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Water-Soluble Vitamin (Vitamin C)

Ascorbic Acid (Vitamin C)

Brand names: Redoxon, generic

Adult dose

Dose: Scurvy prevention/treatment: 25–75 mg daily (prevention); 250 mg–1 g daily in divided doses (treatment). Iron absorption enhancement: 200 mg with each iron dose. Urinary acidification: 4–12 g daily
Route: Oral (also IV/IM available for severe deficiency or specific indications)
Frequency: Once to 4 times daily depending on indication

Clinical pearls

  • Deficiency causes scurvy: perifollicular haemorrhages, gum disease, impaired wound healing, corkscrew hairs
  • UK dietary reference value: 40 mg/day (adult); pregnancy: 50 mg/day; breastfeeding: 70 mg/day
  • High-risk groups: smokers, elderly, those with poor diet, alcohol misuse, malabsorption
  • Urinary acidification with high-dose ascorbic acid reduces UTI and catheter encrustation in some patients
  • No good evidence that megadose supplementation prevents colds, cancer, or CVD in well-nourished adults
  • IV high-dose ascorbic acid used experimentally in sepsis/critical care (not standard of care)

Contraindications

  • Hyperoxaluria (risk of renal stones — high doses promote oxalate formation)
  • Haemochromatosis or other iron overload states (vitamin C increases iron absorption)
  • G6PD deficiency (very high IV doses may cause haemolysis)

Side effects

  • GI disturbance (nausea, diarrhoea) with high doses
  • Renal oxalate stones with chronic high doses (>1 g/day)
  • Prooxidant effects in iron-overload states
  • Haemolysis in G6PD deficiency (high IV doses)

Interactions

  • Iron supplements — vitamin C enhances non-haem iron absorption (clinical benefit for iron-deficiency anaemia)
  • Deferoxamine — ascorbic acid mobilises iron; use with caution in cardiac failure patients
  • Warfarin — high-dose vitamin C may reduce INR in some patients; monitor
  • Bortezomib — ascorbic acid may reduce bortezomib efficacy; avoid concurrent high-dose supplementation during treatment

Monitoring

  • Serum ascorbic acid levels if deficiency suspected (normal >23 µmol/L; scurvy <11 µmol/L)
  • Renal function and urinary oxalate if chronic high-dose use
  • Response of scurvy symptoms within days to weeks

Reference: BNF; NHS Vitamins and minerals guidance; NICE CKS Vitamin deficiency; Scientific Advisory Committee on Nutrition (SACN) UK dietary reference values; https://bnf.nice.org.uk/drugs/ascorbic-acid/. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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