Combination of Myo-inositol and D-chiro-inositol: A First-Line Treatment for PCOS

Inositols have been suggested as a first-line treatment for PCOS. Have you heard about the numerous benefits of inositols for PCOS but not sure what kind to take? This article summarizes the differences between the two main types of inositols, MYO and d-chiro inositol (DCI) including what they are and what they do, their benefits, and any potential side effects to look for.

What are Inositols?

Inositols are relatives of the B-vitamins and a component of the cell membrane. Inositols are found in fruits, beans, grains, and nuts and is also made by the body. While there are nine forms of inositol, myo (MYO) and d-chiro-inositol (DCI) types have been well studied in women with PCOS, both showing good results in regards to improving both metabolic and reproductive aspects.

MYO and DCI: Secondary Messengers

MYO and DCI are separate molecules that work differently in the body. It’s believed that women with PCOS may have a defect in the insulin receptor’s  secondary messengers contributing to insulin resistance and infertility. MYO and DCI work as these secondary messengers. Simply put: when we eat foods (mostly carbohydrates), they get converted into glucose in our blood stream. We need the glucose to enter our cells to be used for energy. When blood glucose levels rise, insulin is released. Insulin then binds to a receptor on the cell’s surface, causing secondary messengers to be released. These messengers send a signal (imagine a doorbell is rung) telling the cell to open the door and let glucose in. However, with PCOS, the doorbell  may be defective. This means that it takes longer for the cells to open its doors to glucose resulting in higher amounts of insulin needing to be secreted. Inositols work as secondary messengers to repair the doorbell so that the cell doors open in correct response to glucose, resulting in less insulin needing to be secreted. See video below for more detailed explanation.

Why the 40:1 Ratio of Myo to DCI Matters

The majority of the tissues in our bodies have a unique combination of MYO to DCI in a 40:1 ratio. MYO converts into DCI but in PCOS women, this conversion is believed to be defective. So, what happens in PCOS women is that MYO is get converted into DCI too quickly, depleting levels of MYO inositol and raising levels of DCI. This is why so many women with PCOS struggle with infertility because they are making too much DCI which worsens egg quality in high amounts (over 600 mg per day). This is why taking a combination of MYO and DCI in the 40:1 ratio to maintain the physiological ratio in the body is important.

Health Benefits of Myo and DCI Inositol

Myo and d-Chiro Inositol Combined

New research has shown that a combination of MYO and DCI in the 40:1 ratio is a more effective approach for treating PCOS than taking MYO or DCI alone in regards to improving metabolic aspects and for improving egg quality and menstrual regulation.

Nordio and colleagues compared the effectiveness of MYO and DCI combined in a physiological ratio (40:1) with MYO. In that study, it was found that a combined therapy was able to restore the hormonal and metabolic parameters earlier than when the patients were treated with MYO alone, with significant changes evident in the metabolic profile between the MYO and MYO and DCI groups.

They concluded that “the combined administration of MYO and DCI in a physiological plasma ratio (40:1) should be considered as the first line of approach in overweight patients with PCOS,”

In their randomized trial, Benelli and colleagues saw a statistically significant reduction of LH, free testosterone, fasting insulin, and HOMA index only in the group of young PCOS women treated with the combined therapy of MYO plus DCI.

Not only can a combined treatment of MYO and DCI help to improve metabolic aspects and fertility, but also helps with improved egg quality and IVF outcomes. In their randomized controlled study, Colazingari and colleagues found that found that only the combined therapy was able to improve oocyte and embryo quality, as well as pregnancy rates, in women with PCOS who were undergoing IVF.

Brusco and colleagues also showed that the combination of MYO and DCI significantly improved the overall egg quality and consequently embryo development.


How Much to Take?

It’s recommended that women with PCOS take a combined amount of MYO (2 to 4 grams) and DCI (50 to 100 mg) daily in the ideal physiologic ratio of 40:1. Ovasitol is what I recommend because it has passed the rigorous 3rd party testing to have the NSF certification. It’s also a tasteless and convenient powder (no more pills to swallow!)

READ I Took Ovasitol. Here’s What Happened

READ 10 Surprising Benefits of Ovasitol for PCOS

READ Ovasitol Frequently Asked Questions

Will Ovasitol Negatively Affect the Quality of My Eggs?

No. There is no research to show the combined amount of inositol in Ovasitol will negatively affect egg quality. There is research to show that egg quality worsens when women with PCOS take very high amounts of DCI (600mg or more daily). Ovasitol has only 50 mg of DCI per dose.  If anything, studies (see above) have shown that the unique 40:1 ratio of MYO to DCI actually improves egg quality better than MYO alone.

