Ascorbic acid (vitamin C) supplementation in adults

See Clinical aspects of key water-soluble vitamins for the physiological function of ascorbic acid (vitamin C), and the effects of and risk factors for ascorbic acid deficiency.

To treat ascorbic acid deficiency in adults, use:

Testing after supplementation is rarely needed and should be individualised—it may be required in patients using parenteral nutrition. Vitamin C testing is complex and can result in inaccurate concentrations if not processed correctly—consider retesting the patient’s vitamin C blood concentration if the result is incongruent to the patient presentation. Long-term supplementation is not required if dietary intake improves.

Vitamin C blood concentration may be decreased in acute or chronic inflammatory conditions, or infections—consider if inflammation or infection are present before supplementationMcMillan, 2019.

Ascorbic acid doses higher than 2 g daily can cause adverse effects, including kidney stones, stomach cramps and diarrhoea.