Metformin

ATC code

A10BA02

Therapeutic class

Oral hypoglycemic agent · Biguanide

Forms

oral tablet, film-coated tablet

Brand names

Dianben (ES) · Glucophage (US) · Metformina Merck (ES)

Overall confidence

medium

Regulatory sources consulted

Approved indications

Treatment of type 2 diabetes mellitus, especially in overweight patients, when diet and exercise alone do not result in adequate glycemic control. It may be used as monotherapy or in combination with other oral antidiabetic agents or with insulin.
Polycystic Ovary Syndrome (PCOS), to improve insulin resistance, menstrual regularity, and anovulation. · off-label
Gestational diabetes, as an alternative or adjunct to insulin. · off-label

Contraindications

Absolute

Severe renal impairment (eGFR < 30 ml/min).
Acute metabolic acidosis (e.g., lactic acidosis, diabetic ketoacidosis).
Hepatic impairment, acute alcohol intoxication, alcoholism.
Acute conditions with the potential to alter renal function such as dehydration, severe infection, or shock.

Clinical warnings

Boxed warning · Lactic Acidosis: It is a rare but serious metabolic complication that can occur due to metformin accumulation. The risk increases with renal impairment, advanced age, alcohol consumption, and hypoxic conditions. — AEMPS CIMA

Drug interactions

HighIodinated contrast mediaV08A
Mechanism: Risk of contrast-induced nephropathy, leading to metformin accumulation and lactic acidosis.
Recommendation: Discontinue metformin before or at the time of the procedure. Do not restart until 48 hours after and only if renal function is stable.
AEMPS CIMA
HighAlcoholV03AB16
Mechanism: Increases the risk of lactic acidosis, especially in cases of acute intoxication, fasting, or hepatic insufficiency.
Recommendation: Avoid excessive alcohol intake and acute intoxication.
AEMPS CIMA

Adverse events

Common (≥1%)

nausea · vomiting · diarrhea · abdominal pain · loss of appetite · metallic taste

Rare but serious

lactic acidosis · vitamin B12 deficiency (long-term use) · hepatitis · skin reactions

Pregnancy and lactation

FDA category: B (US FDA classification - historical)

Pregnancy: Uncontrolled diabetes is a risk. Metformin crosses the placenta. Although used in gestational diabetes, insulin is often preferred. Lactation: Excreted in breast milk in small amounts; breastfeeding is not recommended due to limited data and theoretical risk to the infant.

Recent literature (PubMed)

Metformin: Paradigm of therapeutic pleiotropism (1922-2025).
de Leiva Hidalgo A, et al. · Med Clin (Barc) · 2025 · Relevance 5/5
Revisión que actualiza las propiedades farmacológicas, efectos adversos y el pleiotropismo terapéutico de la metformina. Cubre su aplicación en diabetes mellitus, diabetes gestacional, síndrome de ovario poliquístico, regulación del apetito, disbiosis intestinal, protección cardiovascular y renal, y su potencial en fibrosis pulmonar, reducción del riesgo de neoplasias y longevidad.
Pleiotropic Effects of Metformin in Osteoarthritis.
Lambova SN · Life (Basel) · 2023 · Relevance 4/5
Analiza los efectos pleiotrópicos potenciales de la metformina en la osteoartritis (OA), especialmente en el fenotipo de OA metabólica. La metformina podría ralentizar la progresión de la OA al modular la inflamación, el estrés oxidativo, la autofagia, los niveles de adipoquinas y el microbioma.
Recommendations of the Spanish Society of Endocrinology and Nutrition (SEEN) on "what not to do" in clinical practice.
Díez JJ, et al. · Endocrinol Diabetes Nutr (Engl Ed) · 2025 · Relevance 2/5
La Sociedad Española de Endocrinología y Nutrición (SEEN) compila una serie de recomendaciones de 'no hacer' en diversas áreas, incluyendo diabetes, para promover una atención médica basada en la evidencia y coste-efectiva, evitando el sobreuso de procedimientos no probados.