Best Myo-Inositol Supplement (2026): Label Servings, the 40:1 Ratio & Research
By Erin Rose Updated October 13, 2026 How we score
Ovasitol is the best myo-inositol for most people. It is on NSF/ANSI 173, and two scoops give 4 g a day, the amount many trials used, for $0.96 a day at list price. Want capsules? Buy Wholesome Story. Want the lowest cost? Micro Ingredients, but no public list checks it.
We earn a commission if you buy through our links. It never changes a score or a pick. How we make money
Our picks at a glance
Best overall
Ovasitol Inositol Powder
8.0/10 Our score
8.0/10, the top score of the 3 on a public testing list (tied with Wholesome Story, and cheaper a day)
- Myo-inositol
- 2 g a scoopplus 50 mg D-chiro-inositol (40:1)
- For 4 g a day
- 2 scoops$0.96 a day at list price
- Testing list
- NSF/ANSI 173Checked October 13, 2026
- Label
- 4 g a dayOne scoop in the morning, one at night
- Tub
- 180-serving tub, $86.68brand list price; 90 days at two scoops
Our take
Why we pick it It is on NSF/ANSI 173, a list that checks the label is accurate and that contaminants stay under set limits. Its own label says 4 g a day, the amount many trials used, so you don’t have to double up. Of the two tested 40:1 products, it costs less a day.
What you give up It costs 2.1 times as much a day as Micro Ingredients, which has the same amounts a scoop. Each scoop also has 50 mg of D-chiro-inositol. That is not why we pick it: the evidence for the ratio is thin.
The label
Testing record
- NSF/ANSI 173: contents match the label Checked October 13, 2026.
Not found on: NSF Certified for Sport, Informed Sport, Informed Choice, USP Verified.
Our other 3 picks
Each is for a different need: capsules, or the lowest cost.
Capsules
Wholesome Story Myo & D-Chiro Inositol
8.0/10 Our score
8.0/10, tied for #2 of the 9 myo-inositol products we score
- Myo-inositol
- 2 g in 4 capsulesplus 50 mg D-chiro-inositol (40:1)
- For 4 g a day
- 8 capsules$1.86 a day at list price
- Testing list
- NSF/ANSI 173Checked October 13, 2026
- Label
- 2 g a dayNIH label: 4 capsules a day
Our take
Why it is here If you would rather swallow capsules, it is the tested choice. It is also on NSF/ANSI 173. 4 g takes 8 capsules, at $1.86 a day, about 1.9 times our pick.
What to know Its 2023 NIH label says 4 capsules a day, which is 2 g. The brand’s page now says 4 to 8, and NSF’s listing gives 8.
The label
Testing record
- NSF/ANSI 173: contents match the label Checked October 13, 2026.
Not found on: NSF Certified for Sport, Informed Sport, Informed Choice, USP Verified.
Lowest cost 40:1
Micro Ingredients Myo & D-Chiro Inositol Powder
8.5/10 Our score
8.5/10, the top score of the 9 myo-inositol products we score
- Myo-inositol
- 2 g a scoopplus 50 mg D-chiro-inositol (40:1), per the brand’s page
- For 4 g a day
- 2 scoops$0.45 a day at list price
- Testing list
- None foundIts store says “3rd party lab tested” and names no lab
- Label
- Not in NIH’s databaseAmounts from the brand’s own page
Our take
Why it is here It is the cheapest 40:1 powder we price, $0.45 a day for 4 g. It has the top score of the 9, 8.5/10, because it costs least.
What to know You can’t check it. It is on none of the five public lists we search, and NIH has no record of its label. If price matters most and you trust the brand, it is a fair buy. Why it is not our pick.
Testing record
Not found on any testing list we check.
Not found on: NSF Certified for Sport, Informed Sport, Informed Choice, NSF/ANSI 173, USP Verified.