Side Effects

Generally, MYO and DCI are well tolerated but may cause low blood sugar, especially if taking medications or other supplements that lower blood sugar. MYO and DCI are safe to take during pregnancy. As always, check with your physician before starting inositol or any supplement.

angela grassi PCOS dietiitian nutritionistAngela Grassi, MS, RDN, LDN, is the founder of The PCOS Nutrition Center, for which she has been providing evidence-based nutrition information and coaching to people with PCOS for over 20 years. Angela is the author of several books on PCOS, including PCOS: The Dietitian’s Guide, The PCOS Workbook: Your Guide to Complete Physical and Emotional Health, and The PCOS Nutrition Center Cookbook. Angela is the past recipient of The Outstanding Nutrition Entrepreneur Award, The Award in Excellence in Practice in Women’s Health, and The Award for Excellence in Graduate Research, from the Academy of Nutrition and Dietetics. Having PCOS herself, Angela has been dedicated to advocacy, education, and research of the syndrome. Click here to schedule a session with Angela to learn more about how nutrition coaching for PCOS can help you!


Nordio M, Proietti E. The combined therapy with myo-inositol and D-chiro-inositol reduces the risk of metabolic disease in PCOS overweight patients compared to myo-inositol supplementation alone. Eur Rev Med Pharmacol Sci. 2012; 16(5): 575–581.

Dinicola S. The rationale of the myo-inositol and D-chiro-inositol combined treatment for polycystic ovary syndrome. J Clin Pharmacol. 2014 Oct;54(10):1079-92.

Benelli, E. A Combined Therapy with Myo-Inositol and D-Chiro-Inositol Improves Endocrine Parameters and Insulin Resistance in PCOS Young Overweight Women.Int J Endocrinol. 2016;Int J Endocrinol. 2016
Colazingari S, Treglia M, Najjar R, Bevilacqua A. The combined therapy myo-inositol plus D-chiro-inositol, rather than D-chiro-inositol, is able to improve IVF outcomes: results from a randomized controlled trial. Arch Gynecol Obstet. 2013 Dec;288(6):1405-11.

Brusco GF, Mariani M. Inositol: effects on oocyte quality in patients undergoing ICSI. An open study. Eur Rev Med Pharmacol Sci. 2013; 17(22): 3095–3102.

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Comments (14)
  • Marg

    April 27, 2015 at 9:31 am

    Thank you! I often wake with a dry/sore throat & my husband has had to wake me before due to snoring/stop breathing….ill certainly take a trip to my gp to get me a CPAP machine.

  • Dina

    November 27, 2015 at 9:31 am

    This is a really helpful post. Who knew that these symptoms could also be associated with PCOS? This site is really helpful. Can obstructive sleep apnea be minimized with weight loss?

  • Odalys

    March 6, 2016 at 9:30 pm

    Another reason to love coffee! #coffeelover ☕

  • Tarun Khurana

    March 31, 2016 at 5:26 am

    My wife is suffering form PCOS, I juts see the website & find inositol is helpful in PCOS, she is suffering from weight gain problem.
    I checked with your website that product OVASITOL powder is very helpful.
    Please conform how we can we purchase this product in India as your website says cannot shipped out of USA & canada..
    Please help us .

  • dr s j taye

    April 7, 2016 at 9:05 am

    Vvery informative,effective .

  • Jill Meadows

    August 1, 2017 at 1:33 pm

    My daughter, 16 years old, has Secondary Ammenorhea. She got her period once. She also has high levels of Testosterone and her female doctor would like her to go on progesterone to see if it would make her bleed and then birth control pills. We have not done that but tried natural supplements, like Blue Cohosh, Vitex, digestive enzymes, good diet. She still has the signs of PCOS with extra hair, acne, poor digestion, tired, no menstrual cycle. What would you recommend?

  • Angela Grassi

    August 1, 2017 at 2:16 pm

    Ovasitol can be an option for her. Sounds like there are many things going on. Perhaps nutrition coaching with us or other dietitian in your area that specializes in PCOS would help? You can contact us for more info at

  • alam zaidi

    January 24, 2018 at 1:55 am

    its nice ,informative article thanks

  • Sheila

    June 16, 2018 at 10:56 pm

    Is any one get pregnant off these pills?

  • Angela Grassi

    June 17, 2018 at 6:03 am

    Ovasitol can improve egg quality and ovulation increasing the chances of conception.

  • Genesis Tentler

    January 24, 2019 at 3:03 pm

    Wondering if it safe to take Oviastol if one consumes occasional alcohol? I’m a social drinker that enjoys craft brews and bourbon. Just curious if there were side effects at all while regularly taking Oviastol.
    Thank you

  • Angela Grassi

    January 24, 2019 at 3:22 pm

    yes, occasional alcohol use is fine.

  • Tyler

    February 26, 2020 at 4:07 pm

    Thank you so much for actually including your sources of information. Not only do I know that you’re not just talking out of your butt, but I can actually look at the research on PCOS. As I’m sure you know, it’s not easy to find substantial research being done on PCOS in particular, so I really appreciate that you are providing those resources for your readers.
    I’m actually trying to find sources to write a research grant about possible intestinal microbial links with PCOS symptoms, and I thought why not see if your blog had any reputable sources. I was pleasantly surprised that you had a list, so thank you. If you have any journal articles up your sleeve that are remotely related, please send them my way!

  • Leah Cowles

    May 1, 2021 at 3:39 pm

    I’m in my 40s, newly diagnosed. How long before I see weight loss? I packed on 25 lbs in 6 months. Exercise did nothing.

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