About Thorne
Thorne was founded in 1984 by Al Czap, starting as a small manufacturer in Seattle before relocating production to Sandpoint, Idaho, in 1990. The company now manufactures its supplements at an NSF-certified facility in Summerville, South Carolina, independently certified both for general Good Manufacturing Practices and for the additional standard required to produce NSF Certified for Sport products. Thorne sold primarily through physicians and other healthcare practitioners for most of its history, launching direct-to-consumer sales in 2018. In 2021 it merged with health-data company Onegevity to form Thorne HealthTech, which traded on Nasdaq under the ticker THRN until consumer-focused private equity firm L Catterton acquired the company in a deal reported at $680 million, completed in October 2023.
Thorne holds one of the largest lines of NSF Certified for Sport products of any supplement brand and describes itself as the exclusive nutritional supplement partner of U.S. National Teams, used by more than 100 professional sports teams. It is also the only supplement manufacturer publicly collaborating directly with Mayo Clinic on published research, including a randomized, placebo-controlled trial with Mayo Clinic and HealthTech Connex on dietary supplementation and brain function and structure in junior ice hockey players. That research and certification focus shows up in the specific ingredient forms across its catalog: methylcobalamin instead of cyanocobalamin for B12, iron bisglycinate instead of ferrous sulfate, and zinc picolinate instead of zinc gluconate, the more bioavailable and typically gentler form in each case.
Brand website: thorne.com
What Thorne makes
Thorne's range runs wider than the products we review. The lines we know best from our own testing are marked with a star:
Vitamin B12 (Methylcobalamin)
NSF Certified for Sport and TGA-certified capsule using the bioactive coenzyme form of B12 — featured on BestRatedDocs
Chelated Minerals: Iron Bisglycinate & Zinc Picolinate
gentler, more bioavailable chelated forms than the ferrous sulfate and zinc gluconate found in mass-market brands — featured on BestRatedDocs
Vitamin K Complex (K1 + MK-4 + MK-7)
all three clinically relevant vitamin K forms combined in one third-party tested capsule — featured on BestRatedDocs
Basic Prenatal
high-potency methylfolate and Ferrochel iron bisglycinate formula aimed at practitioner-directed pregnancy care — featured on BestRatedDocs
FiberMend Prebiotic Fiber
low-FODMAP Sunfiber-based powder with a larch arabinogalactan and apple pectin prebiotic blend — featured on BestRatedDocs
Recovery & Sleep Support: NAC, Theanine, Melaton-3
NSF Certified for Sport NAC and melatonin, plus an NSF Contents Certified L-theanine capsule — featured on BestRatedDocs
CoQ10 & Heart Health
cellular-energy and cardiovascular support line outside our reviewed categories
Why we recognized Thorne
The BestRatedDocs Top Brand recognition isn't paid for and can't be applied for. We award it to the brands whose products consistently stand out in our category reviews. Thorne earned it on the strength of the products below, evaluated the same way every product on this site is: assessed against clinical criteria, verified specifications, and real-world user outcomes, and judged on merit.
Thorne products we rated highly
Thorne Vitamin B12 as Methylcobalamin, 60 Capsules
NSF Certified for Sport and TGA-certified methylcobalamin, the bioactive coenzyme form of B12 that skips the hepatic conversion cyanocobalamin requires. Flexible one-to-three-capsule dosing supports both maintenance and deficiency correction, and it carries a 4.8-star rating across more than 3,300 reviews.
Read the 7 Best B12 Supplements of 2026 guide →
Thorne FiberMend Prebiotic Fiber Powder
Built on Sunfiber, a clinically studied, low-FODMAP partially hydrolyzed guar gum that reviewers say produces none of the bloating or gas common with psyllium. It dissolves completely and adds a prebiotic blend of larch arabinogalactan and apple pectin for gut-flora support beyond basic fiber bulking.
