Thorne Riboflavin 5'-Phosphate

Riboflavin's richest food sources are dairy, eggs, and meat, so athletes eating a mostly plant-based diet often take in less of it to begin with, while training volume burns through it faster than a sedentary person would. Hard training adds a second problem on top of that gap. It stresses the digestive system in ways that can make converting standard riboflavin into its usable form less reliable, right when your body needs that energy metabolism pathway working normally.

Thorne's Riboflavin 5'-Phosphate solves both problems by skipping the conversion step entirely. It delivers 36.5mg of the already-active form directly, so there's nothing left for your gut to convert and nothing lost if that conversion process isn't working at full capacity.

Already in active form – This is riboflavin 5'-phosphate (also called FMN), the coenzyme form your cells actually use, not the raw riboflavin that still needs converting.

Dosed on its own, not buried in a blend – General B-complex and electrolyte formulas typically include a small amount of B2 alongside several other nutrients. This is isolated, so you can dose it independently when that's what you actually need.

A cofactor for other B vitamins – Riboflavin is required to activate vitamin B6 and to convert tryptophan into niacin and folate into its active forms, so a shortfall here can bottleneck other B vitamins too.

Riboflavin functions as a coenzyme in two forms, FMN and FAD, both involved in the redox reactions that generate cellular energy from carbohydrates, fats, and protein. It also plays a role in red blood cell synthesis, methylation, and glutathione recycling, the pathway your cells use to regenerate one of their main antioxidants. One harmless side note worth knowing ahead of time: high-potency B2 can turn your urine bright yellow. That's just riboflavin being excreted and isn't a sign anything's wrong.

How to Use Thorne Riboflavin 5'-Phosphate

Dose: Take one capsule one to three times daily, with food if you prefer.

If you're already taking a B-complex or electrolyte formula: Check how much riboflavin you're already getting before adding this on top, since it delivers a concentrated single dose rather than a balanced complex.

This product is contraindicated for anyone with a history of hypersensitivity to its ingredients. Consult your healthcare provider before use if pregnant.