label records what was observed in clinical trials, where the drug was compared against a control group. The FDA’s adverse event database records what patients and clinicians have reported since approval, which is a much larger but far less controlled picture. Both appear below, and they answer different questions.
| Active ingredient | Metformin Hydrochloride |
| Brand names on this label | METFORMIN HYDROCHLORIDE |
| How it is given | oral |
| Boxed warning | Yes – see below |
| Recall records | 43 |
| Label last updated | 2025-06-30 |
The FDA Boxed Warning on Metformin
This medicine carries a boxed warning
WARNING: LACTIC ACIDOSIS Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. The onset of metformin-associated lactic acidosis is often subtle, accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, somnolence, and abdominal pain. Metformin-associated lactic acidosis was characterized by elevated blood lactate levels (>5 mmol/Liter), anion gap acidosis (without evidence of ketonuria or ketonemia), an increased lactate/pyruvate ratio; and metformin plasma levels generally >5 mcg/mL [ see Warnings and Precautions (5.1) ] . […]
A boxed warning is the most serious warning the FDA requires on a prescription label. It does not mean the medicine should not be used. It means there is a specific risk serious enough that the FDA requires it to appear at the very top of the prescribing information, so that prescribers weigh it deliberately for each patient.
Prescribers see this warning every time they consult the label. If it concerns you, it is a reasonable thing to raise at your next appointment and ask how it applies to your own situation.
Warnings Beyond the Common Metformin Side Effects
The label’s warnings and precautions section describes risks the FDA requires prescribers to weigh. For Metformin it covers: actic Acidosis: See boxed warning . ( 5.1 ) Vitamin B 12 Deficiency: Metformin may lower vitamin B 12 levels. Measure hematological parameters annually and vitamin B 12 at 2 to 3 year intervals and manage any abnormalities. ( 5.2 ) Hypoglycemia with Concomitant Use with Insulin and Insulin Secretagogues: Increased risk of hypoglycemia when used in combination with insulin and/or an insulin secretagogue.
Lower dose of insulin or insulin secretagogue may be required. ( 5.3 ) 5.1 Lactic Acidosis There have been postmarketing cases of metformin-associated lactic acidosis, including fatal cases. These cases had a subtle onset and were accompanied by nonspecific symptoms such as malaise, myalgias, abdominal pain, respiratory distress, or increased somnolence; however, hypotension and resistant bradyarrhythmias have occurred with severe acidosis. […]
These are the risks the FDA has judged significant enough to state formally, and they sit apart from the routine metformin side effects most people ask about. They apply to different patients to very different degrees, which is why the same medicine can be routine for one person and unsuitable for another.
Metformin Side Effects Listed on the FDA Label
The label’s adverse reactions section records what was observed in clinical trials: he following adverse reactions are also discussed elsewhere in the labeling: Lactic Acidosis [ see Boxed Warning and Warnings and Precautions (5.1) ] Vitamin B 12 Deficiency [ see Warnings and Precautions (5.2) ] Hypoglycemia [ see Warnings and Precautions (5.3) ] Common adverse reactions are diarrhea, nausea/vomiting, abdominal pain, constipation, abdomen distention, dyspepsia/heartburn, flatulence, dizziness, headache, upper respiratory infection, taste disturbance. […]
Trial data is the most reliable source for how common metformin side effects are, because the people taking the drug were compared against people who were not. A symptom that appeared just as often in the control group is not caused by the medicine.
Reported Metformin Side Effects in the FDA Database
Reported metformin side effects — and what these numbers do not mean
The FDA’s adverse event database holds 433,187 reports mentioning Metformin, of which 289,276 were classified as serious.
Read those numbers carefully. An adverse event report means somebody told the FDA that something happened to a person taking this medicine. It is not a finding that the medicine caused it. Reports are submitted voluntarily by patients, families, doctors and manufacturers; nobody verifies them; and the same event can be reported more than once.
Report volume tracks how many people take a drug, how new it is, and how much attention it is getting. A widely prescribed medicine will always show more reports than a rarely used one, and reports rise sharply when a drug is in the news or in litigation. A large number here does not mean a drug is dangerous, and a small number does not mean it is safe.
| Most frequently reported | Reports |
|---|---|
| Nausea | 29,720 |
| Diarrhoea | 27,711 |
| Blood Glucose Increased | 27,484 |
| Fatigue | 21,184 |
| Vomiting | 19,221 |
| Lactic Acidosis | 18,812 |
| Acute Kidney Injury | 17,807 |
| Weight Decreased | 17,360 |
Source: FDA Adverse Event Reporting System (FAERS), retrieved July 2026. Non-clinical reporting categories such as “off label use” have been excluded from the list above because they describe how a drug was used, not something that happened to a patient.
