Although modest reversal of clozapine-associated weight gain is found with metformin, primary prevention of weight gain is more valuable. Use with insulin
Metformin may reduce the insulin requirement in type 1 diabetes, albeit with an increased risk of hypoglycemia. Life extension
There is some evidence metformin may be helpful in extending lifespan, even in otherwise healthy people. It has received substantial interest as an agent that delays aging, possibly through similar mechanisms as its treatment of diabetes (insulin and carbohydrate regulation). This is controversial, and an area of active research. Alzheimers disease
The possibility that metformin can delay the onset or progression of Alzheimers, or even prevent it, is under investigation. There has been a variety of research published in this field in an effort to establish a correlation between type 2 diabetes and Alzheimers disease. Research now includes studies with participants not diagnosed with diabetes. Contraindications
Metformin is contraindicated in people with:

Severe renal impairment (estimated glomerular filtration rate (eGFR) below 30 mL/min/1.73 m2)
Known hypersensitivity to metformin
Acute or chronic metabolic acidosis, including diabetic ketoacidosis (from uncontrolled diabetes), with or without comaWarnings are also given regarding the use of metformin in less severe renal impairment, people aged 65 years old or greater,  hypoxic states (e.g., acute congestive heart failure), excessive alcohol intake, hepatic impairment, concomitant use of certain drugs (e.g.
This includes in those who have not been able to get pregnant with clomiphene. Metformin does not appear to change the risk of miscarriage. A number of other benefits have also been found both during pregnancy and in nonpregnant women with PCOS. In an updated Cochrane (2020) review on metformin versus placebo/no treatment before or during IVF/ICSI in women with PCOS no conclusive evidence of improved live birth rates was found. In long GnRH-agonist protocols there was uncertainty in the evidence of improved live birth rates but there could be increases in clinical pregnancy rate. In short GnRH-antagonist protocols metformin may reduce live birth rates with uncertainty on its effect on clinical pregnancy rate. Metformin may result in a reduction of OHSS but could come with a greater frequency of side effects. There was uncertainty as to metformins impact on miscarriage. The evidence does not support general use during pregnancy for improving maternal and infant outcomes in obese women.The United Kingdoms National Institute for Health and Clinical Excellence recommended in 2004 that women with PCOS and a body mass index above 25 be given metformin for anovulation and infertility when other therapies fail to produce results. UK and international clinical practice guidelines do not recommend metformin as a first-line treatment or do not recommend it at all, except for women with glucose intolerance. The guidelines suggest clomiphene as the first medication option and emphasize lifestyle modification independently from medical treatment.