The 5 Best Inositol Supplements of 2026, Ranked on Their Labels

Four capsules give 2,000 mg of myo-inositol and 50 mg of D-chiro-inositol, listed separately. At $14.95 for 120 capsules it costs $0.50 per 2,000 mg day, and the 2-pack at $26.90 brings that to $0.45. If you want the 40:1 label in a capsule for the least money, this is it, and we say so plainly. The other ingredients line lists a hypromellose capsule, rice flour, magnesium stearate and silica.

The label says 3rd-party tested by independent, ISO-accredited laboratories and made in an NSF certified facility. That is a lab claim and a facility certificate, not a product-level mark like Ovasitol's. Neither the Amazon listing nor the brand page we read states a money-back guarantee. It has 4.6 stars from 1,056 ratings and the lowest 1-star share here, 2%. Amazon's own review summary says: “While some customers report improved cramps, others experience bloating, and there are mixed experiences with cycle compatibility.” One reviewer on the brand's own site wrote that bottles often hold 119 capsules rather than 120, so the last dose comes up short.

This is the #1 seller in Amazon's inositol category, with 36,290 ratings. A 4-capsule serving is 2,000 mg of myo-inositol and 50 mg of D-chiro-inositol, listed separately. It carries the Clean Label Project Purity Award for the sixth year and NSF Contents Certified and NSF Gluten-Free marks, the best paperwork here with Ovasitol. At $27.95 for 120 capsules it costs $0.93 per 2,000 mg day, the highest in the set. The 360-count bottle at $63.99 brings that down to $0.71, level with Dosera. No money-back guarantee is stated on the listing or the brand page we read.

Two label problems. The Amazon listing says use 1 to 2 servings, 4 to 8 capsules, as needed, so a bottle lasts 30 days or 15. And the Amazon panel names a methylcellulose capsule while the brand site says hypromellose. Its rating is 4.4, the lowest of the four, with 5% at 1 star, which is 1,829 one-star ratings. Amazon's own review summary says: “the side effects and value for money receive mixed feedback - while some say it doesn't upset their stomach and consider it worth the purchase, others report nausea and find it not worth the money.” A Walmart reviewer wrote that the only downside would be the 4 pill dosage. A Straight.com roundup called it a bit pricey compared to other myo-inositol supplements.

One scoop is 2,000 mg of myo-inositol and 50 mg of D-chiro-inositol, listed separately. The ingredients line reads myo-inositol and D-chiro-inositol and nothing else. It is NSF certified for contents, and it wins the testing bar on this page outright. The canister holds 180 scoops for $86.68, which is $0.48 per 2,000 mg day, cheaper than any 40:1 capsule here, Dosera included.

Three things count against it on our criteria. The first canister is $86.68, the most expensive way to find out if inositol suits you. It is a powder you measure and mix, and taste is the third most tagged topic in its Amazon reviews; a Walmart review summary notes that some users detect sweetness or a funky taste. And neither the Amazon listing nor the brand page we read states a money-back guarantee. The label dose is two scoops a day, 4,000 mg, so following the label costs $28.89 a month. Amazon's own review summary says: “While some customers feel better overall and consider it worth the price, others experience stomach/GI upset and find it not worth the cost.” One Reddit owner, quoted through an aggregator, called it a little pricey but said it worked the best. Its 1-star share is 5%.

The label is one line: inositol powder, 730 mg per quarter teaspoon, other ingredients none. A pound is 454 g for $29.99, which is $0.13 per 2,000 mg day. Nothing else on this page comes close on cost per mg, and we say so plainly. If your doctor told you to take myo-inositol alone, this is the cheapest way to do it.

It is last here because the page ranks 40:1 bottles against the combined studies, and this has no D-chiro-inositol at all [6]. The label dose is 730 mg once a day, about a third of the 2,000 mg the studies used [1, 4]. To reach 2,000 mg you measure almost three quarter-teaspoon servings of loose powder, and the listing mentions no scoop. The testing line is NOW's own in-house labs and an A-rated GMP facility, not a product certificate, and no money-back guarantee is stated. Amazon's own review summary says customers “appreciate its mild sweet taste” and that “while many report no serious side effects, some experience nausea and diarrhea.” One reviewer on a mirror site noted that many people underdose. Its 1-star share is 4%.