Lowest cost plain
- Myo-inositol
- 1 g a scoopNo D-chiro-inositol
- For 4 g a day
- 4 scoops$0.26 a day at list price
- Testing list
- None foundIts store says “Tested by Independent, ISO-Accredited Laboratories”
- Label
- 1 g a dayNIH label 306234
Our take
Why it is here Plain myo-inositol is what many trials used, and this is the lowest cost of all we price: $0.26 a day for 4 g.
What to know Its label says 1 g a day, so 4 g is 4 scoops. Its store names no lab, and no public list names it.
Testing record
Not found on any testing list we check.
Not found on: NSF Certified for Sport, Informed Sport, Informed Choice, NSF/ANSI 173, USP Verified.
Which one is for you?
| Your situation | What to buy |
|---|---|
| You want a tested product whose label gives 4 g a day | Ovasitol, $0.96 a day (our pick) |
| You would rather swallow capsules | Wholesome Story: 8 capsules for 4 g, $1.86 a day (details) |
| You want the cheapest 40:1 powder | Micro Ingredients, $0.45 a day. No public list checks it (why that matters) |
| You want plain myo-inositol at the lowest cost | Nutricost, $0.26 a day: 4 scoops for 4 g (details) |
| You compete in a drug-tested sport | Momentous Inositol is on NSF Certified for Sport. It has 0.9 g in 2 capsules, so 4 g costs $2.22 a day |
| You already have a myo-inositol | Finish it. Follow the serving on your label. |
| You are pregnant, trying to get pregnant, or take a prescription medicine | Ask your doctor first. What to check |
NSF’s list for our two tested 40:1 picks
Ovasitol: NSF/ANSI 173
Wholesome Story: NSF/ANSI 173
Why isn’t Micro Ingredients our pick?
Because you can’t check it. It has the top score, 8.5/10, because it costs least: $0.45 a day for 4 g. But:
- Testing. Its store says “3rd party lab tested,” but it names no lab, and it is on none of the five public lists we search.
- Label. NIH’s label database has no record of it. Its amounts come from the brand’s own page.
We pick a product someone outside the brand checks. Over a year at 4 g a day, that costs $352 for Ovasitol against $165 for Micro Ingredients. If price matters most to you, Micro Ingredients is a fair buy. Ovasitol vs Micro Ingredients, side by side.
| Item | Value |
|---|---|
| Nutricost Myo-Inositol Powder | $0.26 |
| Micro Ingredients Myo & D-Chiro Inositol Powder | $0.45 |
| Zazzee Pregnositol Powder | $0.66 |
| Pure Encapsulations Inositol Powder | $0.90 |
| Ovasitol Inositol Powder | $0.96 |
| Jarrow Formulas Inositol 750 mg | $1.01 |
| Fairhaven Health Myo & D-Chiro Inositol | $1.67 |
| Wholesome Story Myo & D-Chiro Inositol | $1.86 |
| Momentous Inositol | $2.22 |
All 14 we checked
We scored 9 and could not score 5. Blends are scored against blends and plain myo-inositol against plain, because part of a blend’s price is the D-chiro-inositol.
