Are there reasons to stop taking vitamin C (ascorbic acid)?

Reasons to Stop Vitamin C Supplementation

Vitamin C supplementation should be stopped in patients with hemochromatosis or iron overload conditions, as it can accelerate iron deposition and potentially cause cardiac deterioration. 1

Absolute Contraindications Requiring Discontinuation

Stop vitamin C supplementation immediately if the patient has:

• Hemochromatosis (especially during iron overload or induction phase of treatment) - Vitamin C enhances non-heme iron absorption and can mobilize iron from reticuloendothelial stores, leading to increased iron availability and free radical generation. Case reports have documented high-dose vitamin C accelerating iron deposition and cardiac deterioration in severe hemochromatosis. 1

• Thalassemia major with iron overload - Oral vitamin C supplementation has been associated with acute deterioration of cardiac function in these patients due to iron mobilization and increased free radical generation. 1

• G6PD deficiency - High-dose vitamin C poses hemolytic risk in these patients. 2

• Active oxalate kidney stones or history of recurrent oxalate stones - Vitamin C is metabolized to oxalate, increasing stone formation risk. 2, 3

• Renal insufficiency or chronic hemodialysis - These patients cannot adequately clear vitamin C metabolites, leading to potential oxalate accumulation. 3

Relative Contraindications Requiring Dose Reduction or Cessation

Consider stopping or reducing vitamin C if:

• Renal dysfunction is present - Monitor closely as high doses increase oxalate excretion. 4, 3

• Gastrointestinal side effects develop - Doses exceeding 2 grams can cause diarrhea and abdominal discomfort. 4, 5

• The patient is taking it for unproven indications - For general health in healthy individuals, there is insufficient evidence that doses above the RDA (75-90 mg/day) provide benefit for preventing cancer or cardiovascular disease. 1

Clinical Context: When Continuation May Be Harmful

In patients with iron overload conditions:

• Vitamin C acts as a pro-oxidant rather than antioxidant when iron is present in excess. 1
• The EASL guidelines specifically recommend avoiding supplemental vitamin C in hemochromatosis patients, especially before iron depletion is achieved. 1
• If supplementation is absolutely necessary after iron depletion, limit dosage to maximum 500 mg daily and only after physician discussion. 1

In sepsis treatment:

• The Surviving Sepsis Campaign recommends against routine vitamin C use in pediatric septic shock (weak recommendation). 2
• High-dose vitamin C (6 g/day) showed no significant benefit in reducing organ dysfunction scores in the C-EASIE 2025 trial. 2
• Do not delay standard sepsis care to administer vitamin C. 2

Important Caveats

• Vitamin C from dietary sources (fruits, vegetables) does not pose the same risks as supplementation - There is no evidence that dietary vitamin C from foods is harmful even in smokers or patients with iron overload. 1

• Doses greatly exceeding the RDA should be avoided without clear indication - Some vitamins like A and D are harmful in high doses; while vitamin C is generally safer, the tolerable upper limit is 2 grams based on gastrointestinal effects. 1, 6

• Beta-carotene (not vitamin C) has the strongest evidence of harm - In smokers, beta-carotene supplementation increased lung cancer incidence and all-cause mortality. 1