Metformin

The reviewed immediate-release tablets are labeled for adults and children aged 10 years and older with type 2 diabetes. The reviewed ER tablets are labeled for adults; their pediatric safety and effectiveness have not been established.

• ADA 2026 supports considering prevention in adults at high diabetes risk, especially ages 25–59 with BMI ≥35 kg/m², higher fasting glucose or A1C, or previous gestational diabetes. It also discusses prevention of hyperglycemia in selected high-risk patients receiving PI3Kα inhibitors or high-dose glucocorticoids.
• The international PCOS guideline supports selected metabolic uses, especially adult BMI ≥25 kg/m², and selected cycle-regulation uses with limited adolescent evidence. These are outside the reviewed U.S. diabetes indication and require an individualized plan.

Metformin does not treat diabetic ketoacidosis and is contraindicated in metabolic acidosis. The label does not establish conclusive macrovascular risk reduction; do not equate glucose lowering with proven cardiovascular protection for this product.

Swallow whole; do not cut, crush or chew. A missed ER dose should not be doubled or replaced with two doses that day; resume the usual next scheduled dose. Other ER brands have different labels.

Start 500 mg twice daily with meals. Increase by 500 mg weekly if needed and tolerated; maximum 2,000 mg/day in two divided doses. This schedule does not establish pediatric use of the reviewed ER product.

Check eGFR before treatment and periodically. The label provides no standard dose-reduction formula for continued therapy below 45. Avoid use in hepatic impairment because of lactic-acidosis risk.

Hold at or before iodinated contrast if eGFR is 30–60, there is a history of liver disease, alcoholism or heart failure, or contrast is intra-arterial. Recheck eGFR after 48 hours and restart only if stable. Temporarily stop while surgical/procedural food and fluid intake is restricted; agree the restart plan with the treating team.

For PCOS, the guideline suggests a low starting dose and 500 mg increases every 1–2 weeks, with suggested ceilings of 2.5 g/day in adults and 2 g/day in adolescents. This does not confer pediatric ER approval. Prevention regimens should follow the selected guideline and clinician plan rather than a universal diabetes-label maximum.

• eGFR below 30 mL/min/1.73 m².
• Hypersensitivity to metformin.
• Acute or chronic metabolic acidosis, including diabetic ketoacidosis with or without coma.

Metformin-associated lactic acidosis has been fatal. The boxed warning lists renal and hepatic dysfunction, contrast, surgery, hypoxic states, excessive alcohol, mitochondrial disease and selected interactions among important risk factors.

Diarrhea, nausea/vomiting and other gastrointestinal symptoms are common; IR and ER trial frequencies differ and are not interchangeable. Long-term therapy can lower vitamin B12. Insulin or secretagogue combinations can cause hypoglycemia. Postmarketing liver injury has been reported. Suspected overdose requires urgent assessment; contact U.S. Poison Control at 1-800-222-1222.

• Carbonic-anhydrase inhibitors such as topiramate, zonisamide and acetazolamide promote acidosis: consider more frequent monitoring.
• Renal transporter inhibitors such as cimetidine, dolutegravir, ranolazine and vandetanib increase metformin exposure: assess the benefit and lactic-acidosis risk.
• Alcohol impairs lactate handling: avoid excessive acute or chronic intake.
• Insulin or sulfonylureas increase hypoglycemia risk: their doses may need reduction.
• Corticosteroids, thiazides, thyroid hormones and other hyperglycemia-promoting medicines can worsen control: monitor glucose when starting and for hypoglycemia when withdrawing them.

Available human studies have not shown a clear major-malformation or miscarriage signal, but the label considers the data insufficient to exclude risk. Poor glucose control itself carries substantial risk. ADA 2026 prefers insulin for type 2 diabetes and gestational diabetes in pregnancy; metformin crosses the placenta and is not a first-line pregnancy agent. Review treatment with the obstetric team.

Milk exposure is low. LactMed reports infant intake generally below 0.5% of the maternal weight-adjusted dose and no adverse effects in one sizeable prospective study; timing feeds around doses adds little benefit. Use extra caution for newborn, premature or renally impaired infants. The label notes limited infant-outcome data; weigh maternal need and infant factors.

Metformin can restore ovulation in some previously anovulatory premenopausal patients, creating a possibility of unintended pregnancy. Discuss contraception and pregnancy intentions.

IR use below age 10 and pediatric use of this ER product are not established. Start cautiously in older adults and check renal function more often. Renal dysfunction increases accumulation; hepatic impairment is a reason to avoid use even though metformin is not hepatically metabolized.

Metformin lowers basal and post-meal glucose through reduced hepatic glucose production and intestinal glucose absorption and improved peripheral insulin sensitivity. It does not increase insulin secretion.

Absorption

IR 500 mg fasting bioavailability approximately 50–60%; ER median peak about 7 hours. Food effects differ by formulation.

Metabolism / distribution

No identified human metabolites; negligible plasma-protein binding and red-cell distribution.

Elimination

Unchanged renal excretion, including tubular secretion; plasma half-life about 6.2 hours and blood half-life about 17.6 hours. Renal impairment prolongs elimination.

• Check glucose control and HbA1c according to the diabetes plan; assess tolerability during titration.
• Obtain eGFR before treatment and at least annually; test more often in older adults or those at risk of renal decline and after relevant acute illness.
• Measure hematologic parameters annually and vitamin B12 every 2–3 years under this label; investigate anemia or neuropathy sooner.
• Review acute illness, dehydration, hypoxia, hepatic disease, alcohol and new interactions; monitor combination-associated hypoglycemia.

• Take with the prescribed meal schedule. ER tablets must remain whole; their inactive shell may appear in stool.
• Report persistent gastrointestinal intolerance. Do not double a missed ER dose.
• Tell procedural teams about metformin before contrast or surgery. Follow a clinician-provided hold/restart plan for restricted intake or acute illness.
• Know lactic-acidosis warning symptoms and seek urgent care. Learn hypoglycemia recognition and treatment when also using insulin or a secretagogue.

Other manufacturers use different imprints; verify packaging with a pharmacist.

Dosage form / strength

Film-coated immediate-release tablet · 500 mg

Label packager

Laurus Labs Limited · Manufactured for Laurus Generics Inc.

Appearance / imprint

White to off-white, round, biconvex · LL

Example package NDC

42385-947-01 · Bottle of 100

Reviewed IR tablets

500, 850 and 1,000 mg.

Reviewed ER tablets

500 mg (LA20) and 750 mg (LA19), white/off-white capsule-shaped tablets.

Other formulations

Other ER products, liquids and combination tablets have independent labels and dosing limits.

Store at 20–25°C; permitted excursions are 15–30°C. Dispense in a light-resistant container. Retain the formulation and strength information and keep medicines away from children.