Third-Party Tested Inositol 2026: Which Are NSF Certified
Not medical advice. This page checks products against public certification registries and the brands’ own published lab reports; it does not test products itself.
Quick answer
“Third-party tested” is four different things, and only the top two can be checked; the cheapest certified 4 g here costs $1.53. Of the 3 myo-inositol products we track, 2 are in an independent certification registry (0 of them NSF Certified for Sport, 0 Informed Sport), 0 publish a lot-specific lab report without a registry listing, 0 show a report you cannot match to your bottle, and 1 has nothing we could check.
Cheapest certified: Wholesome Story Myo-Inositol & D-Chiro Inositol 40:1, $1.53 per 4 g, listed in the NSF/ANSI 173 registry as “Myo & D-Chiro Inositol”. See every product on the ladder →
Every myo-inositol product we track, on the verification ladder
Original research3 myo-inositol products checked, one by one, against the NSF/ANSI 173 finished-product registry (3,053 listings, snapshot 2026-08-25), the USP Verified list (159 products) and the Informed Sport / Informed Choice database (2,105 products), then each brand’s own site for a published certificate of analysis (2026-09-19). A match means the exact product and form, never the brand alone.
Method: the roster is every product in our catalog for this category with a live Amazon offer. Registry matches are exact-product matches (name, form and, where the registry lists it, flavour) against our snapshots, never a brand-level match; the certificate check read each brand’s own site for a published, lot-specific certificate of analysis. A product whose brand site blocked the check is recorded as unverified, not as failing. Cost is computed from the current Amazon price of the exact container and the dose on its Supplement Facts panel.
The rung is decided by what a buyer can look up, not by what the label says. Rung 1 means the exact product appears in a certifier’s public registry; the listing text is quoted so you can find it. Rung 2 means the brand publishes a certificate of analysis for a specific lot. Rung 3 is a lab report with no lot to match. Rung 4 is a claim, silence, or a brand site that blocked our check. Within a rung, products are ordered by cost per 4 g serving.
| Product | Rung | Certification registry | Published lab report | Label says | Cost per 4 g | Buy |
|---|---|---|---|---|---|---|
| Wholesome Story Myo-Inositol & D-Chiro Inositol 40:1 | 1 · Certified | NSF/ANSI 173 "Myo & D-Chiro Inositol" · registry | claim, no document found | nothing stated | $1.53 | Check price |
| Ovasitol by Theralogix 90-day supply | 1 · Certified | NSF/ANSI 173 "Ovasitol® Inositol Supplement" · registry | claim, no document found | NSF Certified | $1.88 | Check price |
| Micro Ingredients Myo & D-Chiro Inositol Powder 40:1 | 4 · Unverified | not found in NSF, USP or Informed Sport listings | claim, no document found | nothing stated | $0.28 | Check price |
Registry listings are from our snapshot of each registry on the date shown; a listing can be added or withdrawn after that date, so confirm the lot on your bottle against the live registry before relying on it. Prices are the current Amazon price divided by servings.
What each mark actually checks
NSF/ANSI 173 (the “NSF Contents Certified” mark, listed at info.nsf.org) verifies that the label is accurate, that contaminants such as heavy metals and microbes are within limits, and audits the manufacturing facility. NSF Certified for Sport is the same program plus a screen of every lot for more than 280 substances banned by major athletic organizations; it is the mark most professional leagues and anti-doping bodies name. USP Verified checks identity, potency and contaminants, that a tablet or capsule dissolves, and audits manufacturing to USP’s standard; its list is short (159 products in our snapshot) and dominated by a few large brands. Informed Sport tests every batch for banned substances at an ISO 17025 laboratory and publishes the batch; Informed Choice tests retail samples on a schedule instead of every batch. None of these programs measures whether myo-inositol works; they measure whether the container holds what the label says.
Inositol is bought mostly by women managing PCOS, often for months and often while trying to conceive, which is exactly when a buyer wants to know the powder is what it says. It is also a category where two of the three products we track are in NSF's finished-product listing, under two different NSF programs: Ovasitol carries NSF Contents Certified, and Wholesome Story's 40:1 blend is listed as well. The third states third-party testing with no document we could load.
The dose the trials used is the reason the powder has to be right. A meta-analysis of randomized trials in women with PCOS found myo-inositol lowered fasting insulin and the HOMA insulin-resistance index, with a trend toward lower testosterone and higher SHBG after 24 weeks (Unfer 2017, PMID 29042448), typically at 2 g twice a day; a scoop that under-delivers under-doses a months-long protocol. The general case for certified products over claims is made in the contamination literature (Mathews 2018, PMID 28850291).
Which myo-inositol to buy
Product links go to Amazon and we may earn a commission if you buy. It never changes which product we pick or what we say about it. How we choose.
