Vitamin C
Ascorbic acid
A water-soluble vitamin used to prevent and treat vitamin C deficiency (scurvy), which also acts as an antioxidant and helps the body absorb iron.
What is Ascorbic acid?
Ascorbic acid is vitamin C, a water-soluble vitamin the body needs for healthy skin, blood vessels, wound healing and the immune system. Supplements are used mainly to prevent and treat vitamin C deficiency, known as scurvy, and it also helps the body absorb iron from food. It is one of the safest vitamins because the body simply passes any excess out in the urine, though taking very large amounts can cause stomach upset and may slightly raise the risk of kidney stones in some people. Most people get plenty from a balanced diet rich in fruit and vegetables, so supplements are mainly for those who fall short.
Education and reference only. This is a plain-language guide to Ascorbic acid — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Ascorbic acid is the chemical name for vitamin C, a water-soluble vitamin found in many foods, especially citrus fruits, berries, peppers, broccoli and potatoes. The body cannot make or store it in large amounts, so a regular supply from the diet is needed. It is important for making collagen, the protein that supports skin, blood vessels, bones and gums, and it helps wounds heal and supports the immune system. As a supplement it is taken to prevent or treat deficiency, and it is sold widely over the counter.
How it works
Vitamin C acts as a building block for collagen and as an antioxidant that helps protect cells from damage. When deficiency is corrected, the body can once again repair tissues, keep blood vessels and gums healthy and heal wounds properly, so the symptoms of scurvy settle. It also changes iron in food into a form the gut absorbs more easily, which is why a vitamin C-rich drink can help iron supplements work better. Because it dissolves in water, any amount the body does not need is removed in the urine rather than stored.
Company & origin
Originated / developed by: Generic (widely available).
Vitamin C was identified in the 1930s during research into scurvy, a disease long known to affect sailors who lacked fresh fruit and vegetables.
Practical use
How to take Ascorbic acid
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it as advised, usually once a day, with or without food.
- A vitamin C drink or tablet taken with an iron supplement can help your body absorb the iron.
- There is no need to take very large amounts, as the body simply passes out what it does not need.
- If large amounts upset your stomach or loosen your bowels, reduce the amount or take it with food.
- Most people get enough from a balanced diet, so use supplements mainly if you fall short or have been advised to.
Weighing it up
Advantages & disadvantages of Ascorbic acid
Advantages
- Effectively prevents and treats vitamin C deficiency (scurvy) and supports healthy skin, gums and wound healing.
- Very safe and well tolerated, as the body removes any excess in the urine.
- Helps the body absorb iron from food and supplements.
Disadvantages
- Large amounts can cause stomach upset, wind or diarrhoea.
- Very high intake may slightly raise the risk of kidney stones in some people.
- Rarely needed by people who eat a balanced diet, so supplements are often unnecessary.
Practical use
Good to know
Vitamin C is one of the most reassuringly safe vitamins, because the body passes out what it does not need rather than storing it. Most people get plenty from a normal diet, so supplements are mainly useful for people who eat little fruit and vegetables, who smoke, or who have a higher need. Taking very large amounts is not automatically better and can cause stomach upset, wind or diarrhoea, and in some people may slightly increase the risk of kidney stones, so there is no benefit in megadoses. It can help the body absorb iron, so it is sometimes taken alongside iron supplements. Very high intake can also interfere with some home blood-sugar and urine tests, so mention it if you use these.
Who should not take it / use with caution
- People prone to certain kidney stones should avoid very high amounts unless advised.
- Those with iron-overload conditions such as haemochromatosis should be cautious, as it increases iron absorption.
- People with the inherited blood condition G6PD deficiency should avoid very large amounts unless advised.
Monitoring
- Reviewing whether a supplement is actually needed or whether diet can provide enough.
- Checking that symptoms of deficiency improve when it is given for scurvy.
- Considering kidney-stone risk in people taking very large amounts long term.
Side effects
- Usually none at sensible amounts; large amounts can cause stomach upset, wind or diarrhoea.
- Occasional heartburn or nausea.
- Very large amounts may, in some people, contribute to kidney stones.
Key interactions
- Increases the absorption of iron, which can be helpful or, in iron-overload conditions, unwanted.
- Very high intake can interfere with some blood-sugar and urine tests, giving misleading results.
- May slightly affect the action of certain medicines, so tell your prescriber what you take.
Available as: Tablets, including chewable and effervescent forms, taken by mouth.
Answers
Ascorbic acid: frequently asked questions
What is vitamin C used for?
It is mainly used to prevent and treat vitamin C deficiency (scurvy), and it also acts as an antioxidant and helps the body absorb iron from food.
Can I take too much vitamin C?
The body passes out what it does not need, so it is very safe, but large amounts can cause stomach upset and may slightly raise the risk of kidney stones in some people, so megadoses are not helpful.
Does it help with colds?
Vitamin C is important for the immune system, but for most people taking extra does not reliably prevent colds; a balanced diet usually provides what you need.
Should I take it with my iron tablet?
Yes, taking vitamin C with iron can help your body absorb the iron more easily.
Do I need a supplement if I eat fruit and vegetables?
Most people who eat a balanced diet get plenty of vitamin C, so supplements are mainly useful for those who fall short or have been advised to take them.
Authoritative sources
- BNF
- NICE CKS
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