Vitamin C supplements: daily dose and its benefits

Vitamin C is probably the first supplement most of us ever took. Maybe it was a fizzy tablet at the first sign of a sniffle.

But do you actually need vitamin C tablets? If you eat plenty of fruit and veg, probably not. For some people, though, they're a useful backup.

We've looked at what vitamin C does, how much you need and who's most likely to benefit. We've also busted a few myths along the way.

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• What does vitamin C do?
• Benefits of vitamin C
• Vitamin C and colds: what the research says
• How much vitamin C do you need a day?
• Vitamin C deficiency: signs to look out for
• Who needs vitamin C tablets?
• Is 1,000mg of vitamin C too much?
• How to take vitamin C tablets
• Frequently asked questions

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What does vitamin C do?

Vitamin C is a busy little nutrient. It has a hand in your immune system, your skin and how you absorb iron.

It's also known as ascorbic acid. That's the name you'll usually see on supplement labels.

Your body can't make vitamin C or store it.¹ It's water-soluble, so you need a fresh supply every day.

Fortunately, it's found in lots of everyday foods. Good sources include:¹

• citrus fruit, like oranges and orange juice
• peppers, broccoli and brussels sprouts
• strawberries and blackcurrants
• potatoes

Vitamin C breaks down with heat. So steaming veg, or eating some of it raw, helps you hold on to more of it.

Benefits of vitamin C

Vitamin C has more confirmed health claims than most nutrients.²

Immune system. Vitamin C contributes to the normal function of the immune system.²

Training hard? Vitamin C contributes to maintain the normal function of the immune system during and after intense physical exercise.² This one applies at 200mg a day on top of your usual intake.

Tiredness. Vitamin C contributes to the reduction of tiredness and fatigue.² It also contributes to normal energy-yielding metabolism.²

Skin. Vitamin C contributes to normal collagen formation for the normal function of skin.² The same goes for your bones, cartilage, gums, teeth and blood vessels.

Iron. Vitamin C increases iron absorption.² That's handy if you get most of your iron from plants, like beans, lentils and leafy greens.

Protecting cells. Vitamin C contributes to the protection of cells from oxidative stress.²

Mind and nerves. Vitamin C contributes to normal psychological function.² It also contributes to normal functioning of the nervous system.²

One thing worth knowing: these benefits come from having enough vitamin C. Taking loads more than you need won't give you extra benefit.

Vitamin C and colds: what the research says

Reaching for vitamin C when everyone at work is sniffling? Here's what the research actually says.

The biggest review so far looked at dozens of trials.³ In the general population, taking vitamin C every day didn't reduce how often people caught colds.

There was a small effect on how long colds lasted. In people already taking it regularly, adults' colds were around 8% shorter on average.³ That's roughly half a day on a week-long cold.

Taking vitamin C only once a cold had started showed no consistent effect.³

The one group that stood out? People under short bursts of extreme physical stress. In five trials with marathon runners, skiers and soldiers, the risk of catching a cold roughly halved.³ That's a small, specific group, so the findings don't apply to everyone.

So, short answer? Vitamin C won't stop you catching a cold. It still matters for your immune system. Just don't expect a tablet to keep colds away.

How much vitamin C do you need a day?

In the UK, adults aged 19 to 64 need 40mg of vitamin C a day.¹ That's the same for men and women.

You should be able to get all of that from a varied diet.¹ A glass of orange juice, a pepper in your stir-fry or a portion of broccoli soon adds up.

You might see higher numbers elsewhere. In the US, the recommendation is 90mg for men and 75mg for women.⁴ Some researchers have argued the UK figure is due a review.⁵ For now, though, 40mg is the official UK guidance.

Some people need a bit more:

• Smokers: smoking uses up vitamin C faster. US guidance suggests smokers need an extra 35mg a day.⁴
• Pregnancy and breastfeeding: your needs go up a little at these times.⁴

Vitamin C deficiency: signs to look out for

Severe vitamin C deficiency is called scurvy. Yes, the one sailors used to get.

It's rare in the UK, because most people get enough from their diet.⁶ It usually takes at least three months of very low intake to develop.⁶

Signs of scurvy can include:⁶

• feeling very tired and weak all the time
• feeling irritable or low
• joint, muscle or leg pain
• swollen, bleeding gums
• red or blue spots on the skin, often on the shins
• bruising easily

If you think you might have signs of scurvy, speak to your GP. They may suggest a blood test to check.

Who needs vitamin C tablets?

While you'll likely get enough vitamin C if you eat a varied diet, some people will find it harder to hit that target.

You're more likely to fall short if you:⁶

• Don't eat much fruit or veg: whether that's a busy schedule or just not liking them.
• Smoke: smoking reduces how much vitamin C your body gets from food.
• Eat very little or follow a very restricted diet: including during some medical treatments.
• Are older and finding it hard to eat well: a smaller appetite can mean fewer fruit and veg.

