A boxed warning for lactic acidosis has been added to the label for metformin hydrochloride, effective January 1, 2026. This warning highlights postmarketing cases of metformin-associated lactic acidosis that have resulted in serious adverse outcomes, including death, hypothermia, hypotension, and resistant bradyarrhythmias. The onset of this condition is often subtle, making early recognition challenging.
Background
Metformin hydrochloride is a widely prescribed oral antihyperglycemic agent used in the management of type 2 diabetes mellitus. It belongs to the biguanide class of drugs and works primarily by decreasing hepatic glucose production, decreasing intestinal absorption of glucose, and improving insulin sensitivity by increasing peripheral glucose uptake and utilization. It is often used as a first-line treatment, either as monotherapy or in combination with other antidiabetic medications. For instance, it is frequently co-formulated with drugs like canagliflozin, an SGLT2 inhibitor, in combination products such as Invokamet and Invokamet XR, to provide comprehensive glycemic control.
What this means
The addition of a boxed warning for lactic acidosis on the metformin hydrochloride label reinforces the importance of monitoring patients for this rare but serious adverse event. Lactic acidosis, while uncommon, can be fatal if not promptly recognized and treated. Clinicians should be vigilant for symptoms such as malaise, myalgia, respiratory distress, somnolence, and abdominal pain, particularly in patients with predisposing factors like renal impairment, concomitant use of certain drugs, or conditions leading to hypoxemia. The warning also notes that the onset of metformin-associated lactic acidosis is often subtle, making early diagnosis challenging. This label change serves as a critical reminder for healthcare providers to assess patient risk factors, educate patients on potential symptoms, and consider discontinuing metformin in the presence of factors that may increase the risk of lactic acidosis.
Source
This information regarding the label revision for metformin hydrochloride was sourced from the FDA, as documented on DailyMed, a service of the National Library of Medicine. The label update, effective January 1, 2026, is available on dailymed.nlm.nih.gov.