Can metformin cause sexual side effects such as decreased libido or erectile dysfunction?

Short answer

Metformin itself is not commonly linked to sexual side effects, and evidence suggests it may improve erectile function in certain men with insulin resistance. However, some official patient information materials list “decreased sexual ability” among possible issues seen with diabetes complications rather than as a direct, common effect of metformin. ^{[1] [2]} In specific situations (for example, women with high androgen levels), metformin can lower testosterone, which could theoretically affect libido, but this is not a typical complaint in routine metformin use. ^{[3] [4]}

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What official sources say

• Some consumer drug information pages mention “decreased sexual ability in men and women” when discussing diabetes-related complications in general care with metformin therapy; this phrasing reflects problems tied to diabetes itself (nerve and vascular damage), not a well-established, frequent adverse effect uniquely caused by metformin. ^{[1] [2]}
• Standard metformin labels and summaries focus on gastrointestinal side effects, vitamin B12 lowering, and hypoglycemia risk when combined with other drugs; they do not highlight sexual dysfunction as a common or expected adverse reaction. ^{[5] [6]}

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Clinical research in men

• In a randomized, double‑blind pilot study of eugonadal nondiabetic men with insulin resistance and poor response to sildenafil, adding metformin improved erectile function scores over 2–4 months, while reducing insulin resistance. Adverse events were mainly mild gastrointestinal issues. This suggests metformin may enhance erectile function in the context of insulin resistance rather than impair it. ^{[7] [8] [9] [10]}

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Clinical research in women

• Metformin can lower circulating androgens (like total testosterone) and raise sex hormone–binding globulin in women, particularly in conditions such as polycystic ovary syndrome; these hormonal changes can be beneficial for metabolic and reproductive health but could, in theory, influence libido in some individuals due to lower free androgens. The overall quality of evidence varies, and libido impact is not consistently measured. ^[4]
• In postmenopausal women with insulin resistance, metformin reduced free and total testosterone compared to placebo, with improved insulin sensitivity; sex hormone–binding globulin did not change. This demonstrates a causal link between insulin resistance and testosterone production, but it does not directly establish metformin as a cause of low libido in typical use. ^{[3] [11] [12] [13]}

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Distinguishing diabetes effects from drug effects

• Diabetes itself is a major risk factor for erectile dysfunction due to vascular and nerve damage and endothelial dysfunction; rates can be high and increase with age. Improved glycemic control and insulin sensitivity generally support sexual function. ^[14]
• When metformin helps reduce insulin resistance and stabilize blood sugar, it may indirectly improve endothelial function and nitric oxide availability, supporting better erectile responses, especially when combined with therapies like sildenafil. ^{[7] [8]}

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Safety profile and common side effects

• Real‑world and trial data consistently show metformin’s most common side effects are gastrointestinal (nausea, diarrhea, abdominal discomfort), with possible vitamin B12 lowering over time; sexual dysfunction is not a typical signal in safety summaries. ^{[15] [5] [6]}
• Metformin does not increase lactic acidosis risk compared with other glucose‑lowering therapies in modern analyses; sexual side effects are not highlighted as a concern in these assessments. ^[16]

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Practical takeaways

• For most users, metformin is unlikely to directly cause decreased libido or erectile dysfunction; if sexual symptoms occur, it is often worthwhile to consider diabetes control, other medications (e.g., SSRIs, beta‑blockers), depression, sleep problems, cardiovascular risk, thyroid disease, and vitamin deficiencies.
• In men with insulin resistance, metformin may actually improve erectile function, especially alongside PDE‑5 inhibitors like sildenafil. ^{[7] [8]}
• In women prone to higher androgens, metformin’s reduction in testosterone may be beneficial for metabolic and reproductive outcomes; any impact on libido is variable and not well established in trials. ^{[4] [3]}

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What you can do

• If you notice changes in sexual desire or erectile performance after starting metformin, it could be multifactorial rather than a direct drug effect; checking blood sugar control, cardiovascular risks, mood, sleep, endocrine status, and vitamin B12 can be helpful. ^{[5] [6]}
• Address modifiable factors: regular exercise, weight management, smoking cessation, alcohol moderation, stress reduction, and sleep optimization can support sexual health and insulin sensitivity.
• Discuss medication timing, dose, and any gastrointestinal side effects with your clinician, as improving tolerability may also improve overall wellbeing and sexual function. ^{[5] [6]}

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Bottom line

Metformin is not commonly associated with sexual side effects, and in some insulin‑resistant men it can improve erectile function; sexual problems in people with diabetes are more often due to the disease and other factors than to metformin itself. ^{[7] [8] [14]} Official consumer drug information that mentions decreased sexual ability typically references diabetes complications rather than a direct adverse effect from metformin. ^{[1] [2]}