If you have a condition that affects how you absorb nutrients, speak to your GP before taking a supplement.

OneVit Vitamin C gives you 1,000mg of vitamin C in one tablet a day. It's suitable for vegetarians and vegans.

Think of supplements as backup, not a replacement for a decent diet though.

Is 1,000mg of vitamin C too much?

It's a fair question, since 1,000mg is way more than 40mg. Here's what the NHS says.

Taking less than 1,000mg of vitamin C supplements a day is unlikely to cause any harm.¹ Taking more than 1,000mg a day can cause stomach pain, diarrhoea and wind.¹ These symptoms should go away once you stop.

So a single 1,000mg tablet sits right on the line. Do not take more than one tablet a day.

The trickier bit is doubling up. Vitamin C turns up in multivitamins, fizzy immune drinks and some collagen supplements. For example, OneVit Marine Collagen Complex already contains some vitamin C.

If you already take a multivitamin or another supplement, check the label before adding vitamin C tablets.

Who should be careful

High doses aren't right for everyone. Speak to your GP or pharmacist before taking vitamin C supplements if you:

• Have had kidney stones: high doses may raise the risk in people prone to them.⁷
• Have haemochromatosis: this condition causes iron build-up, and vitamin C increases iron absorption.⁷
• Are having cancer treatment: antioxidant supplements may need checking with your care team first.⁴
• Take any regular medicines.

If you are pregnant or breastfeeding, speak to your GP, midwife or pharmacist before taking a high-strength vitamin C supplement.

If you notice side effects, stop taking it and speak to a pharmacist.

How to take vitamin C tablets

There's no magic time of day. The best time is whenever you'll remember it.

A few tips:

• Take it daily: your body doesn't store vitamin C, so regular beats occasional.¹
• Take it with food if it upsets your stomach: a meal can make it easier to tolerate.
• Swallow with water: stick to the dose on the label.

Taking vitamin C with iron

Vitamin C increases iron absorption.² So if you take an iron supplement, pairing them up makes sense.

OneVit Iron can be taken alongside vitamin C. Just remember the one-tablet rule if your iron supplement already contains vitamin C.

If tiredness is not improving, speak to your GP. Low iron is just one of many possible causes, and a blood test can check.

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Frequently asked questions

Is it OK to take vitamin C every day? Yes, for most adults. Your body can't store vitamin C, so you need some every day.¹ Taking less than 1,000mg a day from supplements is unlikely to cause harm.¹

How much vitamin C per day for a woman? In the UK, women aged 19 to 64 need 40mg a day, the same as men.¹ Needs go up a little during pregnancy and breastfeeding. A varied diet usually covers it.

Can you take too much vitamin C? Yes. More than 1,000mg a day can cause stomach pain, diarrhoea and wind.¹ Watch out for doubling up across several supplements.

Can you take vitamin C and zinc together? Yes, many people do, and they're often sold together. Just check the total vitamin C across everything you take stays at or under 1,000mg a day.

What's the best time to take vitamin C tablets? Whenever suits you. If it upsets your stomach, try taking it with a meal.

Does vitamin C help with tiredness? Vitamin C contributes to the reduction of tiredness and fatigue.² But tiredness has lots of possible causes. If it is not improving, speak to your GP.

What should I look for in a vitamin C supplement? Check the dose per tablet and how many you take a day. Then check what else you already take that contains vitamin C. A single daily tablet makes it easier to keep track.

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References

1. NHS. Vitamins and minerals: Vitamin C. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-c/
2. GOV.UK. Great Britain nutrition and health claims (NHC) register. https://www.gov.uk/guidance/great-britain-nutrition-and-health-claims-nhc-register
3. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. 2013;(1):CD000980. https://www.cochrane.org/CD000980/ARI_vitamin-c-for-the-common-cold
4. National Institutes of Health, Office of Dietary Supplements. Vitamin C: Fact Sheet for Consumers. https://ods.od.nih.gov/factsheets/vitaminc-consumer/
5. Hemilä H. Are the UK's vitamin C recommendations evidence-based? A critical comment. British Journal of Nutrition. 2025. https://resolve.cambridge.org/core/journals/british-journal-of-nutrition/article/are-the-uks-vitamin-c-recommendations-evidencebased-a-critical-comment/56CF5CC90AA57D0421FEF55E36556D8B
6. NHS. Scurvy. https://www.nhs.uk/conditions/scurvy/
7. Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Vitamin C. National Academies Press; 2006. https://nap.edu/read/11537/chapter/21

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This article is for informational purposes only and does not constitute medical advice. If you are concerned about your vitamin C intake, consult a GP or qualified healthcare professional.