| Product | Score | Myo-inositol | 4 g a day | Testing list | Pack and list price | Buy |
|---|---|---|---|---|---|---|
| 40:1 blends (with D-chiro-inositol) 5 scored | ||||||
| Micro Ingredients Myo & D-Chiro Inositol PowderMicro Ingredients | 8.5/10 | 2 g1 scoop (2.05 g) | $0.452 scoops | None found | 1 lb tub, $49.95list price at Micro Ingredients’s own store | Check price on Amazon |
| Ovasitol Inositol PowderTheralogix | 8.0/10 | 2 g1 scoop (2.4 g) | $0.962 scoops | NSF/ANSI 173 | 180-serving tub, $86.68list price at Theralogix’s own store | Check price on Amazon |
| Wholesome Story Myo & D-Chiro InositolWholesome Story | 8.0/10 | 2 g4 capsules | $1.868 capsules | NSF/ANSI 173 | 120-capsule bottle, $27.95list price at Wholesome Story’s own store | Check price on Amazon |
| Zazzee Pregnositol PowderZazzee | 6.0/10 | 2 g1 scoop (2.14 g) | $0.662 scoops | None found | 183-serving tub, $59.97list price at Zazzee’s own store | Check price on Amazon |
| Fairhaven Health Myo & D-Chiro InositolFairhaven | 5.0/10 | 2 g4 capsules | $1.678 capsules | None found | 120-count bottle, $24.99list price at Fairhaven’s own store | Check price on Amazon |
| Plain myo-inositol 4 scored | ||||||
| Nutricost Myo-Inositol PowderNutricost | 7.0/10 | 1 g1 scoop (1 g) | $0.264 scoops | None found | 1 lb tub, $29.97list price at Nutricost’s own store | Check price on Amazon |
| Pure Encapsulations Inositol PowderPure Encapsulations | 5.0/10 | 4 g1 scoop (4.2 g) | $0.901 scoop | None found | 8.8 oz tub, $54.00list price at Pure Encapsulations’s own store | Check price on Amazon |
| Momentous InositolMomentous | 5.0/10 | 0.9 g2 capsules | $2.228 to 9 capsules | NSF Certified for Sport, NSF/ANSI 173 | 2-capsule bottle, $29.99list price at Momentous’s own store | Check price on Amazon |
| Jarrow Formulas Inositol 750 mgJarrow | 2.0/10 | 0.75 g1 capsule | $1.015 to 6 capsules | None found | 100-capsule bottle, $18.99list price at Jarrow’s own store | Check price on Amazon |
None found: not on the NSF, USP or Informed lists, searched October 13, 2026 (USP: September 22, 2026).
How we score, and the 5 we could not score
The score. Five marks, 10 points in all. Does a serving give at least 2 g of myo-inositol (the low end of the amounts studied)? Is the product on a public testing list? What does 4 g a day cost against the cheapest of its kind? Does the label state the amounts? Has FDA recalled anything from the brand? Dose and testing are worth up to 3 points each, cost up to 2, label and recalls up to 1 each. A brand’s own “tested” claim earns half the testing points. How we score.
Label amounts. 6 of the 8 labels we could read direct less than 4 g a day; Jarrow 750 mg’s says 0.75 g. So we price every product at 4 g a day.
Not scored (5).
- Double Wood Inositol 1,000 mg: Its NIH label (315653) says "Do not exceed 4 softgels per day", which is 2 g; the 4 g trial dose would break its own warning, so we do not price it per 4 g.
- Pregnitude Myo-Inositol + Folic Acid: No list price we can cite: Exeltis sells Pregnitude through retailers only, and we do not use Amazon prices.
- NOW Foods Inositol 500 mg: No list price we can cite: NOW sells through retailers only, and we do not use Amazon prices.
- Life Extension Inositol 1,000 mg: No list price we can cite for this size (checked September 29, 2026); we do not use Amazon prices.
- Designs for Health Sensitol: Its label gives 1.6 g of myo- and D-chiro-inositol combined, not the myo-inositol alone, so we cannot price it per 4 g of myo-inositol.
Where we disagree with the big guides
Two of the top search results for “best myo-inositol supplement” are guides that pick products. We read both on September 30, 2026. Both lean on the 40:1 ratio more than the trials do.
Innerbody (updated July 30, 2026) names four picks. We agree on one: its 40:1 pick is the same Wholesome Story capsules as our capsule pick. But it calls the 40:1 ratio ideal, and the trials behind that are small. Its general pick, Life Extension Inositol Caps, gives 1 g a capsule, so 4 g takes 4 capsules. Innerbody says it is made in “NSF-registered” facilities. That checks the factory. It does not put the product on NSF’s list. We could not score it: we found no list price we can cite.
Feed Your Zest, a dietitian practice’s blog (February 26, 2025), picks Ovasitol, as we do. It calls Ovasitol “the only 40:1 inositol supplement independently tested and certified by NSF® International.” That is not true now: Wholesome Story is on NSF/ANSI 173 too (checked October 13, 2026).
What the research says
This is research, not advice for any condition. We report what the studies found and who ran them. Nothing here is a reason to buy a product.
