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Vitamin C

Vitamin C supports immune function, collagen synthesis, and antioxidant defense.

Our vetting standard

Every vitamin c formula here clears the same bar.

  • Clinically studied, effective doses
  • Bioavailable, well-absorbed forms
  • Practitioner-grade, trusted brands
  • Third-party tested for identity and potency

See if it's actually working

Plasma vitamin C saturates quickly, so once the level is in range a higher dose buys nothing but more excreted vitamin C.

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Vitamin C FAQs

How much vitamin C should I take?

RDA is 75–90 mg/day, but most supplements provide 500–1,000 mg. Higher doses (1–2 g/day) saturate plasma. Liposomal vitamin C reaches higher blood levels with less GI upset. Acute illness doses go up to 3–4 g/day in divided doses.

Will vitamin C prevent colds?

It doesn't prevent colds in the general population, but daily supplementation reduces cold duration by about 8% in adults and 14% in children. Higher acute doses at the first sign of symptoms may also shorten illness.

What form of vitamin C is best?

Ascorbic acid is fine for most people. Buffered forms (calcium ascorbate, magnesium ascorbate) are gentler on the stomach. Liposomal vitamin C reaches the highest blood levels. Avoid mega-dosing without need — excess is excreted.

Vitamin C from food vs. supplements?

Food sources (citrus, bell peppers, kiwi, strawberries, broccoli, cantaloupe) come with bioflavonoids and other nutrients that enhance absorption. For RDA-level needs, food is plenty. For higher therapeutic doses (1,000+ mg), supplements are practical.

Should I take vitamin C with iron?

Yes, if you're iron-deficient — vitamin C significantly boosts non-heme iron absorption (especially from plant sources). Take 200–500 mg vitamin C with iron supplements or iron-rich plant foods. People with iron overload conditions should avoid this combination.

Can vitamin C cause kidney stones?

In susceptible people (especially men with a history of calcium oxalate stones), high-dose vitamin C (above 1,000 mg/day) may slightly increase stone risk because it converts to oxalate. Stay below 500–1,000 mg if you have a stone history.

Liposomal vs. regular vitamin C?

Liposomal vitamin C is encapsulated in phospholipids, which protects it during digestion and improves absorption. It reaches higher blood levels with smaller doses and less GI upset. It's pricier — worth it for therapeutic doses, less necessary for daily maintenance.

Is high-dose vitamin C safe?

Up to 2,000 mg/day is the upper limit. Doses above this can cause GI upset, diarrhea, and theoretically kidney stones in susceptible people. IV vitamin C bypasses these limits but should only be done in clinical settings.

When should I take vitamin C?

Anytime, but with food if it causes stomach upset. Vitamin C has a 30-minute absorption window, so divided doses (250–500 mg twice daily) are better than one large dose. Take separately from copper or vitamin B12 absorption isn't significantly affected.