Most vitamin C marketing sells you a bigger number. Thorne quietly does the opposite — a 500 mg capsule that, taken twice a day, keeps you near the absorption window instead of flushing a gram at once. Pair that with the most respected independent-testing program in the aisle, and you have the one bottle we'd hand someone who just wants to get vitamin C right without thinking about it.
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Read the complete Vitamin C guide →Standard ascorbic acid with 75 mg citrus bioflavonoids — no absorption-enhancing chemistry, so uptake follows the same saturable curve as any oral C. It earns its points on the 500 mg unit size, which lets you dose near the ~200 mg absorption window rather than overshoot it.
Thorne runs one of the deepest brand-wide third-party testing programs in the supplement industry and is a default among clinicians. It's not a per-lot USP seal, but the verification story is the strongest in this group.
500 mg per capsule is the smartest dose here. Split morning and evening and you stay near plasma saturation without the steep diminishing returns of a 1,000 mg single dose.
Unbuffered ascorbic acid, so not the gentlest option — but the lower 500 mg unit is inherently easier on the stomach than the gram tablets, and the corn-free, gluten-free formula suits sensitive users.
About $0.14 per 500 mg capsule works out to roughly $0.28 per gram — mid-pack. You're paying for testing rigor, not a low ingredient cost.
“A 500 mg split-dose schedule improves fractional absorption versus a single 1,000 mg dose.”
Levine 1996 (PNAS) and Padayatty 2004 (Ann Intern Med) show oral vitamin C absorption is saturable and fractional bioavailability falls at gram doses, so two 500 mg doses stay nearer the absorption window than one 1,000 mg bolus.
“Brand-wide third-party tested.”
Thorne operates one of the most extensive independent testing programs in the industry and is widely corroborated as clinician-trusted; verification is not limited to a single flagship lot.
“The 75 mg citrus bioflavonoids meaningfully boost vitamin C absorption.”
Human evidence that bioflavonoids raise vitamin C bioavailability at these doses is weak and inconsistent; treat the flavonoids as a minor cofactor, not an absorption lever.
“Clean formula: no corn-derived vitamin C and gluten-free.”
Consistent with the product label and Thorne's published sourcing standards.
Oral vitamin C saturates: Levine's pharmacokinetic data put near-complete plasma saturation around 200-400 mg/day. A 500 mg unit taken twice daily tracks that curve far better than a single 1,000 mg tablet, most of which is excreted.
Across this category, independent verification is what separates a trustworthy bottle from a leap of faith. Thorne's brand-wide program is the strongest here, which is why it outranks cheaper picks.
The 75 mg citrus bioflavonoid content is fine to have, but don't pay a premium for it — the human absorption-boost data are thin. Judge this bottle on dose design and testing.
To reach a full gram you take two capsules, roughly doubling cost per gram to ~$0.28. If you only ever want 500 mg/day that's irrelevant; if you want 1,000 mg cheaply, look at Nature Made.
This wins on the two things that actually move the needle — independent testing and a dose you can use intelligently — rather than on a marketing form. The 500 mg cap lets you dose near the saturation point instead of flushing a megadose. If you want one bottle you can trust and use correctly, start here.
Check Thorne on AmazonPlasma vitamin C follows sigmoid kinetics with near-complete saturation around 200-400 mg/day and no added plasma benefit above ~400 mg/day, supporting split, moderate dosing.
Oral vitamin C is tightly regulated by intestinal absorption and renal excretion, so oral megadoses cannot push plasma meaningfully beyond the saturation set point.
