The NHS is urging people who take vitamin C supplements to stop if they experience any of 11 symptoms, warning that high doses can cause side effects such as diarrhoea, nausea, flatulence, stomach cramps, and kidney stones.
Vitamin C is a popular supplement taken by millions in the UK to boost the immune system, especially during winter when coughs, colds, and norovirus are common. However, the NHS advises that adults aged 19 to 64 need only 40mg per day, which can be obtained from a balanced diet.
Taking more than 1,000mg per day can lead to side effects. The body cannot absorb excess vitamin C, causing digestive issues like diarrhoea and stomach cramps. These symptoms usually resolve when the dosage is reduced or stopped.
A more serious risk is kidney stones. Excess vitamin C is converted to oxalate, which can form calcium oxalate stones in the kidneys. The NHS notes that small stones may pass unnoticed, but larger stones can cause severe pain, blood in urine, and other symptoms requiring medical attention.
The 11 symptoms to watch for include diarrhoea, nausea, flatulence, stomach cramps, and seven signs of kidney stones: pain in the back or side, pain spreading to the lower abdomen, pain during urination, pink or red urine, nausea and vomiting, frequent urination, and fever or chills. Anyone experiencing these should consult a doctor.
The Department of Health and Social Care emphasises that a varied diet provides sufficient vitamin C, and supplements should not exceed 1,000mg daily to avoid harm. Good dietary sources include citrus fruits, berries, kiwi, peppers, broccoli, and Brussels sprouts.