Not much is proven. The review behind a 2023 international guideline looked at 30 trials and called the evidence “limited and inconclusive” (Fitz 2024). Since 2023, journals have retracted 11 inositol papers and flagged 7 more with an expression of concern. 7 of those 18 papers list one researcher, Vittorio Unfer, as an author. Two older reviews we cite pooled papers that were later retracted: Unfer 2017 did, and Pundir 2018 likely did. The 2024 guideline review did not. More on the research.
Does the 40:1 ratio matter?
Probably not much. 40:1 means 40 parts myo-inositol to 1 part D-chiro-inositol. The 40:1 ratio is common, but it rests on two small trials by one author. One trial had 50 women and no placebo group; the 40:1 mix did better on some lab measures at three months, but not at six (Nordio 2012). The other spread 56 women across seven ratios, 8 women each (Nordio 2019). No large trial shows it beats plain myo-inositol. The ratio, in detail.
Frequently asked questions
What has myo-inositol been studied for?
This is research, not advice for any condition. Most trials were small, and many were in women with PCOS. Others were in pregnancy. The review behind the 2023 international guideline looked at 30 trials and called the evidence limited and inconclusive (Fitz 2024). A large 2025 trial in pregnant women found no difference from a placebo (van der Wel 2025). The research
What's the 40:1 ratio?
It means 40 parts myo-inositol to 1 part D-chiro-inositol, a related compound: 2 g of myo-inositol with 50 mg of D-chiro-inositol. The 40:1 ratio is common, but it rests on two small trials by one author. No large trial shows that a 40:1 blend beats plain myo-inositol. The ratio, in detail
How do I take it?
Follow the serving on your label. Many trials used 4 g of myo-inositol a day, often 2 g twice a day. No guideline names a dose. Don’t take more than 4 g a day unless your doctor says so. Servings for each product
Are there side effects?
In trials at 2 to 4 g a day, side effects were mild stomach upset at most (Fitz 2024). Ask your doctor first if you are pregnant or trying to get pregnant, if you take lithium or valproate, or if you take a prescription medicine such as metformin or another diabetes medicine. Before you take it
More: myo-inositol guide, third-party tested myo-inositol, every size, priced and Ovasitol vs Micro Ingredients.
Sources
- Fitz V, et al. Inositol for polycystic ovary syndrome: a systematic review and meta-analysis to inform the 2023 update of the International Evidence-based PCOS Guidelines. J Clin Endocrinol Metab. 2024;109(6):1630-1655. PubMed 38163998
- van der Wel AWT, et al. Myo-inositol supplementation to prevent pregnancy complications in polycystic ovary syndrome: a randomized clinical trial. JAMA. 2025;334(13):1151-1159. PubMed 40920401
- Unfer V, et al. Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials. Endocr Connect. 2017;6(8):647-658. PubMed 29042448. Pundir J, et al. Inositol treatment of anovulation in women with polycystic ovary syndrome: a meta-analysis of randomised trials. BJOG. 2018;125(3):299-308. PubMed 28544572
- Nordio M, Proietti E. Eur Rev Med Pharmacol Sci. 2012;16(5):575-81. PubMed 22774396. Nordio M, et al. Eur Rev Med Pharmacol Sci. 2019;23(12):5512-5521. PubMed 31298405
- Retractions and expressions of concern since 2023: 18 notices, listed on the myo-inositol guide. Searched October 13, 2026.
- Other guides, read September 30, 2026: Innerbody, Best Inositol Supplements and Feed Your Zest, Choosing the Best Inositol Supplement.
- Labels: NIH Dietary Supplement Label Database and brand pages. Testing: NSF/ANSI 173, NSF Certified for Sport, Informed Sport and Informed Choice, searched October 13, 2026; USP Verified, September 22, 2026. Recalls: openFDA. Prices: each brand’s own list price, checked October 13, 2026.
Scores updated October 13, 2026. Myo-inositol per serving comes from each label; D-chiro-inositol is not counted.