Myo-inositol vs. Metformin for PCOS

One of the primary drivers identified in Polycystic Ovarian Syndrome (PCOS) is insulin. Women with PCOS have an exaggerated insulin release in response to dietary sugar intake, and develop insulin resistance over time. This increased insulin is one of the main drivers of the following PCOS symptoms:

  • long menstrual cycles
  • hair loss
  • excessive facial or body hair growth
  • acne
  • difficulty conceiving.

Addressing insulin resistance is absolutely essential in PCOS treatment. The first step is to take a deep dive into diet and remove foods that drive insulin and blood sugar. In addition to dietary changes, there are medications and supplements that can be used to further reduce insulin. The most common medication prescribed to women with PCOS to control insulin is metformin, and the most common naturopathic prescription is myo-inositol.

But how do these two compare? Which is more effective?
Luckily, a lot of research has been done comparing these two options head to head!


Metformin is a prescription medication and is one of the most studied treatment options for PCOS1. It works by reducing sugar absorption by the gastrointestinal tract, and also reduces the body’s sugar production and release. In addition, it enhances peripheral insulin sensitivity1.

For this reason, metformin is one of the most common treatment options for type 2 diabetes, but it also makes it an effective treatment option for PCOS 1.

Unfortunately, many individuals find metformin treatment intolerable due to a high rate of gastrointestinal side effects2.

Thankfully, there’s another option!


Metformin vs Myo-inositol

Myo-inositol is considered to be a part of the vitamin B complex family and sensitizes cells to insulin1. Women with PCOS have been found to have deficiencies in this vitamin, which may contribute to its efficacy.

Studies have found that myo-inositol enhances ovulation, decreases testosterone, and can help restore both the hormonal and metabolic imbalances found in women with PCOS1.

Metformin vs. Myo-inositol

A meta-analysis compiled all of the trials run from 1994 to 2007, which looked at how metformin and myo-inositol compared.

It concluded that they were equally effective at the following:

The authors noted that ‘There was strong evidence of an increased risk of adverse events among women receiving metformin compared to those receiving myo-inositol 2.

Another study found that a combination of myo-inositol and d-chiro-inositol were more effective in the following outcomes than metformin:

    • menstrual cycle regulation
    • hirsutism score
    • fasting and post-prandial glucose and insulin levels
    • serum DHEA levels
    • serum free testosterone
    • day 3 LH and FSH ratio3

Myo-inositol seems to be as effective as metformin, and may even be more effective for the treatment of PCOS. Considering its strong safety profile, myo-inositol may be a preferred treatment option.  We use this quite frequently to treat PCOS naturally in our Toronto clinic.

There’s also some evidence that using the two treatments in tandem may be even more effective. One study looked at the use of metformin only compared to a combination of metformin and myo-inositol in PCOS women undergoing ovulation induction cycles4. It found that the live birth rate was higher in women in the combined treatment group compared to metformin alone4.

Key Takeaways

  • Exaggerated insulin release and insulin resistance is one of the main drivers of PCOS
  • Metformin is the top medication prescribed to women with PCOS to control insulin levels, and myo-inositol is the top naturopathic prescription
  • Metformin and myo-inositol have been found in research to be equally effective at improving insulin levels, testosterone levels, and reducing BMI
  • Metformin is associated with a high rate of gastrointestinal side effects whereas myo-inositol is not
  • A combination of metformin and myo-inositol may be more effective in women undergoing ovulation induction cycles