Thorne Iron vs. Gut Bug-Free: Tested, NSF-Certified Supplement Engagement We’ve tested many iron supplements, but Thorne’s Iron Bisglycinate impresses with its gentle, NSF-certified formula. Our bodies absorb 25 mg of iron efficiently without gut distress, a rare win in the world of iron supplements. The capsule size is easy to swallow, and the gluten-free design caters to our dietary needs—perfect for athletes and sensitive individuals. NSF certification for sport ensures our product is third-party verified, reducing concerns about purity and safety. While results take time, our experience so far is promising. We appreciate Thorne’s focus on bioavailability and tolerability. For those struggling with iron deficiency without the usual side effects, this supplement is a standout choice. The 60-capsule bottle offers convenient, long-term use with balanced daily dosing. If you value absorption and GI comfort, this is worth trying.