Metformin
Medically reviewed by the Shrinkopedia editorial team, led by Shariq Refai, MD, MBA, FAPA.
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Metformin is a medication best known for treating type 2 diabetes. In mental health care it is used, beyond its original purpose, to reduce the weight gain and metabolic changes that some antipsychotics cause, especially olanzapine and clozapine. It is taken alongside the antipsychotic, not instead of it, and works best when started early with regular monitoring.
Definition
Metformin is an oral medication in the biguanide class. It lowers blood sugar mainly by reducing how much glucose the liver releases and by improving the body's sensitivity to insulin. In psychiatry, clinicians prescribe it to help prevent or limit antipsychotic-induced weight gain and insulin resistance, a use supported by a 2025 guideline in Schizophrenia Bulletin led by Aoife Carolan.
What it looks like
- Starting metformin at the same time as olanzapine or clozapine to blunt expected weight gain.
- Building the dose up gradually while tracking weight, waist size, and blood tests.
- Continuing the psychiatric medication that is working while metformin manages its metabolic effects.
What people often confuse this with
A treatment for the mental illness itself. Metformin does not treat psychosis, mania, or depression. It addresses a metabolic side effect of some psychiatric medications. The antipsychotic keeps doing the psychiatric work; metformin supports physical health.
Questions people ask
Why is metformin in a mental health encyclopedia?
Because it's frequently used to manage the metabolic side effects of psychiatric medications, particularly antipsychotics. When weight gain and metabolic changes threaten treatment adherence or long-term health, metformin is a common addition.
Does metformin help with weight loss from antipsychotics?
It reduces or reverses some antipsychotic-induced weight gain in trials. Effects are modest but meaningful, and combined with lifestyle interventions, can meaningfully change trajectory.
Is metformin safe?
Generally very well tolerated. Common side effects (GI upset, particularly on starting) usually resolve. Rare but serious concern is lactic acidosis in people with significant kidney dysfunction.
Does it treat depression or anxiety?
No. Metformin isn't a psychiatric medication. Its role in mental health care is metabolic support for people on antipsychotics or with metabolic complications.
Who should get it?
People on antipsychotics with significant weight gain or with metabolic concerns, particularly in shared care with primary care or endocrinology.
What it involves
Metformin is usually started at a low dose and increased slowly to reduce stomach upset. A common pattern is 500 mg once daily, moving to 500 mg twice daily after one week, then increasing every couple of weeks as tolerated toward a typical target around 1000 mg twice daily. It is generally avoided when kidney function is low (eGFR below 30), and kidney function is checked periodically.
Sources
- Carolan A, et al. Metformin for the Prevention of Antipsychotic-Induced Weight Gain: Guideline Development and Consensus Validation. Schizophrenia Bulletin. 2025;51(5):1193-1203.
- FDA prescribing information (label) for metformin, accessed via DailyMed.
- ADA/APA Consensus on Antipsychotic Drugs and Obesity/Diabetes (2004, still foundational; updates via ISBD/EPA metabolic monitoring statements).
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Metformin. Shrinkopedia, medically reviewed by Shariq Refai, MD, MBA. https://shrinkopedia.com/treatments/metformin/- APA
Shrinkopedia. (2026, June 8). Metformin. Medically reviewed by Shariq Refai, MD, MBA. https://shrinkopedia.com/treatments/metformin/- MLA
"Metformin." Shrinkopedia, 8 June 2026, https://shrinkopedia.com/treatments/metformin/.
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