Read the 7 Best Fiber Supplements of 2026 guide →
Thorne Iron Bisglycinate 25 mg, 60 Capsules
Iron bisglycinate chelate that is significantly less likely to cause constipation or stomach upset than ferrous sulfate, backed by NSF Certified for Sport testing for purity and freedom from banned substances. The 25 mg dose is sized for maintenance supplementation and for patients who do not tolerate higher-dose iron.
Read the 7 Best Iron Supplements of 2026 guide →
THORNE Theanine, 200mg L-Theanine Supplement, 90 Capsules
The only L-theanine in our review carrying a genuine product-level third-party certification, NSF Contents Certified, which verifies what is actually in the capsule rather than only where it was manufactured. It delivers the standard 200 mg clinical dose with a clean excipient list.
Read the 10 Best L-Theanine Supplements of 2026 guide →
Thorne Melaton-3 Capsules, 60 Count
NSF Certified for Sport melatonin independently tested for over 300 banned substances, in a clean 3 mg capsule free of fillers, flavors, sweeteners, and major allergens. Our research found Thorne to be among the supplement brands most frequently recommended by U.S. healthcare practitioners.
Read the 8 Best Melatonin Supplements of 2026 guide →
THORNE NAC, 500 mg N-Acetylcysteine, Amino Acid Supplement, 90 Capsules
The only NSF Certified for Sport NAC we found on Amazon, formulated specifically for respiratory support with a focus on mucus clearance and lung antioxidant activity. Reviewers report measurable liver-panel improvements at the 500 mg dose.
Read the 13 Best NAC Supplements of 2026 guide →
Thorne Basic Prenatal (90 Capsules)
Carries the highest-potency methylated folate (1 mg 5-MTHF) and the highest, gentlest chelated iron dose (45 mg Ferrochel bisglycinate) in our prenatal lineup, plus methylated B12 for full methylation-pathway support, formulated for practitioner-directed pregnancy care.
Read the 7 Best Prenatal Vitamins of 2026 guide →
Thorne Vitamin K (K1 + MK-4 + MK-7), 60 Capsules
Combines all three clinically relevant vitamin K forms, K1, MK-4, and MK-7, in a single capsule that is third-party tested and free of gluten, dairy, and soy. It ties for the highest rating in our vitamin K2 review at 4.8 stars.
Read the 10 Best Vitamin K2 Supplements of 2026 guide →
Thorne Zinc Picolinate 30 mg (180 Capsules)
NSF Certified for Sport zinc picolinate, the most bioavailable zinc form in our review, dosed at a clinically appropriate 30 mg and manufactured in Thorne's own facility with pharmaceutical-grade raw-material verification. It holds a 4.8-star rating across more than 11,000 reviews.
Read the 7 Best Zinc Supplements of 2026 guide →What earned Thorne the recognition
- Thorne products earned a place as a top pick in nine separate BestRatedDocs supplement reviews, spanning B12, iron, zinc, vitamin K2, fiber, NAC, L-theanine, melatonin, and prenatal vitamins, a breadth of categories that reflects consistent formulation quality rather than strength in a single niche.
- NSF Certified for Sport is Thorne's most distinguishing credential: the brand describes itself as the exclusive nutritional supplement partner of U.S. National Teams and used by more than 100 professional sports teams, a level of banned-substance testing our reviews rarely find matched.
- Thorne is the only supplement manufacturer we found publicly collaborating directly with Mayo Clinic on published research, including a randomized, placebo-controlled clinical trial on dietary supplementation and brain health.
- Manufacturing is concentrated in Thorne's own South Carolina facility, independently certified both for general Good Manufacturing Practices and for the additional standard required to produce NSF Certified for Sport products.
- Across the products we reviewed, Thorne consistently chose the more bioavailable, better-studied ingredient form: methylcobalamin over cyanocobalamin, iron bisglycinate over ferrous sulfate, and zinc picolinate over zinc gluconate.