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Who the Label Says Should Take Extra Care
Contraindications. The label states that Metformin should not be used in certain situations: etformin hydrochloride extended-release tablets are contraindicated in patients with: Severe renal impairment (eGFR below 30 mL/min/1.73 m 2 ) [ see Warnings and Precautions (5.1) ]. Hypersensitivity to metformin. Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma. […]
Interactions with other medicines. able 2 presents clinically significant drug interactions with Metformin hydrochloride extended-release tablets. Table 2: Clinically Significant Drug Interactions with Metformin hydrochloride extended-release tablets Carbonic Anhydrase Inhibitors Clinical Impact: Carbonic anhydrase inhibitors frequently cause a decrease in serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. […]
Older adults. 8.5 Geriatric Use Controlled clinical studies of Metformin hydrochloride extended-release tablets did not include sufficient numbers of elderly patients to determine whether they respond differently from younger patients. […]
Your pharmacist can check your full medicine list against this in a couple of minutes, including anything bought over the counter, and that check is free.
Metformin Recall History
The FDA enforcement database records 43 recall entries involving Metformin products (38 Class II, 5 Class III). A recall almost always concerns specific manufactured batches rather than the medicine itself, and different manufacturers of the same generic drug have separate recall records.
The FDA classifies recalls by how serious the potential consequence is. Class I means a reasonable probability of serious harm or death; Class II means temporary or reversible harm is possible; Class III means the product breaks a regulation but is unlikely to cause harm.
| Date | Class | Recalling firm | Reason |
|---|---|---|---|
| 2025-04-16 | Class II | Glenmark Pharmaceuticals Inc., USA | CGMP Deviations |
| 2025-04-02 | Class II | A-S Medication Solutions LLC | Presence of Foreign Tablets/Capsules. |
| 2025-01-15 | Class II | Granules Pharmaceuticals Inc. | Presence of Foreign Tablets/Capsules: A Paracetamol 500 mg tablet was found in a 1000-count bottle of Metformin HCL ER Tablets USP, 500 mg. |
| 2022-04-13 | Class II | MERCK SHARP & DOHME CORP | Presence of foreign substance: Presence of stainless steel particulates in tablets. |
| 2022-02-02 | Class II | VIONA PHARMACEUTICALS INC | CGMP Deviations- Detection of N-Nitrosodimethylamine (NDMA) levels in excess of the Acceptable Daily Intake Limit. |
If a batch you have was recalled, the pharmacy that dispensed it is the fastest way to find out and to get a replacement. Do not simply stop taking a prescribed medicine because a recall notice exists — the recall may not affect your batch, and stopping can carry its own risk.
Is Metformin the Subject of Litigation?
We are not tracking consolidated federal litigation over Metformin. It is a widely prescribed medicine, and the information on this page is drawn from the FDA label and public safety data rather than from any legal claim.
If You Are Worried About Metformin Side Effects
Concern about metformin side effects is a good reason to have a conversation, and not a reason to act alone. Do not stop taking a prescribed medicine, or change how you take it, because of anything you read here. Talk to the prescriber or pharmacist who knows your medical history first. Stopping some medicines abruptly carries risks of its own, and your prescriber can tell you whether that applies to yours.
Write down what you have noticed and when it started before the appointment. Not everything that happens while taking a medicine is one of its metformin side effects, and a specific account — what changed, when, and how often — is what lets a clinician tell the difference.
You can also report a side effect directly to the FDA through MedWatch. Reports from patients are part of how safety signals are detected, and filing one takes a few minutes.
Frequently Asked Questions
What are the most commonly reported metformin side effects?
In FDA reports, the most frequently mentioned are nausea, diarrhoea, blood glucose increased. The label’s own adverse reactions section, drawn from clinical trials, is the better guide to how common a side effect actually is, because reports to the FDA are not collected in a way that supports rates.
Has Metformin been recalled?
There are 43 recall records for Metformin products, the most recent dated 2025-04-16. Recalls generally affect specific manufactured batches rather than the medicine as a whole. Your pharmacy can tell you whether a batch you have was affected.
Does Metformin have a boxed warning?
Yes. The boxed warning is reproduced above. It is the most serious warning the FDA requires, and it exists so that prescribers weigh a specific risk for each patient rather than overlooking it.
Do the FDA report numbers tell me how common these metformin side effects are?
No. Reports are unverified, anyone can file one, and the total mostly reflects how many people take the medicine and how much attention it is getting. A high count is not evidence of danger, and a low one is not evidence of safety. Clinical trial data on the label is the source that supports rates.
Where can I check metformin side effects for the exact product I have?
DailyMed holds the current FDA label for every marketed product, searchable by the name on your packaging. Different manufacturers and formulations of the same medicine can have slightly different labels, so checking the one you actually have is worth the two minutes.
Official Sources
- DailyMed (National Library of Medicine) — the current FDA prescribing label for every product
- FDA Adverse Event Reporting System dashboard — the public report data summarised above
- FDA recalls and safety alerts — current recall notices
- FDA MedWatch — how to report a side effect yourself
Related Guides
Medical and legal disclaimer. This page summarises publicly available FDA data about Metformin and is general information, not medical advice, and not legal advice. It is not a substitute for the judgement of a clinician who knows your medical history. Nothing here states that Metformin caused any illness or injury in any individual. Adverse event reports are unverified and do not establish causation.
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FDA labels are revised regularly; confirm current information on DailyMed or with your pharmacist. Do not stop taking a prescribed medicine, or change how you take it, because of anything you read here. Talk to the prescriber or pharmacist who knows your medical history first.