Vitamin C Dosage Calculator
Calculate your personalised vitamin c dose based on Australian guidelines. NHMRC RDI: 45 mg/day (male) / 45 mg/day (female).
Calculate Your Dose
Important Warnings
- Doses above 2,000 mg/day increase kidney stone risk (especially in men).
- Absorption drops significantly above 200 mg per dose — split doses.
- Megadoses (5+ g) can cause diarrhea and stomach cramps.
- Stop high-dose vitamin C 2 weeks before surgery (may affect blood clotting tests).
Tips for Better Absorption
- You probably get enough from diet if you eat fruit and vegetables daily.
- Split doses are more effective than a single large dose.
- Take with iron to boost iron absorption by 67%.
- Cooking destroys vitamin C — eat fruits and vegetables raw when possible.
Frequently Asked Questions
Does vitamin C prevent colds?
No — regular vitamin C supplementation does NOT prevent colds in the general population. However, it reduces cold duration by about 8% in adults and 14% in children when taken daily before getting sick. Starting after symptoms appear has minimal effect.
Is 1,000 mg of vitamin C too much?
Not necessarily, but your body can only absorb about 200 mg at a time. Above that, absorption drops and excess is excreted in urine. Split doses (e.g., 500 mg twice daily) are more effective than a single 1,000 mg dose.
Should smokers take more vitamin C?
Yes. Smokers have lower vitamin C levels and should take an additional 35 mg/day above the standard RDI. Smoking increases oxidative stress, which depletes vitamin C faster.
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This calculator provides general guidance based on Australian NHMRC guidelines and published clinical research. It is not medical advice. Individual needs vary. Always consult a healthcare professional before starting any supplement, especially if you are pregnant, breastfeeding, taking medications, or have a medical condition.