How to check your own tub
- Find the lot number, usually stamped on the bottom or near the seal.
- NSF: search the product at info.nsf.org (NSF/ANSI 173) or nsfsport.com (Certified for Sport). The listing names the exact product and form.
- Informed Sport / Informed Choice: search the brand at sport.wetestyoutrust.com; each product page lists tested batches.
- USP Verified: the list is at quality-supplements.org.
- Brand COAs: the “view” links in the table go to the report pages we found; match your lot number. A report without a lot number is rung 3, not rung 2.
Frequently asked questions
Which myo-inositol supplements are third-party tested?
Of the 3 myo-inositol products we track, 2 are listed in an independent certification registry as of 2026-08-25: Wholesome Story Myo-Inositol & D-Chiro Inositol 40:1 (NSF/ANSI 173); Ovasitol by Theralogix 90-day supply (NSF/ANSI 173). Micro Ingredients Myo & D-Chiro Inositol Powder 40:1 says "tested" on the label with no registry listing and no document we could find.
What is the cheapest certified myo-inositol?
Wholesome Story Myo-Inositol & D-Chiro Inositol 40:1 at $1.53 per 4 g at current Amazon prices, listed as "Myo & D-Chiro Inositol" in the NSF/ANSI 173 registry. The cheapest myo-inositol of any kind we track, Micro Ingredients Myo & D-Chiro Inositol Powder 40:1, is $0.28 per serving on rung 4.
What is the difference between NSF Certified for Sport, NSF/ANSI 173, USP Verified and Informed Sport?
All four are independent programs that test finished products and audit the factory; the difference is what they test for. NSF/ANSI 173 checks that the label is accurate and contaminants are within limits. NSF Certified for Sport adds a screen of every lot for more than 280 substances banned by major athletic organizations. USP Verified checks identity, potency, contaminants and that the pill dissolves, and audits manufacturing. Informed Sport tests every batch for banned substances at an ISO 17025 laboratory; Informed Choice tests retail samples of the product on a schedule rather than every batch. A product in any of these registries is on rung 1 of our ladder; the registry, not the logo on the container, is the evidence.
Does "third-party tested" on a label mean anything?
On its own, no. The phrase has no legal definition, and a brand can print it after sending one sample to a lab once. The question to ask is whether you can check: is the product in a certifier's registry, or does the brand publish a certificate of analysis with a lot number you can match to your bottle? In the botanical sports-supplement aisle a 2023 analysis found 89% of products mislabelled and 12% containing FDA-prohibited ingredients (Cohen 2023); the rule is the same everywhere: evidence you can look up beats a claim.
What is the difference between NSF Contents Certified and NSF Certified for Sport?
Both are NSF programs and both appear in the NSF/ANSI 173 listing. Contents Certified verifies that the label is accurate, that contaminants are within limits and that the facility passes audit. Certified for Sport adds a screen of every lot for more than 280 banned substances. For inositol, which no athlete is tested for, Contents Certified is the relevant mark; Ovasitol carries it.
Is Wholesome Story inositol NSF certified?
It is in NSF's finished-product listing as "Myo & D-Chiro Inositol" (Wholesome Story), which places it on rung 1. The brand's own page shows a Clean Label Project badge without a linked report; the NSF listing is the checkable evidence.
How do I check my own tub?
Look for the lot number on the container. For NSF, search the product at info.nsf.org or nsfsport.com; for Informed Sport, search the brand at sport.wetestyoutrust.com and the lot on the product's page; for USP, check quality-supplements.org. For a brand that publishes certificates of analysis, find the COA page on its site and match the lot number. If none of those works, you are trusting the label.
Related guides
- Best inositol, ranked
- Inositol for PCOS
- Theralogix vs Micro Ingredients
- Inositol dosage guide
- How few supplements are certified at all: the registry audit
Sources
- NSF. NSF/ANSI 173 Dietary Supplements, certified finished products listing. info.nsf.org (snapshot 2026-08-25, 3053 listings) and NSF Certified for Sport program. nsfsport.com
- USP. USP Verified Dietary Supplements, verified products list. quality-supplements.org (159 products)
- LGC. Informed Sport and Informed Choice certified product search. sport.wetestyoutrust.com (2105 products)
- Brand certificate-of-analysis and quality pages linked in the table, each checked 2026-09-19.
- Unfer V, et al. “Myo-inositol effects in women with PCOS: a meta-analysis of randomized controlled trials.” Endocr Connect. 2017. PMID: 29042448
- Mathews NM. “Prohibited Contaminants in Dietary Supplements.” Sports Health. 2018. PMID: 28850291
- Cohen PA, et al. “Presence and Quantity of Botanical Ingredients With Purported Performance-Enhancing Properties in Sports Supplements.” JAMA Netw Open. 2023. PMID: 37459101