(More information) There is no scientific evidence that large amounts of vitamin C (up to 10 grams [g]/day in adults) exert any adverse or toxic effects
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These include, extreme tiredness, a lack of energy, pins and needles, muscle weakness, disturbed vision, mouth ulcers, a sore and red tongue, and cognitive or psychological concerns such as depression, confusion, and difficulty with memory, understanding or judgement
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They note that the intravenous administration of vitamins or products that are prescription only medicine that are used to improve or enhance wellbeing constitutes treatment of a disease or disorder, and therefore healthcare professionals need to register with the CQC