Water-Soluble Vitamin (Vitamin C) Pregnancy: No clinical data on exposed pregnancies available; animal studies do not indicate direct or harmful effects. Pregnant women should exercise caution. Ascorbic acid is excreted in breast milk — caution advised, though no evidence that this is hazardous to the infant.

Ascorbic Acid (Vitamin C)

Brand names: Redoxon, generic

Ascorbic acid (vitamin C) is a water-soluble vitamin used to prevent and treat vitamin C deficiency, including scurvy, and is sometimes used to acidify the urine.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Not less than 250 mg daily, in divided doses

Route: Oral

Frequency: Daily, in divided doses

Max: Adults and children over 12 years: 1000 mg daily. Children 4–11 years: 500 mg daily.

SPC posology is stated for "Adults and children over 4 years" as a treatment dose of not less than 250 mg daily in divided doses. The elderly: as for adults — as dietary intake of vitamin C may be less in the elderly, they are at greater risk of being deficient in this vitamin. Source SPC is Ascorbic Acid 100 mg Tablets; no dose is stated for children under 4 years and no mg/kg dosing is given. Patients known to be at risk of hyperoxaluria should not ingest ascorbic acid in doses exceeding 1 gram daily. Ascorbic acid may interfere with tests/assays for urinary glucose, uric acid, creatinine and faecal occult blood.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to ascorbic acid or to any of the excipients
Hyperoxaluria — ascorbic acid should not be given to these patients

Side effects

Diarrhoea with large doses
Increased urinary oxalate excretion in patients at risk of hyperoxaluria (doses above 1 g daily)
Haemolytic anaemia in individuals with glucose-6-phosphate dehydrogenase deficiency
Rebound deficiency if prolonged high intake is reduced or withdrawn rapidly (increased renal clearance)
Diuretic effect at doses of more than 600 mg

Interactions

Amphetamines — ascorbic acid may reduce their absorption
Iron — ascorbic acid may increase oral iron absorption
Desferrioxamine — enhanced urinary iron excretion and increased risk of cardiovascular adverse effects; use with caution and monitor cardiac function
Aspirin — concomitant administration may interfere with absorption of ascorbic acid
Aluminium-containing antacids — may increase urinary aluminium elimination; concurrent use not recommended, especially in renal insufficiency
Amygdalin (complementary medicine) — co-administration can cause cyanide toxicity

Clinical monograph

How it works

It is an essential cofactor for collagen synthesis and several enzymatic hydroxylation reactions and acts as a water-soluble antioxidant.

Prescribing in practice

Prolonged high-dose use can predispose to oxalate renal stones and may be hazardous in patients with renal impairment or a history of oxalate calculi.
Reserve treatment for genuine deficiency, which is uncommon other than with poor diet, malabsorption or increased requirements.
Vitamin C can interfere with some laboratory and point-of-care tests, including blood glucose and urinalysis results.

Monitoring

Monitoring is usually clinical, based on resolution of deficiency features; specific laboratory monitoring is not routinely required.

Counselling the patient

A balanced diet usually provides enough vitamin C.
Avoid taking very high doses long term without advice.
Tell your clinician if you have had kidney stones.

Evidence & guidelines

Vitamin C is established treatment for scurvy and deficiency, while evidence does not support routine high-dose use to prevent or treat common colds.

Reference: NHS Vitamins and minerals guidance; NICE CKS Vitamin deficiency; Scientific Advisory Committee on Nutrition (SACN) UK dietary reference values; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways