Vitamin C is good for protecting cells and keeping them healthy, but you should be aware of some ‘overdose’ symptoms
Charlotte Smith Senior Lifestyle Content Editor
11:18, 26 Jan 2026
People who take the vitamin often are being made aware of the possible overdose side effect symptoms(Image: Getty)
People who regularly take vitamin C are advised to discontinue use if they experience specific symptoms, according to the NHS and various health professionals. This vitamin is widely used by millions in the UK and is a favoured option for boosting the immune system, potentially reducing the severity of a cold.
January marks a high season for coughs and colds, along with the prevalence of ‘winter bug’ viruses such as norovirus. In addition to maintaining good hygiene practices every day, ensuring your immune system is functioning optimally is another effective method to safeguard yourself against unpleasant illnesses.
Maintaining a balanced diet is the most effective way to provide your body with everything it requires to combat germs. For some, receiving additional support through a vitamin supplement, particularly if recommended by their physician, can also be beneficial.
Vitamin C is a powerful antioxidant that protects cells from damage caused by free radicals and bolsters the immune system. Additionally, it plays a crucial role in collagen production, which is essential for the health of skin, blood vessels, bones, and cartilage. Furthermore, it enhances the body’s ability to absorb iron and aids in wound healing. A deficiency in vitamin C can result in scurvy.
The NHS says: “Adults aged 19 to 64 need 40mg of vitamin C a day. You should be able to get all the vitamin C you need from your daily diet. Vitamin C cannot be stored in the body, so you need it in your diet every day.”
One side effect symptom is diarrhoea(Image: )
Gut problems and the four symptoms to be aware of
Consuming high doses (over 1,000mg daily) of vitamin C can lead to side effects. According to the NHS, these symptoms should fade once you discontinue vitamin C supplements; however, some cases may require medical attention.
The side effects include, first and foremost, diarrhoea. Additionally, people might face three other issues, including nausea, flatulence, and stomach cramps. This occurs because the body cannot absorb excessive amounts, resulting in an osmotic effect within the digestive tract. Typically, the symptoms subside if you reduce the dosage or stop taking the supplements altogether.
Kidney stones and seven symptoms to watch out for
Another risk of taking too much vitamin C is kidney stones. The NHS says: “Your body will absorb any Vitamin C in your diet and convert it to oxalate, which then goes on to form stones in your kidneys. You should not need to take vitamin supplements if you have a varied diet including fruit and vegetables.”
Taking too much could put you at risk of kidney stones(Image: )
Consuming large amounts of vitamin C supplements (typically over 1,000 mg daily) can increase the risk of developing calcium oxalate kidney stones. This occurs because the body converts excess vitamin C into oxalate, which is subsequently excreted in the urine. While vitamin C from food is considered safe, taking high doses in supplements can lead to elevated oxalate levels in urine. Individuals with a history of kidney stones are frequently advised to avoid these supplements.
According to the NHS, very small kidney stones are “unlikely” to cause many symptoms. It adds: “They may even go undetected and pass out painlessly when you urinate”. However, larger kidney stones can cause symptoms, including the following seven warning signs:
pain in the side of your tummy (abdomen) or groin – men may have pain in their testiclesa high temperature, or feeling hot, cold or shiveryfeeling sweatysevere pain that comes and goesfeeling sick or vomitingblood in your urineurine infection
Some foods are high in oxalate. Too much oxalate-rich food may increase your risk of forming another kidney stone, so where possible, avoid the following foods if you need to take vitamin C daily: rhubarb, wheat bran, berries (such as strawberries, raspberries, and blackberries), spinach, leek, okra, celery, nuts, malted milk drinks, and chocolate.
Speak to your doctor if you are taking vitamin C and experience any of these eleven symptoms, or if you have any health questions or concerns. Avoid making any drastic diet and lifestyle changes before consulting your GP.
The Department of Health and Social Care says you should be able to get all the vitamin C you need by eating a varied and balanced diet. If you take vitamin C supplements, do not take too much, as this could be harmful. Taking less than 1,000mg of vitamin C supplements a day is unlikely to cause any harm.
Good sources of vitamin C
Vitamin C is found in a wide variety of fruit and vegetables. Good sources include:
citrus fruit, such as oranges and orange juicepeppersstrawberriesblackcurrantsbroccolibrussels sproutspotatoes